Merge pull request 'Adding in sandbox + Logger upgrade' (#80) from sandbox into main

Reviewed-on: #80

.clocignore

@@ -0,0 +1,8 @@
+third_party
+build
+__dump
+traces
+.vscode
+.claude
+.git
+imgui.ini

.gitea/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,31 @@
+---
+name: Bug report
+about: Create a report to help us improve
+title: ""
+labels: ""
+assignees: ""
+---
+
+**Desktop (please complete the following information):**
+
+- OS: [e.g. iOS]
+- Browser [e.g. chrome, safari]
+- Version [e.g. 22]
+
+**Describe the bug**
+A clear and concise description of what the bug is.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+
+1. Something
+2. ...
+
+**Expected behavior**
+A clear and concise description of what you expected to happen.
+
+**Screenshots**
+If applicable, add screenshots to help explain your problem.
+
+**Additional context**
+Add any other context about the problem here.

.gitea/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,23 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+title: ""
+labels: ""
+assignees: ""
+---
+
+Relates to:
+
+- TODO
+
+## Context
+
+TODO
+
+## Implementation
+
+TODO
+
+## Additional resources
+
+TODO

.gitea/pull_request_template.md

@@ -0,0 +1,17 @@
+resolves TODO
+
+## Context
+
+TODO
+
+## Implementation
+
+TODO
+
+## Screenshots
+
+TODO
+
+## Testing Instructions
+
+1. Build engine and run editor via `bin/dev editor`

.gitignore

@@ -24,7 +24,6 @@ CMakeUserPresets.json
 *.bin
 *.out
 *.spv
-*.spv.h
 
 # Runtime data
 pids
@@ -33,6 +32,13 @@ pids
 *.pid.lock
 imgui.ini
 
+# Python bytecode (bin/dev and bin/dev_commands)
+__pycache__/
+
+# Tracy captures
+traces/
+*.tracy
+
 # dotenv environment variables file
 .envrc
 .env

.gitmodules

@@ -8,3 +8,9 @@
 	path = third_party/imgui
 	url = https://github.com/ocornut/imgui.git
 	branch = docking
+[submodule "third_party/tracy"]
+	path = third_party/tracy
+	url = https://github.com/wolfpld/tracy.git
+[submodule "third_party/ImGuizmo"]
+	path = third_party/ImGuizmo
+	url = https://github.com/CedricGuillemet/ImGuizmo.git

.vscode/settings.json

@@ -41,8 +41,8 @@
     "LD_LIBRARY_PATH": "/home/caleb/.local/share/vulkan-sdk/1.4.357.1/x86_64/lib/VulkanLoader/lib:/home/caleb/.local/share/vulkan-sdk/1.4.357.1/x86_64/lib",
     "VK_ADD_LAYER_PATH": "/home/caleb/.local/share/vulkan-sdk/1.4.357.1/x86_64/share/vulkan/explicit_layer.d"
   },
-  "cmake.buildDirectory": "${workspaceFolder}/build",
+  "cmake.useCMakePresets": "always",
-  "cmake.generator": "Ninja",
+  "cmake.copyCompileCommands": "${workspaceFolder}/build/compile_commands.json",
   "cmake.configureOnOpen": true,
   "files.associations": {
     ".clang-format": "yaml",

CLAUDE.md

@@ -0,0 +1,17 @@
+# Sophia
+
+## Dev helper (`bin/dev`)
+
+`bin/dev` wraps common project tasks. Run `bin/dev bash-completions` to list commands.
+
+### Creating issues
+
+Use `bin/dev issue` to create Gitea issues instead of calling the API or `tea` directly:
+
+```sh
+bin/dev issue "<title>" [-b "<body>"] [-l <label>]... [-a <user>]... [--open]
+```
+
+- Labels are repo label names (`bug`, `enhancement`, `question`, ...).
+- The Gitea API cannot add an issue to a project. After creating an issue, tell the user its URL so they can add it to the "sophia" project (issue sidebar > Projects), or pass `--open`.
+- Only create issues when the user asks; issues are visible on the remote.

CMakeLists.txt

@@ -1,11 +1,11 @@
-cmake_minimum_required(VERSION 3.22.2)
+cmake_minimum_required(VERSION 3.25.2)
 
 set(NAME sophia)
 
 project(${NAME} VERSION 0.0.0)
 
 enable_language(CXX)
-set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_STANDARD 23)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
@@ -15,8 +15,6 @@ endif()
 
 if(CMAKE_BUILD_TYPE STREQUAL "Debug")
   message(STATUS "Debug build: enabling debug logging")
-else()
-  add_compile_definitions(NDEBUG)
 endif()
 
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
@@ -39,5 +37,7 @@ endif()
 
 add_subdirectory(third_party)
 add_subdirectory(engine)
+add_subdirectory(editor)
 add_subdirectory(testbed)
+add_subdirectory(sandbox)
 add_subdirectory(examples)

CMakePresets.json

@@ -0,0 +1,66 @@
+{
+  "version": 6,
+  "configurePresets": [
+    {
+      "name": "base",
+      "hidden": true,
+      "generator": "Ninja",
+      "binaryDir": "${sourceDir}/build/${presetName}",
+      "cacheVariables": {
+        "CMAKE_EXPORT_COMPILE_COMMANDS": "ON"
+      }
+    },
+    {
+      "name": "debug",
+      "displayName": "Debug",
+      "inherits": "base",
+      "cacheVariables": {
+        "CMAKE_BUILD_TYPE": "Debug"
+      }
+    },
+    {
+      "name": "release",
+      "displayName": "Release (with debug info)",
+      "inherits": "base",
+      "cacheVariables": {
+        "CMAKE_BUILD_TYPE": "RelWithDebInfo"
+      }
+    },
+    {
+      "name": "asan",
+      "displayName": "Debug + AddressSanitizer/UBSan",
+      "inherits": "debug",
+      "cacheVariables": {
+        "CMAKE_CXX_FLAGS": "-fsanitize=address,undefined -fno-omit-frame-pointer",
+        "CMAKE_C_FLAGS": "-fsanitize=address,undefined -fno-omit-frame-pointer"
+      }
+    },
+    {
+      "name": "tsan",
+      "displayName": "Debug + ThreadSanitizer",
+      "inherits": "debug",
+      "cacheVariables": {
+        "CMAKE_CXX_FLAGS": "-fsanitize=thread",
+        "CMAKE_C_FLAGS": "-fsanitize=thread"
+      }
+    }
+  ],
+  "buildPresets": [
+    {
+      "name": "debug",
+      "configurePreset": "debug"
+    },
+    {
+      "name": "release",
+      "configurePreset": "release"
+    },
+    {
+      "name": "asan",
+      "configurePreset": "asan"
+    },
+    {
+      "name": "tsan",
+      "configurePreset": "tsan"
+    }
+  ]
+}

README.md

@@ -1,5 +1,7 @@
 # sophia
 
+![showcase](./media/showcase.png)
+
 ## Getting Started
 
 COMING SOON
@@ -8,17 +10,21 @@ COMING SOON
 
 ### Dependencies
 
-- [cmake](https://cmake.org/)
+- [cmake](https://cmake.org/) 3.25+
+- [Ninja](https://ninja-build.org/)
 - [Vulkan SDK](https://vulkan.lunarg.com/) - With validation layers
 
 ### Build instructions
 
+Builds use the presets in `CMakePresets.json` (`debug`, `release`), each in its own `build/<preset>` directory:
+
 ```sh
-cmake -S . -B build -DCMAKE_BUILD_TYPE=Debug
+cmake --preset debug
-cd build
+cmake --build --preset debug
-make -j
 ```
 
+Or with the dev helper: `dev build [preset] [--fresh]`.
+
 ## Third Party libraries used
 
 - [GLFW](https://github.com/glfw/glfw) - Window and input handling

bin/dev

@@ -1,21 +1,28 @@
 #!/usr/bin/env python3
 
+import json
 import os
-import re
+import shlex
 import shutil
-import struct
 import subprocess
 import sys
 
+from helpers.gitea import GiteaCommand
+from helpers.renderdoc import RenderDocCommand
+from helpers.shaders import ShadersCommand
+from helpers.tracy import TracyCommand
+
 COMMAND_TO_METHOD = {
+    "branch-from": "branch_from",
     "bash-completions": "bash_completions",
 }
 METHOD_TO_COMMAND = {method: command for command, method in COMMAND_TO_METHOD.items()}
 
 WAIT_FOR_PROCESS = "wait_for_process"
 
-class DevHelper:
+class DevCommand(GiteaCommand, RenderDocCommand, ShadersCommand, TracyCommand):
-    SHADER_EXTENSIONS = (".vert", ".frag", ".comp", ".geom", ".tesc", ".tese")
+    PROJECT_NAME = "sophia"
+    DEFAULT_PRESET = "debug"
 
     def __init__(self):
         self.last_exit_status = 0
@@ -23,6 +30,9 @@ class DevHelper:
     # Core logic
     def call(self, *args, **kwargs):
         if not args:
+            print("Usage: dev <command> [args...]\n\nCommands:")
+            for command in self._commands():
+                print(f"  {command}")
             return
 
         command, rest = args[0], args[1:]
@@ -32,37 +42,67 @@ class DevHelper:
             return method(*rest, **kwargs)
 
     # Primary command wrappers
+
+    ##
+    # Configures and builds a CMake preset (see CMakePresets.json).
+    #   dev build [preset] [--fresh]
+    # The preset defaults to debug and builds into build/<preset>. --fresh
+    # discards the preset's CMake cache before configuring.
     def build(self, *args, **kwargs):
-        command = f"rm -rf build && cmake -S . -B build -DCMAKE_BUILD_TYPE=Debug"
+        preset, fresh = self._parse_preset_args(args, "build")
-        self._exec_in_root(command, replace=True)
+        self._build_preset(preset, fresh)
 
-    def renderdoc(self, *args, **kwargs):
+    ##
-        qrenderdoc = self._find_qrenderdoc()
+    # Builds the debug preset (incrementally), then runs the editor from
-        self._exec_in_root(qrenderdoc, replace=True)
+    # build/debug. Any arguments are passed through to the editor.
+    #   dev editor [args...]
+    def editor(self, *args, **kwargs):
+        preset = self.DEFAULT_PRESET
+        self._build_preset(preset, fresh=False)
 
-    def shaders(self, *args, **kwargs):
+        preset_dir = os.path.join(self._project_root(), "build", preset)
-        shaders_dir = os.path.join(self._project_root(), "engine", "src", "shaders")
+        binary = os.path.join(preset_dir, "bin", "editor")
-        if not os.path.isdir(shaders_dir):
+        print(f"Running: {shlex.join([binary, *args])}")
-            raise ValueError(f"Shaders directory not found: {shaders_dir}")
+        os.chdir(preset_dir)
+        os.execv(binary, [binary, *args])
 
-        glslc = self._find_glslc()
+    ##
+    # Builds the debug preset (incrementally), then runs the testbed from
+    # build/debug. Any arguments are passed through to the testbed.
+    #   dev testbed [args...]
+    def testbed(self, *args, **kwargs):
+        preset = self.DEFAULT_PRESET
+        self._build_preset(preset, fresh=False)
 
-        shader_paths = sorted(
+        preset_dir = os.path.join(self._project_root(), "build", preset)
-            os.path.join(root, filename)
+        binary = os.path.join(preset_dir, "bin", "testbed")
-            for root, _dirs, files in os.walk(shaders_dir)
+        print(f"Running: {shlex.join([binary, *args])}")
-            for filename in files
+        os.chdir(preset_dir)
-            if filename.endswith(self.SHADER_EXTENSIONS)
+        os.execv(binary, [binary, *args])
-        )
 
-        if not shader_paths:
+    ##
-            print(f"No shaders found in {shaders_dir}")
+    # Builds the debug preset (incrementally), then runs the raw Vulkan
-            return
+    # sandbox from build/debug. Any arguments are passed through.
+    #   dev sandbox [args...]
+    def sandbox(self, *args, **kwargs):
+        preset = self.DEFAULT_PRESET
+        self._build_preset(preset, fresh=False)
 
-        for shader_path in shader_paths:
+        preset_dir = os.path.join(self._project_root(), "build", preset)
-            self._generate_shader_header(glslc, shader_path)
+        binary = os.path.join(preset_dir, "bin", "sandbox")
+        print(f"Running: {shlex.join([binary, *args])}")
+        os.chdir(preset_dir)
+        os.execv(binary, [binary, *args])
 
     # Custom helpers
 
+    ##
+    # Counts lines of code from the project root, skipping paths listed in
+    # .clocignore. Any arguments are passed through to cloc.
+    #   dev cloc [args...]
+    def cloc(self, *args, **kwargs):
+        self._run_in_root(["cloc", "--exclude-list-file=.clocignore", *args, "."])
+
     def ownit(self, *args, **kwargs):
         file_or_directory = args[0] if args else None
         if file_or_directory is None:
@@ -76,83 +116,61 @@ class DevHelper:
             raise NotImplementedError(f"Not implemented for platform {sys.platform}")
 
     def bash_completions(self, *args, **kwargs):
-        completions = sorted(
+        print(" ".join(self._commands()))
-            METHOD_TO_COMMAND.get(name, name)
-            for name in vars(DevHelper)
-            if not name.startswith("_") and name != "call" and callable(getattr(DevHelper, name))
-        )
-        print(" ".join(completions))
 
     # Private helpers
-    def _find_glslc(self):
+    def _commands(self):
-        glslc = shutil.which("glslc")
+        return sorted(
-        if glslc is None:
+            METHOD_TO_COMMAND.get(name, name)
-            raise RuntimeError(
+            for name in dir(DevCommand)
-                "glslc not found on PATH (install the Vulkan SDK)"
+            if not name.startswith("_") and name != "call" and callable(getattr(DevCommand, name))
-            )
-        return glslc
-
-    def _find_qrenderdoc(self):
-        qrenderdoc = shutil.which("qrenderdoc")
-        if qrenderdoc is None:
-            raise RuntimeError(
-                "qrenderdoc not found on PATH (install RenderDoc)"
-            )
-        return qrenderdoc
-
-    def _generate_shader_header(self, glslc, shader_path):
-        relative_path = os.path.relpath(shader_path, self._project_root())
-        print(f"Compiling shader: {relative_path}")
-
-        result = subprocess.run(
-            [glslc, shader_path, "-o", "-"],
-            stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE,
         )
+
+    def _parse_preset_args(self, args, command):
+        preset = None
+        fresh = False
+        for arg in args:
+            if arg == "--fresh":
+                fresh = True
+            elif arg.startswith("-"):
+                raise ValueError(f"Unknown option: {arg}")
+            elif preset is None:
+                preset = arg
+            else:
+                raise ValueError(f"Usage: dev {command} [preset] [--fresh]")
+
+        preset = preset or self.DEFAULT_PRESET
+        presets = self._configure_presets()
+        if preset not in presets:
+            raise ValueError(f"Unknown preset: {preset} (available: {', '.join(presets)})")
+        return preset, fresh
+
+    def _configure_presets(self):
+        with open(os.path.join(self._project_root(), "CMakePresets.json")) as f:
+            presets = json.load(f)["configurePresets"]
+        return [preset["name"] for preset in presets if not preset.get("hidden")]
+
+    def _build_preset(self, preset, fresh):
+        configure = ["cmake", "--preset", preset]
+        if fresh:
+            configure.append("--fresh")
+        self._run_in_root(configure)
+        self._copy_compile_commands(preset)
+        self._run_in_root(["cmake", "--build", "--preset", preset])
+
+    # Editor tooling reads build/compile_commands.json, so point it at the
+    # most recently configured preset.
+    def _copy_compile_commands(self, preset):
+        build_dir = os.path.join(self._project_root(), "build")
+        source = os.path.join(build_dir, preset, "compile_commands.json")
+        if os.path.isfile(source):
+            shutil.copyfile(source, os.path.join(build_dir, "compile_commands.json"))
+
+    def _run_in_root(self, command):
+        print(f"Running: {shlex.join(command)}")
+        result = subprocess.run(command, cwd=self._project_root())
         if result.returncode != 0:
-            raise RuntimeError(
+            sys.exit(result.returncode)
-                f"failed to compile {shader_path}: {result.stderr.decode()}"
-            )
-
-        spirv = result.stdout
-        if len(spirv) % 4 != 0:
-            raise RuntimeError(
-                f"invalid SPIR-V output for {shader_path} (size not a multiple of 4)"
-            )
-
-        word_count = len(spirv) // 4
-        words = struct.unpack(f"<{word_count}I", spirv)
-
-        filename = os.path.basename(shader_path)
-        variable_name = f"{filename.replace('.', '_')}_spv"
-        header_path = shader_path + ".spv.h"
-
-        body_lines = [
-            "    " + ", ".join(f"0x{word:08x}" for word in words[i:i + 4]) + ","
-            for i in range(0, len(words), 4)
-        ]
-
-        header = "\n".join([
-            "#pragma once",
-            "",
-            "#include <array>",
-            "#include <cstdint>",
-            "",
-            "namespace sophia::shaders {",
-            "",
-            f"inline constexpr std::array<uint32_t, {word_count}> {variable_name} = {{",
-            *body_lines,
-            "};",
-            "",
-            "}  // namespace sophia::shaders",
-            "",
-        ])
-
-        with open(header_path, "w") as f:
-            f.write(header)
-
-        print(f"Wrote {os.path.relpath(header_path, self._project_root())} "
-              f"({word_count * 4} bytes)")
 
     def _wait_for_process_with_logging(self, command):
         process = self._exec(command, capture=True)
@@ -197,4 +215,4 @@ class DevHelper:
 
 
 if __name__ == "__main__":
-    DevHelper().call(*sys.argv[1:])
+    DevCommand().call(*sys.argv[1:])

bin/helpers/gitea.py

@@ -0,0 +1,156 @@
+import json
+import re
+import shlex
+import shutil
+import subprocess
+import sys
+
+
+# Mixed into DevCommand (bin/dev), which provides PROJECT_NAME, _project_root
+# and _exec_in_root.
+class GiteaCommand:
+    ##
+    # Checks out a branch named after a Gitea issue URL.
+    # If the issue is from this project's repo, the branch name will be:
+    #   issue-<issue_number>/<issue_title>
+    # If the issue is from another repo (presumably upstream), the branch name will be:
+    #   <issue_owner>-issue-<issue_number>/<issue_title>
+    def branch_from(self, *args, **kwargs):
+        issue_url = args[0] if args else None
+        if issue_url is None:
+            raise ValueError("Must provide a Gitea issue URL.")
+
+        base_url, issue_repo, issue_number = self._parse_issue_url(issue_url)
+        issue_title = self._fetch_issue_title(base_url, issue_repo, issue_number)
+        branch_name = self._format_branch_name(issue_repo, issue_number, issue_title)
+
+        exists = subprocess.run(
+            ["git", "-C", self._project_root(), "rev-parse", "--verify", "--quiet", f"refs/heads/{branch_name}"],
+            stdout=subprocess.DEVNULL,
+        ).returncode == 0
+        flag = "" if exists else "-b "
+        self._exec_in_root(f"git checkout {flag}{shlex.quote(branch_name)}", replace=True)
+
+    ##
+    # Creates an issue on this project's Gitea repo.
+    #   dev issue <title> [-b|--body <text>] [-l|--label <name>]... [-a|--assignee <user>]... [-o|--open]
+    # The body is read from stdin if --body is not given and stdin is piped.
+    # Gitea's API cannot add issues to a project (only the web UI can), so the
+    # issue URL is printed and --open opens it in the browser to do so.
+    def issue(self, *args, **kwargs):
+        title, body, labels, assignees, open_in_browser = self._parse_issue_args(args)
+
+        repo = self._origin_repo()
+        if repo is None:
+            raise RuntimeError("could not determine the Gitea repo from the origin remote")
+
+        payload = {"title": title, "body": body}
+        if labels:
+            label_ids = self._fetch_label_ids(repo)
+            unknown = [label for label in labels if label not in label_ids]
+            if unknown:
+                raise ValueError(f"Unknown label(s): {', '.join(unknown)} (available: {', '.join(sorted(label_ids))})")
+            payload["labels"] = [label_ids[label] for label in labels]
+        if assignees:
+            payload["assignees"] = assignees
+
+        issue = self._tea_api(f"repos/{repo}/issues", payload)
+        print(f"Created issue #{issue['number']}: {issue['title']}")
+        print(issue["html_url"])
+        print(f"Add it to the project from the issue sidebar: Projects > {self.PROJECT_NAME}")
+
+        if open_in_browser:
+            opener = shutil.which("xdg-open") or shutil.which("open")
+            if opener is None:
+                raise RuntimeError("xdg-open not found on PATH")
+            subprocess.Popen([opener, issue["html_url"]], stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+
+    def _parse_issue_url(self, url):
+        match = re.match(r"^(https?://[^/]+)/([^/]+)/([^/]+)/issues/(\d+)", url)
+        if match is None:
+            raise ValueError(f"Not a Gitea issue URL: {url}")
+        return match[1], f"{match[2]}/{match[3]}", match[4]
+
+    def _fetch_issue_title(self, base_url, repo, issue_number):
+        if shutil.which("tea") is None:
+            raise RuntimeError("tea not found on PATH (install gitea tea and run `tea login add`)")
+
+        endpoint = f"{base_url}/api/v1/repos/{repo}/issues/{issue_number}"
+        print(f"Running: tea api {endpoint}")
+        result = subprocess.run(["tea", "api", endpoint], stdout=subprocess.PIPE, text=True)
+        if result.returncode != 0:
+            raise RuntimeError(f"failed to fetch issue title from {endpoint}")
+        return json.loads(result.stdout)["title"]
+
+    def _parse_issue_args(self, args):
+        title = None
+        body = None
+        labels = []
+        assignees = []
+        open_in_browser = False
+
+        args = list(args)
+        while args:
+            arg = args.pop(0)
+            if arg in ("-b", "--body", "-l", "--label", "-a", "--assignee"):
+                if not args:
+                    raise ValueError(f"{arg} requires a value")
+                value = args.pop(0)
+                if arg in ("-b", "--body"):
+                    body = value
+                elif arg in ("-l", "--label"):
+                    labels.append(value)
+                else:
+                    assignees.append(value)
+            elif arg in ("-o", "--open"):
+                open_in_browser = True
+            elif arg.startswith("-"):
+                raise ValueError(f"Unknown option: {arg}")
+            elif title is None:
+                title = arg
+            else:
+                title = f"{title} {arg}"
+
+        if not title:
+            raise ValueError("Must provide an issue title. Usage: dev issue <title> [-b <body>] [-l <label>]... [-a <user>]... [-o]")
+        if body is None:
+            body = "" if sys.stdin.isatty() else sys.stdin.read()
+        return title, body, labels, assignees, open_in_browser
+
+    def _tea_api(self, endpoint, payload=None):
+        if shutil.which("tea") is None:
+            raise RuntimeError("tea not found on PATH (install gitea tea and run `tea login add`)")
+
+        command = ["tea", "api", endpoint]
+        if payload is not None:
+            command += ["-d", "@-"]
+        print(f"Running: {' '.join(command)}")
+        result = subprocess.run(
+            command,
+            input=json.dumps(payload) if payload is not None else None,
+            stdout=subprocess.PIPE,
+            text=True,
+        )
+        if result.returncode != 0:
+            raise RuntimeError(f"tea api request failed: {endpoint}")
+        return json.loads(result.stdout)
+
+    def _fetch_label_ids(self, repo):
+        labels = self._tea_api(f"repos/{repo}/labels?limit=100")
+        return {label["name"]: label["id"] for label in labels}
+
+    def _format_branch_name(self, issue_repo, issue_number, issue_title):
+        formatted_title = re.sub(r"-+", "-", re.sub(r"[^a-z0-9\-]", "", re.sub(r"\s+", "-", issue_title.lower().strip())))
+        if issue_repo == self._origin_repo():
+            return f"issue-{issue_number}/{formatted_title}"
+        issue_owner = issue_repo.split("/")[0]
+        return f"{issue_owner}-issue-{issue_number}/{formatted_title}"
+
+    def _origin_repo(self):
+        result = subprocess.run(
+            ["git", "-C", self._project_root(), "remote", "get-url", "origin"],
+            stdout=subprocess.PIPE,
+            text=True,
+        )
+        match = re.search(r"[:/]([^/:]+/[^/]+?)(?:\.git)?$", result.stdout.strip())
+        return match[1] if match else None

bin/helpers/renderdoc.py

@@ -0,0 +1,16 @@
+import shutil
+
+
+# Mixed into DevCommand (bin/dev), which provides _exec_in_root.
+class RenderDocCommand:
+    def renderdoc(self, *args, **kwargs):
+        qrenderdoc = self._find_qrenderdoc()
+        self._exec_in_root(qrenderdoc, replace=True)
+
+    def _find_qrenderdoc(self):
+        qrenderdoc = shutil.which("qrenderdoc")
+        if qrenderdoc is None:
+            raise RuntimeError(
+                "qrenderdoc not found on PATH (install RenderDoc)"
+            )
+        return qrenderdoc

bin/helpers/shaders.py

@@ -0,0 +1,92 @@
+import os
+import shutil
+import struct
+import subprocess
+
+
+# Mixed into DevCommand (bin/dev), which provides _project_root.
+class ShadersCommand:
+    SHADER_EXTENSIONS = (".vert", ".frag", ".comp", ".geom", ".tesc", ".tese")
+
+    def shaders(self, *args, **kwargs):
+        shaders_dir = os.path.join(self._project_root(), "engine", "src", "shaders")
+        if not os.path.isdir(shaders_dir):
+            raise ValueError(f"Shaders directory not found: {shaders_dir}")
+
+        glslc = self._find_glslc()
+
+        shader_paths = sorted(
+            os.path.join(root, filename)
+            for root, _dirs, files in os.walk(shaders_dir)
+            for filename in files
+            if filename.endswith(self.SHADER_EXTENSIONS)
+        )
+
+        if not shader_paths:
+            print(f"No shaders found in {shaders_dir}")
+            return
+
+        for shader_path in shader_paths:
+            self._generate_shader_header(glslc, shader_path)
+
+    def _find_glslc(self):
+        glslc = shutil.which("glslc")
+        if glslc is None:
+            raise RuntimeError(
+                "glslc not found on PATH (install the Vulkan SDK)"
+            )
+        return glslc
+
+    def _generate_shader_header(self, glslc, shader_path):
+        relative_path = os.path.relpath(shader_path, self._project_root())
+        print(f"Compiling shader: {relative_path}")
+
+        result = subprocess.run(
+            [glslc, shader_path, "-o", "-"],
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+        )
+        if result.returncode != 0:
+            raise RuntimeError(
+                f"failed to compile {shader_path}: {result.stderr.decode()}"
+            )
+
+        spirv = result.stdout
+        if len(spirv) % 4 != 0:
+            raise RuntimeError(
+                f"invalid SPIR-V output for {shader_path} (size not a multiple of 4)"
+            )
+
+        word_count = len(spirv) // 4
+        words = struct.unpack(f"<{word_count}I", spirv)
+
+        filename = os.path.basename(shader_path)
+        variable_name = f"{filename.replace('.', '_')}_spv"
+        header_path = shader_path + ".spv.h"
+
+        body_lines = [
+            "    " + ", ".join(f"0x{word:08x}" for word in words[i:i + 4]) + ","
+            for i in range(0, len(words), 4)
+        ]
+
+        header = "\n".join([
+            "#pragma once",
+            "",
+            "#include <array>",
+            "#include <cstdint>",
+            "",
+            "namespace sophia::shaders {",
+            "",
+            f"inline constexpr std::array<uint32_t, {word_count}> {variable_name} = {{",
+            *body_lines,
+            "};",
+            "",
+            "}  // namespace sophia::shaders",
+            "",
+        ])
+
+        with open(header_path, "w") as f:
+            f.write(header)
+
+        print(f"Wrote {os.path.relpath(header_path, self._project_root())} "
+              f"({word_count * 4} bytes)")

bin/helpers/tracy.py

@@ -0,0 +1,85 @@
+import os
+import re
+import shlex
+import time
+
+
+# Mixed into DevCommand (bin/dev), which provides _project_root and
+# _run_in_root.
+class TracyCommand:
+    ##
+    # Builds a Tracy tool from the third_party/tracy submodule, then runs it.
+    # Building from the submodule keeps the tool's version in sync with the
+    # client compiled into the engine.
+    #   dev tracy [--fresh] [args...]           Opens the profiler (viewer).
+    #   dev tracy --save [name] [--fresh] [args...]
+    #                                            Captures a trace headlessly to
+    #                                            traces/<name>.tracy (default
+    #                                            name: a timestamp) until the app
+    #                                            exits or Ctrl+C.
+    # The profiler uses the X11 backend unless WAYLAND_DISPLAY is set. Tools
+    # are configured on first use (or --fresh, or when the backend changes),
+    # then built incrementally. Other arguments are passed through to the tool
+    # (e.g. a .tracy file to open, or `-s 10` to capture for 10 seconds).
+    def tracy(self, *args, **kwargs):
+        fresh, save, name, args = self._parse_tracy_args(args)
+
+        if save:
+            binary = self._build_tracy_tool("capture", "tracy-capture", {}, fresh)
+            traces_dir = os.path.join(self._project_root(), "traces")
+            os.makedirs(traces_dir, exist_ok=True)
+            name = name or time.strftime("%Y-%m-%d-%H%M%S")
+            if not name.endswith(".tracy"):
+                name += ".tracy"
+            args = ["-o", os.path.join(traces_dir, name), *args]
+        else:
+            legacy = "OFF" if os.environ.get("WAYLAND_DISPLAY") else "ON"
+            binary = self._build_tracy_tool("profiler", "tracy-profiler", {"LEGACY": legacy}, fresh)
+
+        print(f"Running: {shlex.join([binary, *args])}")
+        os.execv(binary, [binary, *args])
+
+    def _parse_tracy_args(self, args):
+        fresh = False
+        save = False
+        name = None
+        rest = []
+
+        args = list(args)
+        while args:
+            arg = args.pop(0)
+            if arg == "--fresh":
+                fresh = True
+            elif arg == "--save":
+                save = True
+                if args and not args[0].startswith("-"):
+                    name = args.pop(0)
+            else:
+                rest.append(arg)
+        return fresh, save, name, rest
+
+    # Configures third_party/tracy/<tool> into <tool>/build when it has no
+    # build yet, --fresh is given, or a cached define differs from `defines`.
+    def _build_tracy_tool(self, tool, binary_name, defines, fresh):
+        source_dir = os.path.join("third_party", "tracy", tool)
+        build_dir = os.path.join(source_dir, "build")
+        cache_path = os.path.join(self._project_root(), build_dir, "CMakeCache.txt")
+
+        stale = not os.path.isfile(cache_path)
+        if not stale:
+            with open(cache_path) as f:
+                cache = f.read()
+            stale = any(
+                re.search(rf"^{key}:BOOL={value}$", cache, re.MULTILINE) is None
+                for key, value in defines.items()
+            )
+
+        if fresh or stale:
+            configure = ["cmake", "-B", build_dir, "-S", source_dir, "-DCMAKE_BUILD_TYPE=Release"]
+            configure += [f"-D{key}={value}" for key, value in defines.items()]
+            if fresh:
+                configure.append("--fresh")
+            self._run_in_root(configure)
+        self._run_in_root(["cmake", "--build", build_dir, "--parallel"])
+
+        return os.path.join(self._project_root(), build_dir, binary_name)

docs/glossary.md

@@ -1,36 +1,56 @@
 # Glossary
 
-## AssetRegistry
+## ResourceRegistry
 
-An AssetRegistry owns GPU-backed assets on the caller's behalf and hands out
+A ResourceRegistry owns GPU-backed resources on the caller's behalf and hands out
-lightweight Handles instead of pointers or ownership.
+lightweight Handles instead of pointers or ownership. It is engine-internal:
+frontend code never sees it, and reaches it through a ResourceRegistryRef.
 
-Internally it's a collection of per-type pools, each responsible for one
+Internally it's a collection of per-type pools, each a `Pool<T, Handle>`
-asset type:
+(a generation-checked slot pool). A type that needs extra behaviour wraps its
+pool in a thin class instead:
 
 ```
-AssetRegistry
+ResourceRegistry
- ├── MeshPool     → MeshHandle
+ ├── meshPool          Pool<Mesh, MeshHandle>
- ├── TexturePool  → TextureHandle   (planned)
+ ├── renderTargetPool  RenderTargetPool → RenderTargetHandle
- └── MaterialPool → MaterialHandle  (planned)
+ │                     (wraps Pool; waits for the GPU on release, applies resizes)
+ ├── texturePool       (planned)
+ └── materialPool      (planned)
 ```
 
+Engine code (`Application`, `ImGuiRenderer`, `SceneRenderer`) uses the pools
+directly, e.g. `resources.renderTargetPool.get(handle)`.
+
 A Handle is a small (index, generation) pair. The index locates the slot in
 the pool; the generation is bumped when that slot is released, so a Handle
 kept around after release() is detected as stale instead of resolving to
-someone else's asset (or freed memory).
+someone else's resource (or freed memory).
+
+Think: "Where does the engine keep every GPU resource, and how does it look one
+up by handle?"
+
+## ResourceRegistryRef
+
+A ResourceRegistryRef is the frontend's non-owning, cheap-to-copy view of the
+ResourceRegistry, returned by `Application::resources()`. It exposes only what
+frontend code needs and hands out no pools, so no Vulkan-facing types leak
+through the public API:
+
+```
+create<T>(...)   load<T>(path)   release<T>(handle)
+requestResize(target, w, h)   getExtent(target)   isAlive(handle)
+```
 
 Typical lifecycle:
 
 ```
-load<Mesh>(path) / loadMesh(...)  →  MeshHandle
+load<Mesh>(path) / create<Mesh>(...)  →  MeshHandle
-                                        │
-                        get<Mesh>(handle)  →  const Mesh&
                                         │
                         release<Mesh>(handle)
 ```
 
-Think: "Where do I get or release a GPU asset by handle, without owning its
+Think: "How do I create or release a GPU resource by handle, without owning its
 lifetime directly?"
 
 ## Buffer
@@ -256,12 +276,14 @@ This is primarily a UI concept, rather than a GPU concept.
 A PanelRegistry owns Panels on the caller's behalf and hands out lightweight
 PanelHandles instead of pointers or ownership.
 
-Internally it's a generation-checked slot pool, the same shape AssetRegistry's
+Internally it wraps a `Pool<Panel, PanelHandle>` (the same generation-checked
-per-type pools use:
+slot pool ResourceRegistry uses, in `sophia/util/pool.hpp`) and adds the
+Panel-specific parts: lookup by type or name, and the default dock layout:
 
 ```
 PanelRegistry
- └── Slot { Panel, generation }  →  PanelHandle
+ └── Pool<Panel, PanelHandle>
+      └── Slot { Panel, generation }  →  PanelHandle
 ```
 
 Typical lifecycle:
@@ -279,6 +301,34 @@ Each frame, update(frameInfo) calls onUpdate on every visible Panel it holds.
 Think: "Where do I register or look up a UI panel by handle, without owning
 its lifetime directly?"
 
+## SceneRegistry
+
+A SceneRegistry owns Scenes on the caller's behalf and hands out lightweight
+SceneHandles instead of pointers or ownership. Like PanelRegistry, it is owned
+by Application and reached from frontend code directly (`scenes()`), rather than
+through ResourceRegistryRef: scenes are CPU-side entity data, not GPU resources.
+
+Internally it wraps a `Pool<Scene, SceneHandle>`:
+
+```
+SceneRegistry
+ └── Pool<Scene, SceneHandle>
+      └── Slot { Scene, generation }  →  SceneHandle
+```
+
+Typical lifecycle:
+
+```
+create()  →  SceneHandle
+                  │
+        get(handle)  →  Scene&
+                  │
+        release(handle)
+```
+
+Think: "Where do I create or look up a Scene by handle, without owning its
+lifetime directly?"
+
 ## Sprite
 
 A Sprite is a 2D renderable representation of an image, usually a rectangular region of a texture.

editor/CMakeLists.txt

@@ -0,0 +1,27 @@
+set(NAME editor)
+set(ENGINE_NAME ${PROJECT_NAME})
+
+file(GLOB_RECURSE SOURCES CONFIGURE_DEPENDS *.cpp src/*.cpp)
+
+add_library(${NAME}_deps INTERFACE)
+
+target_link_libraries(${NAME}_deps INTERFACE
+  ${ENGINE_NAME}
+  imguizmo
+)
+
+target_compile_features(${PROJECT_NAME} PUBLIC cxx_std_23)
+set_property(TARGET ${PROJECT_NAME} PROPERTY VS_DEBUGGER_WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}/build")
+
+add_executable(editor ${SOURCES})
+
+target_link_libraries(editor PRIVATE ${NAME}_deps)
+
+target_include_directories(editor PRIVATE
+    "${CMAKE_SOURCE_DIR}/engine/include"
+    "${CMAKE_SOURCE_DIR}/external/imgui"
+)
+
+target_compile_definitions(editor PRIVATE
+  EDITOR_SHADER_DIR="${CMAKE_CURRENT_SOURCE_DIR}/shaders"
+)

editor/editor_camera.cpp

@@ -0,0 +1,99 @@
+#include "editor_camera.hpp"
+
+#include <algorithm>
+#include <cmath>
+
+namespace {
+
+constexpr float ORBIT_RADIANS_PER_PIXEL = 0.005f;
+const float MAX_PITCH = glm::radians(89.f);
+// Each wheel step moves this fraction of the way towards the pivot.
+constexpr float ZOOM_STEP = 0.1f;
+constexpr float MIN_DISTANCE = 0.05f;
+constexpr float MIN_ORTHO_HEIGHT = 0.01f;
+// Fly speed per unit of distance from the pivot, so it suits any scale.
+constexpr float FLY_SPEED = 1.5f;
+
+}  // namespace
+
+void EditorCamera::orbit(glm::vec2 pixels) {
+  if (mode != Mode::Scene3D) {
+    return;
+  }
+  yaw -= pixels.x * ORBIT_RADIANS_PER_PIXEL;
+  pitch = std::clamp(pitch - pixels.y * ORBIT_RADIANS_PER_PIXEL, -MAX_PITCH,
+                     MAX_PITCH);
+}
+
+void EditorCamera::pan(glm::vec2 pixels, float viewportHeight) {
+  if (viewportHeight <= 0.f) {
+    return;
+  }
+
+  // World units one pixel covers at the pivot's depth.
+  float unitsPerPixel =
+      mode == Mode::Scene3D
+          ? 2.f * distance * std::tan(fov / 2.f) / viewportHeight
+          : orthoHeight / viewportHeight;
+
+  // Screen y runs down, world y up. Dragging moves the scene with the mouse,
+  // so the camera moves the other way.
+  glm::vec3 offset{-pixels.x * unitsPerPixel, pixels.y * unitsPerPixel, 0.f};
+  pivot += mode == Mode::Scene3D ? getRotation() * offset : offset;
+}
+
+void EditorCamera::zoom(float steps) {
+  float scale = std::pow(1.f - ZOOM_STEP, steps);
+  if (mode == Mode::Scene3D) {
+    distance = std::max(distance * scale, MIN_DISTANCE);
+  } else {
+    orthoHeight = std::max(orthoHeight * scale, MIN_ORTHO_HEIGHT);
+  }
+}
+
+void EditorCamera::fly(glm::vec3 direction, float deltaTime) {
+  if (mode != Mode::Scene3D || direction == glm::vec3{0.f}) {
+    return;
+  }
+  float speed = FLY_SPEED * std::max(distance, 1.f);
+  pivot += getRotation() * glm::normalize(direction) * speed * deltaTime;
+}
+
+void EditorCamera::frame(glm::vec3 target, float radius) {
+  pivot = target;
+  radius = std::max(radius, 0.1f);
+  // Far enough that the sphere fits in the vertical field of view.
+  distance = radius / std::sin(fov / 2.f);
+  orthoHeight = radius * 2.5f;
+}
+
+sophia::TransformComponent EditorCamera::getTransform() const {
+  sophia::TransformComponent transform;
+  if (mode == Mode::Scene3D) {
+    transform.rotation = getRotation();
+    transform.position =
+        pivot + transform.rotation * glm::vec3{0.f, 0.f, distance};
+  } else {
+    transform.position = pivot;
+  }
+  return transform;
+}
+
+sophia::CameraComponent EditorCamera::getCamera() const {
+  sophia::CameraComponent camera;
+  if (mode == Mode::Scene3D) {
+    camera.projection = sophia::CameraComponent::Projection::Perspective;
+    camera.perspective.fov = fov;
+    // Room to zoom far out without the scene clipping.
+    camera.perspective.farPlane = 1000.f;
+  } else {
+    camera.projection = sophia::CameraComponent::Projection::Orthographic;
+    camera.ortho.height = orthoHeight;
+  }
+  return camera;
+}
+
+glm::quat EditorCamera::getRotation() const {
+  return glm::angleAxis(yaw, glm::vec3{0.f, 1.f, 0.f}) *
+         glm::angleAxis(pitch, glm::vec3{1.f, 0.f, 0.f});
+}

editor/editor_camera.hpp

@@ -0,0 +1,49 @@
+#pragma once
+
+#include <sophia/components.hpp>
+#include <sophia/math.hpp>
+
+/**
+ * The Scene panel's camera. Not part of any scene the editor edits, and never
+ * saved with one.
+ *
+ * In 3D it orbits a pivot point at some distance; in 2D it looks straight
+ * down -Z at the pivot through an orthographic projection, like a 2D game
+ * camera.
+ */
+class EditorCamera {
+ public:
+  enum class Mode { Scene3D, Scene2D };
+
+  Mode mode = Mode::Scene3D;
+
+  // Turns around the pivot by a mouse movement in pixels. 3D only.
+  void orbit(glm::vec2 pixels);
+  // Moves the pivot so the scene follows a mouse movement in pixels across a
+  // viewport `viewportHeight` pixels tall.
+  void pan(glm::vec2 pixels, float viewportHeight);
+  // Moves in (positive) or out by mouse wheel steps.
+  void zoom(float steps);
+  // Moves the pivot along the camera's axes: x right, y up, z backwards.
+  // `direction` needn't be normalized. 3D only.
+  void fly(glm::vec3 direction, float deltaTime);
+  // Centers on `target`, backing off enough to see a sphere of `radius`.
+  void frame(glm::vec3 target, float radius);
+
+  sophia::TransformComponent getTransform() const;
+  sophia::CameraComponent getCamera() const;
+
+ private:
+  glm::quat getRotation() const;
+
+  glm::vec3 pivot{0.f, 0.f, 0.f};
+
+  // 3D: looking at the pivot from in front, a little to the right and above.
+  float yaw = glm::radians(30.f);
+  float pitch = glm::radians(-25.f);
+  float distance = 8.f;
+  float fov = glm::radians(60.f);
+
+  // 2D: world units visible from the bottom of the view to the top.
+  float orthoHeight = 10.f;
+};

editor/editor_context.hpp

@@ -0,0 +1,89 @@
+#pragma once
+
+#include <sophia/entity.hpp>
+#include <sophia/handles.hpp>
+#include <sophia/scene.hpp>
+#include <sophia/scene_registry.hpp>
+#include <sophia/scene_view_registry.hpp>
+#include <string>
+#include <vector>
+
+/**
+ * What the editor is working on, shared by its panels. Panels read it every
+ * frame instead of holding on to a scene, so switching scenes is one call.
+ */
+class EditorContext {
+ public:
+  // A scene the editor has open, and can switch to.
+  struct OpenScene {
+    sophia::SceneHandle handle;
+    std::string name;
+  };
+
+  explicit EditorContext(sophia::SceneRegistry& scenes) : scenes{scenes} {}
+
+  // Creates an open scene with a "Main Camera", without switching to it.
+  sophia::SceneHandle createScene(std::string name) {
+    sophia::SceneHandle handle = scenes.create();
+    scenes.get(handle).createCamera("Main Camera");
+    openScenes.push_back({handle, std::move(name)});
+    return handle;
+  }
+
+  const std::vector<OpenScene>& getOpenScenes() const { return openScenes; }
+
+  // Null if `handle` isn't an open scene.
+  const std::string* getSceneName(sophia::SceneHandle handle) const {
+    for (const OpenScene& open : openScenes) {
+      if (open.handle == handle) {
+        return &open.name;
+      }
+    }
+    return nullptr;
+  }
+
+  void renameScene(sophia::SceneHandle handle, std::string name) {
+    for (OpenScene& open : openScenes) {
+      if (open.handle == handle) {
+        open.name = std::move(name);
+      }
+    }
+  }
+
+  bool hasScene() const { return scenes.isAlive(activeScene); }
+  sophia::SceneHandle getSceneHandle() const { return activeScene; }
+  sophia::Scene& getScene() { return scenes.get(activeScene); }
+
+  // Also clears the selection, which belonged to the previous scene.
+  void setScene(sophia::SceneHandle handle) {
+    activeScene = handle;
+    selected = {};
+  }
+
+  // Null when nothing is selected. Always an entity of the active scene.
+  sophia::Entity selected;
+
+ private:
+  sophia::SceneRegistry& scenes;
+  sophia::SceneHandle activeScene = sophia::INVALID_HANDLE;
+  // Kept open even when not active: with no saving yet, closing one would
+  // lose it.
+  std::vector<OpenScene> openScenes;
+};
+
+// Points `view` at the context's active scene, and renders it only while
+// there is one and its panel is `shown`. Call every frame from the panel that
+// owns the view.
+inline void syncSceneView(EditorContext& context,
+                          sophia::SceneViewRegistry& sceneViews,
+                          sophia::SceneViewHandle view, bool shown) {
+  bool enabled = shown && context.hasScene();
+  const sophia::SceneView& current = sceneViews.peek(view);
+  // get() re-sorts the render queue, so only use it when something changed.
+  if (current.enabled != enabled ||
+      (context.hasScene() && current.scene != context.getSceneHandle())) {
+    sophia::SceneView& updated = sceneViews.get(view);
+    updated.enabled = enabled;
+    updated.scene = context.getSceneHandle();
+  }
+}

editor/main.cpp

@@ -0,0 +1,153 @@
+#include <sophia/application.hpp>
+#include <sophia/components.hpp>
+#include <sophia/entity.hpp>
+#include <sophia/primitives.hpp>
+#include <vector>
+
+#include "editor_context.hpp"
+#include "panels/asset_browser_panel.hpp"
+#include "panels/game_panel.hpp"
+#include "panels/inspector_panel.hpp"
+#include "panels/scene_hierarchy_panel.hpp"
+#include "panels/scene_panel.hpp"
+#include "utilities/logger.hpp"
+
+class Editor : public sophia::Application {
+ public:
+  Editor() : Application{{.width = 750, .height = 1000, .name = "Editor"}} {}
+
+  void onCreate() override {
+    log("Editor created");
+
+    debugUI().show();
+
+    textures.emplace_back("Checker", createCheckerTexture());
+    cubeMesh = createShadedCube();
+
+    sophia::SceneHandle sceneHandle = context.createScene("Demo");
+    createDemoScene(scenes().get(sceneHandle));
+    context.setScene(sceneHandle);
+
+    // The editor's own scene, never edited or rendered. It holds the camera
+    // the Scene panel looks through, which a SceneView may take from any
+    // scene.
+    sophia::SceneHandle editorSceneHandle = scenes().create();
+    sophia::Entity editorCamera =
+        scenes().get(editorSceneHandle).createCamera("Editor Camera");
+
+    // Views start without a scene; their panels point them at the active
+    // scene each frame.
+    sophia::RenderTargetHandle sceneTarget =
+        resources().create<sophia::RenderTarget>();
+    sophia::SceneViewHandle sceneView = sceneViews().create(
+        {.target = sceneTarget, .camera = editorCamera, .enabled = false});
+
+    // No camera: the Game panel shows the scene through its active one.
+    sophia::RenderTargetHandle gameTarget =
+        resources().create<sophia::RenderTarget>();
+    sophia::SceneViewHandle gameView =
+        sceneViews().create({.target = gameTarget, .enabled = false});
+
+    panels().emplace<SceneHierarchyPanel>(context, cubeMesh);
+    panels().emplace<InspectorPanel>(context, textures);
+    panels().emplace<AssetBrowserPanel>();
+    viewPanels.push_back(
+        {panels().emplace<ScenePanel>(ui(), resources(), context, sceneViews(),
+                                      sceneView, sceneTarget, editorCamera),
+         sceneView});
+    viewPanels.push_back(
+        {panels().emplace<GamePanel>(ui(), context, sceneViews(), gameView,
+                                     gameTarget),
+         gameView});
+
+    panels().setDefaultLayout(
+        {.left = {"Scene Hierarchy"},
+         .right = {"Inspector", "Frame Stats", "PanelRegistry"},
+         .bottom = {"Asset Browser", "Console"},
+         .center = {"Scene", "Game"}});
+  }
+
+  void onUpdate(const sophia::FrameInfo& frameInfo) override {
+    // A closed panel's onUpdate() doesn't run, so it can't stop its view
+    // rendering itself.
+    for (const ViewPanel& viewPanel : viewPanels) {
+      if (!panels().get(viewPanel.panel).isVisible() &&
+          sceneViews().peek(viewPanel.view).enabled) {
+        sceneViews().get(viewPanel.view).enabled = false;
+      }
+    }
+  }
+
+ private:
+  // Adds to a new scene, which already has a camera.
+  void createDemoScene(sophia::Scene& scene) {
+    sophia::Entity checker = scene.createEntity("Checker");
+    checker.getComponent<sophia::TransformComponent>().position = {-1.5f, 0.f,
+                                                                   0.f};
+    checker.addComponent<sophia::SpriteComponent>(sophia::SpriteComponent{
+        .texture = textures[0].second, .size = {2.f, 2.f}});
+
+    sophia::Entity red = scene.createEntity("Red");
+    red.getComponent<sophia::TransformComponent>().position = {1.f, -0.5f, 0.f};
+    red.addComponent<sophia::SpriteComponent>(sophia::SpriteComponent{
+        .color = {0.9f, 0.25f, 0.25f, 1.f}, .size = {2.f, 2.f}});
+
+    // Drawn over "Red" because of its higher sort order.
+    sophia::Entity blue = scene.createEntity("Blue (translucent)");
+    blue.getComponent<sophia::TransformComponent>().position = {1.75f, 0.25f,
+                                                                0.f};
+    blue.addComponent<sophia::SpriteComponent>(
+        sophia::SpriteComponent{.color = {0.25f, 0.45f, 0.95f, 0.6f},
+                                .size = {2.f, 2.f},
+                                .sortOrder = 1});
+
+    sophia::Entity cube = scene.createEntity("Cube");
+    auto& cubeTransform = cube.getComponent<sophia::TransformComponent>();
+    cubeTransform.position = {0.f, 2.5f, 0.f};
+    cubeTransform.rotation =
+        glm::quat{glm::radians(glm::vec3{30.f, 45.f, 0.f})};
+    cube.addComponent<sophia::MeshComponent>(sophia::MeshComponent{
+        .handle = cubeMesh, .color = {0.4f, 0.8f, 0.5f, 1.f}});
+  }
+
+  // Meshes are unlit, so a plain cube is a flat silhouette. Bake a fixed
+  // light into its vertex colors so its faces read in 3D until there's real
+  // lighting; MeshComponent::color still tints it.
+  sophia::MeshHandle createShadedCube() {
+    const glm::vec3 lightDirection = glm::normalize(glm::vec3{0.4f, 1.f, 0.7f});
+    sophia::MeshData data = sophia::primitives::cube();
+    for (sophia::MeshVertex& vertex : data.vertices) {
+      float light = glm::dot(vertex.normal, lightDirection) * 0.5f + 0.5f;
+      vertex.color = glm::vec4{glm::vec3{0.35f + 0.65f * light}, 1.f};
+    }
+    return resources().create<sophia::Mesh>(data);
+  }
+
+  sophia::TextureHandle createCheckerTexture() {
+    constexpr sophia::u32 SIZE = 8;
+    std::vector<sophia::u8> pixels(SIZE * SIZE * 4);
+    for (sophia::u32 y = 0; y < SIZE; y++) {
+      for (sophia::u32 x = 0; x < SIZE; x++) {
+        sophia::u8 value = ((x + y) % 2 == 0) ? 230 : 60;
+        sophia::u8* pixel = &pixels[(y * SIZE + x) * 4];
+        pixel[0] = pixel[1] = pixel[2] = value;
+        pixel[3] = 255;
+      }
+    }
+    return resources().create<sophia::Texture>(SIZE, SIZE, std::move(pixels));
+  }
+
+  // A panel showing a scene view, which should only render while the panel
+  // is on screen.
+  struct ViewPanel {
+    sophia::PanelHandle panel;
+    sophia::SceneViewHandle view;
+  };
+
+  EditorContext context{scenes()};
+  std::vector<ViewPanel> viewPanels;
+  InspectorPanel::TextureList textures;
+  sophia::MeshHandle cubeMesh;
+};
+
+SOPHIA_MAIN(Editor)

editor/panels/asset_browser_panel.cpp

@@ -0,0 +1,23 @@
+#include "asset_browser_panel.hpp"
+
+#include <imgui.h>
+
+void AssetBrowserPanel::onUpdate(const sophia::FrameInfo&) {
+  ImGui::BeginChild("Folders", ImVec2(150, 0), true);
+  for (int i = 0; i < static_cast<int>(folders.size()); i++) {
+    if (ImGui::Selectable(folders[static_cast<size_t>(i)].name.c_str(),
+                          selectedFolder == i)) {
+      selectedFolder = i;
+    }
+  }
+  ImGui::EndChild();
+
+  ImGui::SameLine();
+
+  ImGui::BeginChild("Files", ImVec2(0, 0), true);
+  const Folder& folder = folders[static_cast<size_t>(selectedFolder)];
+  for (const std::string& file : folder.files) {
+    ImGui::Selectable(file.c_str());
+  }
+  ImGui::EndChild();
+}

editor/panels/asset_browser_panel.hpp

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <sophia/frame_info.hpp>
+#include <sophia/ui/panel.hpp>
+#include <string>
+#include <vector>
+
+class AssetBrowserPanel : public sophia::Panel {
+ public:
+  AssetBrowserPanel() : Panel{{.name = "Asset Browser"}} {}
+
+  void onUpdate(const sophia::FrameInfo& frameInfo) override;
+
+ private:
+  struct Folder {
+    std::string name;
+    std::vector<std::string> files;
+  };
+
+  std::vector<Folder> folders = {
+      {"Models", {"player_capsule.fbx", "ground_plane.fbx", "enemy_grunt.fbx"}},
+      {"Textures",
+       {"brick_diffuse.png", "grass_albedo.png", "player_diffuse.png"}},
+      {"Materials", {"player_mat.mat", "ground_mat.mat"}},
+      {"Scripts", {"PlayerController.lua", "EnemyAI.lua"}},
+      {"Scenes", {"MainMenu.scene", "Level_01.scene"}},
+  };
+
+  int selectedFolder = 0;
+};

editor/panels/game_panel.cpp

@@ -0,0 +1,20 @@
+#include "game_panel.hpp"
+
+#include <imgui.h>
+
+void GamePanel::onUpdate(const sophia::FrameInfo&) {
+  syncSceneView(context, sceneViews, view, isShown());
+
+  if (!context.hasScene()) {
+    ImGui::TextDisabled("No scene open");
+    return;
+  }
+
+  const ImVec2 origin = ImGui::GetCursorScreenPos();
+  ui.image(target);
+
+  if (!context.getScene().getActiveCamera()) {
+    ImGui::SetCursorScreenPos(ImVec2(origin.x + 8.0f, origin.y + 8.0f));
+    ImGui::TextDisabled("The scene has no active camera");
+  }
+}

editor/panels/game_panel.hpp

@@ -0,0 +1,39 @@
+#pragma once
+
+#include <sophia/frame_info.hpp>
+#include <sophia/handles.hpp>
+#include <sophia/scene_view_registry.hpp>
+#include <sophia/ui/panel.hpp>
+#include <sophia/ui/ui.hpp>
+
+#include "../editor_context.hpp"
+
+/**
+ * Shows the active scene through its own active camera: what the game will
+ * see.
+ */
+class GamePanel : public sophia::Panel {
+ public:
+  // Renders into `target` through `view`, a SceneView with no camera of its
+  // own that this panel keeps pointed at the active scene.
+  GamePanel(sophia::UI& ui, EditorContext& context,
+            sophia::SceneViewRegistry& sceneViews, sophia::SceneViewHandle view,
+            sophia::RenderTargetHandle target)
+      : Panel{{.name = "Game",
+               .windowFlags = ImGuiWindowFlags_NoScrollbar |
+                              ImGuiWindowFlags_NoScrollWithMouse}},
+        ui{ui},
+        context{context},
+        sceneViews{sceneViews},
+        view{view},
+        target{target} {}
+
+  void onUpdate(const sophia::FrameInfo& frameInfo) override;
+
+ private:
+  sophia::UI& ui;
+  EditorContext& context;
+  sophia::SceneViewRegistry& sceneViews;
+  sophia::SceneViewHandle view;
+  sophia::RenderTargetHandle target;
+};

editor/panels/inspector_panel.cpp

@@ -0,0 +1,164 @@
+#include "inspector_panel.hpp"
+
+#include <imgui.h>
+
+#include <cstdio>
+#include <sophia/components.hpp>
+
+void InspectorPanel::onUpdate(const sophia::FrameInfo&) {
+  selected = context.selected;
+  if (!selected) {
+    ImGui::TextDisabled("No entity selected");
+    return;
+  }
+
+  drawTag();
+  ImGui::Separator();
+  drawTransform();
+  drawCamera();
+  drawSprite();
+  drawMesh();
+
+  ImGui::Separator();
+  drawAddComponent();
+}
+
+void InspectorPanel::drawTag() {
+  auto& tag = selected.getComponent<sophia::TagComponent>();
+
+  char nameBuf[128];
+  std::snprintf(nameBuf, sizeof(nameBuf), "%s", tag.tag.c_str());
+  if (ImGui::InputText("Name", nameBuf, sizeof(nameBuf))) {
+    tag.tag = nameBuf;
+  }
+}
+
+void InspectorPanel::drawTransform() {
+  if (!selected.hasComponent<sophia::TransformComponent>() ||
+      !ImGui::CollapsingHeader("Transform", ImGuiTreeNodeFlags_DefaultOpen)) {
+    return;
+  }
+
+  auto& transform = selected.getComponent<sophia::TransformComponent>();
+  ImGui::DragFloat3("Position", &transform.position.x, 0.1f);
+
+  // Euler angles in degrees, recomputed from the quaternion every frame.
+  // Near 90 degrees of pitch the angles can jump between equivalent values
+  // while dragging.
+  // TODO: keep each entity's edited angles, or replace with gizmo rotation.
+  glm::vec3 degrees = glm::degrees(glm::eulerAngles(transform.rotation));
+  if (ImGui::DragFloat3("Rotation", &degrees.x, 1.0f)) {
+    transform.rotation = glm::quat{glm::radians(degrees)};
+  }
+
+  ImGui::DragFloat3("Scale", &transform.scale.x, 0.1f);
+}
+
+void InspectorPanel::drawCamera() {
+  if (!selected.hasComponent<sophia::CameraComponent>() ||
+      !ImGui::CollapsingHeader("Camera", ImGuiTreeNodeFlags_DefaultOpen)) {
+    return;
+  }
+
+  auto& camera = selected.getComponent<sophia::CameraComponent>();
+  int projection = static_cast<int>(camera.projection);
+  if (ImGui::Combo("Projection", &projection, "Orthographic\0Perspective\0")) {
+    camera.projection =
+        static_cast<sophia::CameraComponent::Projection>(projection);
+  }
+
+  if (camera.projection == sophia::CameraComponent::Projection::Orthographic) {
+    ImGui::DragFloat("Height", &camera.ortho.height, 0.1f, 0.01f, 10000.f);
+  } else {
+    float fov = glm::degrees(camera.perspective.fov);
+    if (ImGui::DragFloat("FOV", &fov, 0.5f, 1.f, 179.f)) {
+      camera.perspective.fov = glm::radians(fov);
+    }
+  }
+}
+
+void InspectorPanel::drawSprite() {
+  if (!selected.hasComponent<sophia::SpriteComponent>()) {
+    return;
+  }
+
+  bool open = true;
+  if (!ImGui::CollapsingHeader("Sprite", &open,
+                               ImGuiTreeNodeFlags_DefaultOpen)) {
+    if (!open) {
+      selected.removeComponent<sophia::SpriteComponent>();
+    }
+    return;
+  }
+
+  auto& sprite = selected.getComponent<sophia::SpriteComponent>();
+
+  const char* current = "None";
+  for (const auto& [name, handle] : textures) {
+    if (handle == sprite.texture) {
+      current = name.c_str();
+    }
+  }
+  if (ImGui::BeginCombo("Texture", current)) {
+    if (ImGui::Selectable("None", !sprite.texture.isValid())) {
+      sprite.texture = sophia::INVALID_HANDLE;
+    }
+    for (const auto& [name, handle] : textures) {
+      if (ImGui::Selectable(name.c_str(), handle == sprite.texture)) {
+        sprite.texture = handle;
+      }
+    }
+    ImGui::EndCombo();
+  }
+
+  ImGui::ColorEdit4("Color", &sprite.color.x);
+  ImGui::DragFloat2("Size", &sprite.size.x, 0.05f);
+  ImGui::SliderFloat2("Pivot", &sprite.pivot.x, 0.f, 1.f);
+  ImGui::DragFloat4("UV Rect", &sprite.uvRect.x, 0.01f);
+  ImGui::DragInt("Sort Order", &sprite.sortOrder);
+
+  if (!open) {
+    selected.removeComponent<sophia::SpriteComponent>();
+  }
+}
+
+void InspectorPanel::drawMesh() {
+  if (!selected.hasComponent<sophia::MeshComponent>()) {
+    return;
+  }
+
+  bool open = true;
+  if (!ImGui::CollapsingHeader("Mesh", &open, ImGuiTreeNodeFlags_DefaultOpen)) {
+    if (!open) {
+      selected.removeComponent<sophia::MeshComponent>();
+    }
+    return;
+  }
+
+  auto& mesh = selected.getComponent<sophia::MeshComponent>();
+  // TODO: pick the mesh once assets have names.
+  ImGui::Text("Mesh: %u", static_cast<sophia::u32>(mesh.handle.index));
+  ImGui::ColorEdit3("Color", &mesh.color.x);
+
+  if (!open) {
+    selected.removeComponent<sophia::MeshComponent>();
+  }
+}
+
+void InspectorPanel::drawAddComponent() {
+  if (ImGui::Button("Add Component")) {
+    ImGui::OpenPopup("AddComponent");
+  }
+
+  if (ImGui::BeginPopup("AddComponent")) {
+    if (!selected.hasComponent<sophia::SpriteComponent>() &&
+        ImGui::MenuItem("Sprite")) {
+      selected.addComponent<sophia::SpriteComponent>();
+    }
+    if (!selected.hasComponent<sophia::CameraComponent>() &&
+        ImGui::MenuItem("Camera")) {
+      selected.addComponent<sophia::CameraComponent>();
+    }
+    ImGui::EndPopup();
+  }
+}

editor/panels/inspector_panel.hpp

@@ -0,0 +1,36 @@
+#pragma once
+
+#include <sophia/entity.hpp>
+#include <sophia/frame_info.hpp>
+#include <sophia/handles.hpp>
+#include <sophia/ui/panel.hpp>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "../editor_context.hpp"
+
+class InspectorPanel : public sophia::Panel {
+ public:
+  // Stand-in for an asset browser: the textures a sprite can pick from.
+  using TextureList =
+      std::vector<std::pair<std::string, sophia::TextureHandle>>;
+
+  InspectorPanel(EditorContext& context, const TextureList& textures)
+      : Panel{{.name = "Inspector"}}, context{context}, textures{textures} {}
+
+  void onUpdate(const sophia::FrameInfo& frameInfo) override;
+
+ private:
+  void drawTag();
+  void drawTransform();
+  void drawCamera();
+  void drawSprite();
+  void drawMesh();
+  void drawAddComponent();
+
+  EditorContext& context;
+  // The selected entity, for the duration of onUpdate().
+  sophia::Entity selected;
+  const TextureList& textures;
+};

editor/panels/scene_hierarchy_panel.cpp

@@ -0,0 +1,134 @@
+#include "scene_hierarchy_panel.hpp"
+
+#include <imgui.h>
+
+#include <cstdio>
+#include <sophia/components.hpp>
+#include <string>
+
+void SceneHierarchyPanel::onUpdate(const sophia::FrameInfo&) {
+  drawSceneSelector();
+  ImGui::Separator();
+
+  if (!context.hasScene()) {
+    ImGui::TextDisabled("No scene open");
+    return;
+  }
+
+  sophia::Scene& scene = context.getScene();
+  sophia::Entity& selected = context.selected;
+
+  if (ImGui::Button("+ Sprite")) {
+    selected = scene.createEntity("Sprite");
+    selected.addComponent<sophia::SpriteComponent>();
+  }
+  ImGui::SameLine();
+  if (ImGui::Button("+ Cube")) {
+    selected = scene.createEntity("Cube");
+    selected.addComponent<sophia::MeshComponent>(
+        sophia::MeshComponent{.handle = cubeMesh});
+  }
+
+  ImGui::Separator();
+
+  // Flat for now: there is no parent/child component yet.
+  scene.forEachEntity([&selected](sophia::Entity entity) {
+    ImGuiTreeNodeFlags flags = ImGuiTreeNodeFlags_Leaf |
+                               ImGuiTreeNodeFlags_NoTreePushOnOpen |
+                               ImGuiTreeNodeFlags_SpanAvailWidth;
+    if (entity == selected) {
+      flags |= ImGuiTreeNodeFlags_Selected;
+    }
+
+    const std::string& name = entity.getComponent<sophia::TagComponent>().tag;
+    ImGui::PushID(static_cast<int>(static_cast<sophia::u32>(entity)));
+    ImGui::TreeNodeEx(name.c_str(), flags);
+    if (ImGui::IsItemClicked()) {
+      selected = entity;
+    }
+    ImGui::PopID();
+  });
+}
+
+namespace {
+// See SceneHierarchyPanel::renameFocusFrames.
+constexpr int RENAME_FOCUS_FRAMES = 2;
+}  // namespace
+
+void SceneHierarchyPanel::drawSceneSelector() {
+  // Leave room for the button: its label, its padding, and the gap to it.
+  constexpr const char* ADD_SCENE_LABEL = "Add Scene";
+  const ImGuiStyle& style = ImGui::GetStyle();
+  ImGui::SetNextItemWidth(-(ImGui::CalcTextSize(ADD_SCENE_LABEL).x +
+                            style.FramePadding.x * 2.f + style.ItemSpacing.x));
+
+  const std::string* current = context.getSceneName(context.getSceneHandle());
+  bool startRename = false;
+
+  if (renamingScene && current) {
+    drawSceneRename();
+  } else {
+    renamingScene = false;
+    if (ImGui::BeginCombo("##scene", current ? current->c_str() : "No scene")) {
+      for (const EditorContext::OpenScene& open : context.getOpenScenes()) {
+        ImGui::PushID(static_cast<int>(open.handle.index));
+        bool isCurrent = open.handle == context.getSceneHandle();
+        if (ImGui::Selectable(open.name.c_str(), isCurrent) && !isCurrent) {
+          context.setScene(open.handle);
+        }
+        ImGui::PopID();
+      }
+      ImGui::EndCombo();
+    }
+
+    if (current && ImGui::BeginPopupContextItem("##sceneMenu")) {
+      startRename = ImGui::MenuItem("Rename", "F2");
+      ImGui::EndPopup();
+    }
+    startRename = startRename || (current && ImGui::IsWindowFocused() &&
+                                  !ImGui::GetIO().WantTextInput &&
+                                  ImGui::IsKeyPressed(ImGuiKey_F2));
+  }
+
+  ImGui::SameLine();
+  if (ImGui::Button(ADD_SCENE_LABEL)) {
+    std::string name = "Untitled " + std::to_string(++this->untitledSceneCount);
+    context.setScene(context.createScene(std::move(name)));
+    startRename = false;
+  }
+
+  if (startRename) {
+    renamingScene = true;
+    renameFocusFrames = RENAME_FOCUS_FRAMES;
+    std::snprintf(renameBuffer.data(), renameBuffer.size(), "%s",
+                  current->c_str());
+  }
+}
+
+void SceneHierarchyPanel::drawSceneRename() {
+  if (renameFocusFrames == RENAME_FOCUS_FRAMES) {
+    ImGui::SetKeyboardFocusHere();
+  }
+
+  ImGui::InputText("##sceneName", renameBuffer.data(), renameBuffer.size(),
+                   ImGuiInputTextFlags_AutoSelectAll);
+
+  bool active = ImGui::IsItemActive();
+  if (active) {
+    renameFocusFrames = 0;
+  } else if (renameFocusFrames > 0) {
+    renameFocusFrames--;
+    return;
+  }
+
+  // Escape reverts the text before deactivating, so committing whatever is
+  // left when the field closes covers Enter, clicking away and Escape alike.
+  if (!active) {
+    std::string name = renameBuffer.data();
+    // Keep the old name rather than leave the scene nameless.
+    if (name.find_first_not_of(' ') != std::string::npos) {
+      context.renameScene(context.getSceneHandle(), std::move(name));
+    }
+    renamingScene = false;
+  }
+}

editor/panels/scene_hierarchy_panel.hpp

@@ -0,0 +1,38 @@
+#pragma once
+
+#include <array>
+#include <sophia/frame_info.hpp>
+#include <sophia/handles.hpp>
+#include <sophia/ui/panel.hpp>
+
+#include "../editor_context.hpp"
+
+class SceneHierarchyPanel : public sophia::Panel {
+ public:
+  // `cubeMesh` is what "+ Cube" gives new entities.
+  SceneHierarchyPanel(EditorContext& context, sophia::MeshHandle cubeMesh)
+      : Panel{{.name = "Scene Hierarchy", .locked = true}},
+        context{context},
+        cubeMesh{cubeMesh} {}
+
+  void onUpdate(const sophia::FrameInfo& frameInfo) override;
+
+ private:
+  // Switches between open scenes, renames the active one, and creates new
+  // ones.
+  void drawSceneSelector();
+  // Replaces the selector with a text field editing the active scene's name.
+  void drawSceneRename();
+
+  EditorContext& context;
+  sophia::MeshHandle cubeMesh;
+  // For naming new scenes "Untitled 1", "Untitled 2", ...
+  int untitledSceneCount = 0;
+
+  // Set while the scene selector is a text field for renaming.
+  bool renamingScene = false;
+  // Frames the text field has left to become active after renaming starts;
+  // focus can take a frame to land. If it never does, renaming ends.
+  int renameFocusFrames = 0;
+  std::array<char, 128> renameBuffer{};
+};

editor/panels/scene_panel.cpp

@@ -0,0 +1,603 @@
+#include "scene_panel.hpp"
+
+#include <imgui.h>
+// After imgui.h, which it relies on.
+#include <ImGuizmo.h>
+
+#include <algorithm>
+#include <array>
+#include <cmath>
+#include <glm/gtc/type_ptr.hpp>
+#include <limits>
+#include <optional>
+#include <sophia/aabb.hpp>
+#include <sophia/components.hpp>
+#include <tuple>
+#include <utility>
+#include <vector>
+
+namespace {
+
+// Corners of the unit quad a SpriteComponent's model matrix maps to world.
+constexpr std::array<glm::vec2, 4> UNIT_QUAD{
+    glm::vec2{0.f, 0.f}, glm::vec2{1.f, 0.f}, glm::vec2{1.f, 1.f},
+    glm::vec2{0.f, 1.f}};
+
+const ImU32 SELECTION_COLOR = IM_COL32(255, 170, 40, 255);
+
+// Holding Ctrl snaps the gizmo to these steps.
+constexpr float TRANSLATE_SNAP = 0.5f;
+constexpr float ROTATE_SNAP_DEGREES = 15.f;
+constexpr float SCALE_SNAP = 0.1f;
+
+// Writes a matrix built from a translation, rotation and scale (no shear)
+// back into `transform`. A mirroring matrix comes back with a negative x
+// scale.
+void decompose(const glm::mat4& matrix, sophia::TransformComponent& transform) {
+  transform.position = glm::vec3{matrix[3]};
+
+  glm::vec3 scale{glm::length(glm::vec3{matrix[0]}),
+                  glm::length(glm::vec3{matrix[1]}),
+                  glm::length(glm::vec3{matrix[2]})};
+  if (glm::determinant(glm::mat3{matrix}) < 0.f) {
+    scale.x = -scale.x;
+  }
+  transform.scale = scale;
+
+  // A zero scale loses the axis, and with it the rotation; keep the old one.
+  if (scale.x == 0.f || scale.y == 0.f || scale.z == 0.f) {
+    return;
+  }
+  glm::mat3 rotation{glm::vec3{matrix[0]} / scale.x,
+                     glm::vec3{matrix[1]} / scale.y,
+                     glm::vec3{matrix[2]} / scale.z};
+  transform.rotation = glm::normalize(glm::quat_cast(rotation));
+}
+
+// How far along a ray (from `origin`, along the normalized `direction`) it
+// enters `bounds` placed by `model`, or null if it misses. A ray starting
+// inside hits at 0.
+std::optional<float> intersectBox(const glm::vec3& origin,
+                                  const glm::vec3& direction,
+                                  const glm::mat4& model,
+                                  const sophia::AABB& bounds) {
+  if (glm::determinant(model) == 0.f) {
+    return std::nullopt;
+  }
+
+  // Test in the box's space, where it's axis-aligned. The direction isn't
+  // renormalized, so distances along it are still world distances.
+  glm::mat4 inverse = glm::inverse(model);
+  glm::vec3 localOrigin = glm::vec3{inverse * glm::vec4{origin, 1.f}};
+  glm::vec3 localDirection = glm::vec3{inverse * glm::vec4{direction, 0.f}};
+
+  float enter = 0.f;
+  float exit = std::numeric_limits<float>::infinity();
+  for (int axis = 0; axis < 3; axis++) {
+    if (std::abs(localDirection[axis]) < 1e-8f) {
+      // Parallel to this pair of faces: hits only if already between them.
+      if (localOrigin[axis] < bounds.min[axis] ||
+          localOrigin[axis] > bounds.max[axis]) {
+        return std::nullopt;
+      }
+      continue;
+    }
+
+    float toMin = (bounds.min[axis] - localOrigin[axis]) / localDirection[axis];
+    float toMax = (bounds.max[axis] - localOrigin[axis]) / localDirection[axis];
+    if (toMin > toMax) {
+      std::swap(toMin, toMax);
+    }
+    enter = std::max(enter, toMin);
+    exit = std::min(exit, toMax);
+    if (enter > exit) {
+      return std::nullopt;
+    }
+  }
+  return enter;
+}
+
+// How far along a ray it hits the unit quad (0, 0)-(1, 1) in the XY plane,
+// placed by `model`, or null if it misses.
+std::optional<float> intersectQuad(const glm::vec3& origin,
+                                   const glm::vec3& direction,
+                                   const glm::mat4& model) {
+  if (glm::determinant(model) == 0.f) {
+    return std::nullopt;
+  }
+
+  glm::mat4 inverse = glm::inverse(model);
+  glm::vec3 localOrigin = glm::vec3{inverse * glm::vec4{origin, 1.f}};
+  glm::vec3 localDirection = glm::vec3{inverse * glm::vec4{direction, 0.f}};
+  // Edge on to the quad.
+  if (std::abs(localDirection.z) < 1e-8f) {
+    return std::nullopt;
+  }
+
+  float distance = -localOrigin.z / localDirection.z;
+  if (distance < 0.f) {
+    return std::nullopt;
+  }
+  glm::vec3 hit = localOrigin + distance * localDirection;
+  if (hit.x < 0.f || hit.x > 1.f || hit.y < 0.f || hit.y > 1.f) {
+    return std::nullopt;
+  }
+  return distance;
+}
+
+}  // namespace
+
+ImVec2 ScenePanel::ViewportTransform::clipToScreen(
+    const glm::vec4& clip) const {
+  glm::vec2 ndc = glm::vec2{clip} / clip.w;
+  // Vulkan NDC has +y pointing down, same as the screen.
+  return {origin.x + (ndc.x * 0.5f + 0.5f) * size.x,
+          origin.y + (ndc.y * 0.5f + 0.5f) * size.y};
+}
+
+std::optional<ImVec2> ScenePanel::ViewportTransform::worldToScreen(
+    const glm::vec3& world) const {
+  glm::vec4 clip = viewProjection * glm::vec4{world, 1.f};
+  if (clip.w <= 0.f) {
+    return std::nullopt;
+  }
+  return clipToScreen(clip);
+}
+
+glm::vec2 ScenePanel::ViewportTransform::screenToWorld(
+    const ImVec2& screen) const {
+  glm::vec2 ndc{(screen.x - origin.x) / size.x * 2.f - 1.f,
+                (screen.y - origin.y) / size.y * 2.f - 1.f};
+  glm::vec4 world = inverseViewProjection * glm::vec4{ndc, 0.f, 1.f};
+  return glm::vec2{world} / world.w;
+}
+
+ScenePanel::Ray ScenePanel::ViewportTransform::screenToRay(
+    const ImVec2& screen) const {
+  glm::vec2 ndc{(screen.x - origin.x) / size.x * 2.f - 1.f,
+                (screen.y - origin.y) / size.y * 2.f - 1.f};
+  // Depth runs 0 at the near plane to 1 at the far one.
+  glm::vec4 nearPoint = inverseViewProjection * glm::vec4{ndc, 0.f, 1.f};
+  glm::vec4 farPoint = inverseViewProjection * glm::vec4{ndc, 1.f, 1.f};
+  glm::vec3 from = glm::vec3{nearPoint} / nearPoint.w;
+  glm::vec3 to = glm::vec3{farPoint} / farPoint.w;
+  return {from, glm::normalize(to - from)};
+}
+
+void ScenePanel::ViewportTransform::drawLine(ImDrawList* drawList,
+                                             const glm::vec3& a,
+                                             const glm::vec3& b, ImU32 color,
+                                             float thickness) const {
+  // Just in front of the camera. Points behind it project mirrored, so the
+  // part of the line there is cut off rather than drawn.
+  constexpr float MIN_W = 1e-4f;
+
+  glm::vec4 clipA = viewProjection * glm::vec4{a, 1.f};
+  glm::vec4 clipB = viewProjection * glm::vec4{b, 1.f};
+  if (clipA.w < MIN_W && clipB.w < MIN_W) {
+    return;
+  }
+  if (clipA.w < MIN_W) {
+    clipA = glm::mix(clipA, clipB, (MIN_W - clipA.w) / (clipB.w - clipA.w));
+  } else if (clipB.w < MIN_W) {
+    clipB = glm::mix(clipB, clipA, (MIN_W - clipB.w) / (clipA.w - clipB.w));
+  }
+  drawList->AddLine(clipToScreen(clipA), clipToScreen(clipB), color, thickness);
+}
+
+void ScenePanel::onUpdate(const sophia::FrameInfo& frameInfo) {
+  syncSceneView(context, sceneViews, view, isShown());
+
+  drawToolbar();
+  ImGui::Separator();
+
+  const ImVec2 origin = ImGui::GetCursorScreenPos();
+  const ImVec2 size = ImGui::GetContentRegionAvail();
+  if (size.x < 1.0f || size.y < 1.0f) {
+    return;
+  }
+
+  if (!context.hasScene()) {
+    ImGui::TextDisabled("No scene open");
+    return;
+  }
+
+  ui.image(target);
+
+  // Rolls over ImGuizmo's "mouse is over a handle" state, so IsOver() below
+  // reports last frame's.
+  ImGuizmo::BeginFrame();
+  // A handle can't be grabbed while any ImGui item is hovered, so while the
+  // mouse is over one, leave out the viewport button, and keep the window
+  // still so dragging the handle doesn't drag it. Unless a camera drag is
+  // already under way: dropping the button would end it.
+  bool overGizmo =
+      (ImGuizmo::IsOver() || ImGuizmo::IsUsing()) && !viewportActive;
+  getConfig().windowFlags =
+      overGizmo ? WINDOW_FLAGS | ImGuiWindowFlags_NoMove : WINDOW_FLAGS;
+
+  // The image doesn't take mouse input, so without this, dragging in it
+  // would drag the window instead.
+  ImGui::SetCursorScreenPos(origin);
+  if (overGizmo) {
+    ImGui::Dummy(size);
+  } else {
+    ImGui::InvisibleButton("##viewport", size,
+                           ImGuiButtonFlags_MouseButtonLeft |
+                               ImGuiButtonFlags_MouseButtonRight |
+                               ImGuiButtonFlags_MouseButtonMiddle);
+  }
+  viewportActive = !overGizmo && ImGui::IsItemActive();
+
+  handleCameraInput(frameInfo, size);
+  handleGizmoHotkeys();
+
+  // Drive the view's camera from the editor camera. The scene view renders
+  // after the panels update, so this frame already uses it.
+  camera.getComponent<sophia::TransformComponent>() =
+      editorCamera.getTransform();
+  camera.getComponent<sophia::CameraComponent>() = editorCamera.getCamera();
+
+  ImDrawList* drawList = ImGui::GetWindowDrawList();
+  drawList->PushClipRect(origin, ImVec2(origin.x + size.x, origin.y + size.y),
+                         true);
+
+  // Screen-space, so it only lines up with anything in 2D.
+  // TODO: a world-space grid on the XZ plane for 3D, once there's debug
+  // drawing in scene views.
+  if (showGrid && editorCamera.mode == EditorCamera::Mode::Scene2D) {
+    drawGrid(origin, size);
+  }
+
+  // Use the panel's size rather than the target's: the target is resized a
+  // frame late, and the mouse is over the panel.
+  float aspect = size.x / size.y;
+  glm::mat4 view = sophia::CameraComponent::getView(
+      camera.getComponent<sophia::TransformComponent>());
+  glm::mat4 viewProjection =
+      camera.getComponent<sophia::CameraComponent>().getProjection(aspect) *
+      view;
+  ViewportTransform viewport{origin, size, viewProjection,
+                             glm::inverse(viewProjection)};
+
+  handleSelectionInput(viewport);
+  drawSelection(viewport);
+
+  ImGuizmo::SetDrawlist();
+  ImGuizmo::SetRect(origin.x, origin.y, size.x, size.y);
+  drawGizmo(view, aspect);
+
+  drawList->PopClipRect();
+
+  ImGui::SetCursorScreenPos(ImVec2(origin.x + 8.0f, origin.y + 8.0f));
+  ImGui::TextDisabled("%.0f x %.0f", size.x, size.y);
+}
+
+void ScenePanel::drawToolbar() {
+  bool is2D = editorCamera.mode == EditorCamera::Mode::Scene2D;
+  if (ImGui::Checkbox("2D", &is2D)) {
+    editorCamera.mode =
+        is2D ? EditorCamera::Mode::Scene2D : EditorCamera::Mode::Scene3D;
+    dragging = false;
+  }
+  ImGui::SameLine();
+  ImGui::BeginDisabled(!is2D);
+  ImGui::Checkbox("Grid", &showGrid);
+  ImGui::EndDisabled();
+
+  ImGui::SameLine();
+  ImGui::TextDisabled("|");
+  ImGui::SameLine();
+  const struct {
+    const char* label;
+    GizmoOperation operation;
+  } operations[] = {{"Move (W)", GizmoOperation::Translate},
+                    {"Rotate (E)", GizmoOperation::Rotate},
+                    {"Scale (R)", GizmoOperation::Scale}};
+  for (const auto& entry : operations) {
+    if (ImGui::RadioButton(entry.label, gizmoOperation == entry.operation)) {
+      gizmoOperation = entry.operation;
+    }
+    ImGui::SameLine();
+  }
+  if (ImGui::Button(gizmoLocal ? "Local" : "World")) {
+    gizmoLocal = !gizmoLocal;
+  }
+}
+
+void ScenePanel::handleGizmoHotkeys() {
+  const ImGuiIO& io = ImGui::GetIO();
+  // W/E/Q fly the camera while the right button is held.
+  if (!ImGui::IsWindowFocused() || io.WantTextInput ||
+      ImGui::IsMouseDown(ImGuiMouseButton_Right)) {
+    return;
+  }
+  if (ImGui::IsKeyPressed(ImGuiKey_W, false)) {
+    gizmoOperation = GizmoOperation::Translate;
+  } else if (ImGui::IsKeyPressed(ImGuiKey_E, false)) {
+    gizmoOperation = GizmoOperation::Rotate;
+  } else if (ImGui::IsKeyPressed(ImGuiKey_R, false)) {
+    gizmoOperation = GizmoOperation::Scale;
+  }
+}
+
+void ScenePanel::drawGizmo(const glm::mat4& view, float aspect) {
+  sophia::Entity selected = context.selected;
+  if (!selected) {
+    return;
+  }
+
+  bool is2D = editorCamera.mode == EditorCamera::Mode::Scene2D;
+
+  // In 2D, only the axes that keep things in the XY plane.
+  ImGuizmo::OPERATION operation{};
+  float snapStep = 0.f;
+  switch (gizmoOperation) {
+    case GizmoOperation::Translate:
+      operation = is2D ? ImGuizmo::TRANSLATE_X | ImGuizmo::TRANSLATE_Y
+                       : ImGuizmo::TRANSLATE;
+      snapStep = TRANSLATE_SNAP;
+      break;
+    case GizmoOperation::Rotate:
+      operation = is2D ? ImGuizmo::ROTATE_Z : ImGuizmo::ROTATE;
+      snapStep = ROTATE_SNAP_DEGREES;
+      break;
+    case GizmoOperation::Scale:
+      operation =
+          is2D ? ImGuizmo::SCALE_X | ImGuizmo::SCALE_Y : ImGuizmo::SCALE;
+      snapStep = SCALE_SNAP;
+      break;
+  }
+  std::array<float, 3> snap{snapStep, snapStep, snapStep};
+  bool snapping = ImGui::GetIO().KeyCtrl;
+
+  // ImGuizmo maps clip space to the screen the OpenGL way, with +y up, so it
+  // needs the projection without the Y flip CameraComponent adds for Vulkan.
+  glm::mat4 projection =
+      camera.getComponent<sophia::CameraComponent>().getProjection(aspect);
+  projection[1][1] *= -1.f;
+
+  auto& transform = selected.getComponent<sophia::TransformComponent>();
+  glm::mat4 model = transform.mat4();
+
+  ImGuizmo::SetOrthographic(is2D);
+  // Per entity, so a drag in progress doesn't carry over to a new selection.
+  ImGuizmo::PushID(static_cast<int>(static_cast<sophia::u32>(selected)));
+  bool changed = ImGuizmo::Manipulate(
+      glm::value_ptr(view), glm::value_ptr(projection), operation,
+      gizmoLocal ? ImGuizmo::LOCAL : ImGuizmo::WORLD, glm::value_ptr(model),
+      nullptr, snapping ? snap.data() : nullptr);
+  ImGuizmo::PopID();
+
+  if (changed) {
+    decompose(model, transform);
+  }
+}
+
+void ScenePanel::drawGrid(ImVec2 origin, ImVec2 size) {
+  constexpr float GRID_STEP = 40.0f;
+  const ImU32 gridColor = IM_COL32(255, 255, 255, 18);
+  const ImVec2 end(origin.x + size.x, origin.y + size.y);
+
+  ImDrawList* drawList = ImGui::GetWindowDrawList();
+  for (float x = GRID_STEP; x < size.x; x += GRID_STEP) {
+    drawList->AddLine(ImVec2(origin.x + x, origin.y),
+                      ImVec2(origin.x + x, end.y), gridColor);
+  }
+  for (float y = GRID_STEP; y < size.y; y += GRID_STEP) {
+    drawList->AddLine(ImVec2(origin.x, origin.y + y),
+                      ImVec2(end.x, origin.y + y), gridColor);
+  }
+}
+
+void ScenePanel::handleCameraInput(const sophia::FrameInfo& frameInfo,
+                                   ImVec2 size) {
+  const ImGuiIO& io = ImGui::GetIO();
+  bool is3D = editorCamera.mode == EditorCamera::Mode::Scene3D;
+  glm::vec2 mouseDelta{io.MouseDelta.x, io.MouseDelta.y};
+
+  // The button stays active while any of its mouse buttons is held, even
+  // once the mouse leaves the panel.
+  if (ImGui::IsItemActive()) {
+    bool rightDown = ImGui::IsMouseDown(ImGuiMouseButton_Right);
+    bool middleDown = ImGui::IsMouseDown(ImGuiMouseButton_Middle);
+
+    if (is3D && rightDown) {
+      editorCamera.orbit(mouseDelta);
+
+      glm::vec3 direction{0.f};
+      if (ImGui::IsKeyDown(ImGuiKey_D)) direction.x += 1.f;
+      if (ImGui::IsKeyDown(ImGuiKey_A)) direction.x -= 1.f;
+      if (ImGui::IsKeyDown(ImGuiKey_E)) direction.y += 1.f;
+      if (ImGui::IsKeyDown(ImGuiKey_Q)) direction.y -= 1.f;
+      if (ImGui::IsKeyDown(ImGuiKey_S)) direction.z += 1.f;
+      if (ImGui::IsKeyDown(ImGuiKey_W)) direction.z -= 1.f;
+      editorCamera.fly(direction, static_cast<float>(frameInfo.deltaTime));
+    } else if (middleDown || (!is3D && rightDown)) {
+      editorCamera.pan(mouseDelta, size.y);
+    }
+  }
+
+  if (ImGui::IsItemHovered() && io.MouseWheel != 0.f) {
+    editorCamera.zoom(io.MouseWheel);
+  }
+
+  if (ImGui::IsWindowFocused() && !io.WantTextInput &&
+      ImGui::IsKeyPressed(ImGuiKey_F, false)) {
+    frameSelection();
+  }
+}
+
+void ScenePanel::handleSelectionInput(const ViewportTransform& viewport) {
+  const ImGuiIO& io = ImGui::GetIO();
+
+  if (ImGui::IsItemClicked(ImGuiMouseButton_Left)) {
+    context.selected = pick(viewport.screenToRay(io.MousePos));
+    // Dragging the selection around is 2D only; in 3D, use the gizmo.
+    dragging =
+        context.selected && editorCamera.mode == EditorCamera::Mode::Scene2D;
+  }
+
+  if (!ImGui::IsItemActive() || !ImGui::IsMouseDown(ImGuiMouseButton_Left)) {
+    dragging = false;
+    return;
+  }
+
+  if (dragging && (io.MouseDelta.x != 0.f || io.MouseDelta.y != 0.f)) {
+    ImVec2 previous(io.MousePos.x - io.MouseDelta.x,
+                    io.MousePos.y - io.MouseDelta.y);
+    glm::vec2 delta =
+        viewport.screenToWorld(io.MousePos) - viewport.screenToWorld(previous);
+
+    auto& transform =
+        context.selected.getComponent<sophia::TransformComponent>();
+    transform.position.x += delta.x;
+    transform.position.y += delta.y;
+  }
+}
+
+void ScenePanel::drawSelection(const ViewportTransform& viewport) {
+  sophia::Entity selected = context.selected;
+  if (!selected) {
+    return;
+  }
+
+  ImDrawList* drawList = ImGui::GetWindowDrawList();
+  const auto& transform = selected.getComponent<sophia::TransformComponent>();
+
+  if (selected.hasComponent<sophia::SpriteComponent>()) {
+    glm::mat4 model =
+        selected.getComponent<sophia::SpriteComponent>().getModel(transform);
+    for (size_t i = 0; i < UNIT_QUAD.size(); i++) {
+      const glm::vec2& from = UNIT_QUAD[i];
+      const glm::vec2& to = UNIT_QUAD[(i + 1) % UNIT_QUAD.size()];
+      viewport.drawLine(drawList, glm::vec3{model * glm::vec4{from, 0.f, 1.f}},
+                        glm::vec3{model * glm::vec4{to, 0.f, 1.f}},
+                        SELECTION_COLOR, 2.0f);
+    }
+  }
+
+  if (std::optional<sophia::AABB> bounds = getMeshBounds(selected)) {
+    glm::mat4 model = transform.mat4();
+    std::array<glm::vec3, 8> corners = bounds->getCorners();
+    for (glm::vec3& corner : corners) {
+      corner = glm::vec3{model * glm::vec4{corner, 1.f}};
+    }
+    // Corners whose indices differ in one bit share an edge.
+    for (int i = 0; i < 8; i++) {
+      for (int bit : {1, 2, 4}) {
+        if ((i & bit) == 0) {
+          viewport.drawLine(drawList, corners[i], corners[i | bit],
+                            SELECTION_COLOR, 2.0f);
+        }
+      }
+    }
+  }
+
+  // Mark the transform's position (the sprite's pivot), which is also all
+  // there is to show for entities without a sprite or mesh, such as the
+  // camera.
+  if (std::optional<ImVec2> center =
+          viewport.worldToScreen(transform.position)) {
+    drawList->AddCircle(*center, 4.0f, SELECTION_COLOR, 0, 2.0f);
+  }
+}
+
+void ScenePanel::frameSelection() {
+  sophia::Entity selected = context.selected;
+  if (!selected) {
+    return;
+  }
+
+  const auto& transform = selected.getComponent<sophia::TransformComponent>();
+
+  // The selection's corners in world space, from its mesh or sprite.
+  std::vector<glm::vec3> points;
+  if (std::optional<sophia::AABB> bounds = getMeshBounds(selected)) {
+    glm::mat4 model = transform.mat4();
+    for (const glm::vec3& corner : bounds->getCorners()) {
+      points.push_back(glm::vec3{model * glm::vec4{corner, 1.f}});
+    }
+  }
+  if (selected.hasComponent<sophia::SpriteComponent>()) {
+    glm::mat4 model =
+        selected.getComponent<sophia::SpriteComponent>().getModel(transform);
+    for (const glm::vec2& corner : UNIT_QUAD) {
+      points.push_back(glm::vec3{model * glm::vec4{corner, 0.f, 1.f}});
+    }
+  }
+
+  if (points.empty()) {
+    // Nothing with a size: frame a unit around its position.
+    editorCamera.frame(transform.position, 0.5f);
+    return;
+  }
+
+  glm::vec3 min = points.front();
+  glm::vec3 max = points.front();
+  for (const glm::vec3& point : points) {
+    min = glm::min(min, point);
+    max = glm::max(max, point);
+  }
+  editorCamera.frame((min + max) * 0.5f, glm::length(max - min) * 0.5f);
+}
+
+std::optional<sophia::AABB> ScenePanel::getMeshBounds(sophia::Entity entity) {
+  if (!entity.hasComponent<sophia::MeshComponent>()) {
+    return std::nullopt;
+  }
+  sophia::MeshHandle mesh = entity.getComponent<sophia::MeshComponent>().handle;
+  if (!resources.isAlive(mesh)) {
+    return std::nullopt;
+  }
+  return resources.getBounds(mesh);
+}
+
+sophia::Entity ScenePanel::pick(const Ray& ray) {
+  sophia::Scene& scene = context.getScene();
+
+  // Meshes are opaque and depth tested, so the nearest one hides anything
+  // behind it.
+  sophia::Entity nearestMesh;
+  float meshDistance = std::numeric_limits<float>::infinity();
+  scene.forEachEntity([&](sophia::Entity entity) {
+    std::optional<sophia::AABB> bounds = getMeshBounds(entity);
+    if (!bounds) {
+      return;
+    }
+    glm::mat4 model = entity.getComponent<sophia::TransformComponent>().mat4();
+    std::optional<float> distance =
+        intersectBox(ray.origin, ray.direction, model, *bounds);
+    if (distance && *distance < meshDistance) {
+      nearestMesh = entity;
+      meshDistance = *distance;
+    }
+  });
+
+  // Sprites in front of that mesh draw over it, in the renderer's order:
+  // higher sortOrder on top, then nearer.
+  sophia::Entity topSprite;
+  std::optional<std::tuple<sophia::s32, float>> topOrder;
+  scene.forEachEntity([&](sophia::Entity entity) {
+    if (!entity.hasComponent<sophia::SpriteComponent>()) {
+      return;
+    }
+    const auto& sprite = entity.getComponent<sophia::SpriteComponent>();
+    glm::mat4 model =
+        sprite.getModel(entity.getComponent<sophia::TransformComponent>());
+    std::optional<float> distance =
+        intersectQuad(ray.origin, ray.direction, model);
+    if (!distance || *distance > meshDistance) {
+      return;
+    }
+
+    // Negated distance, so nearer compares greater.
+    std::tuple order{sprite.sortOrder, -*distance};
+    if (!topOrder || order > *topOrder) {
+      topSprite = entity;
+      topOrder = order;
+    }
+  });
+
+  return topSprite ? topSprite : nearestMesh;
+}

editor/panels/scene_panel.hpp

@@ -0,0 +1,125 @@
+#pragma once
+
+#include <optional>
+#include <sophia/aabb.hpp>
+#include <sophia/entity.hpp>
+#include <sophia/frame_info.hpp>
+#include <sophia/handles.hpp>
+#include <sophia/math.hpp>
+#include <sophia/resource_registry_ref.hpp>
+#include <sophia/scene_view_registry.hpp>
+#include <sophia/ui/panel.hpp>
+#include <sophia/ui/ui.hpp>
+
+#include "../editor_camera.hpp"
+#include "../editor_context.hpp"
+
+/**
+ * Shows the active scene through the editor's own camera.
+ *
+ * 3D: right-drag orbits, middle-drag pans, the wheel zooms, right-drag with
+ * WASD/QE flies. 2D: right- or middle-drag pans, the wheel zooms. F frames
+ * the selection in both.
+ *
+ * The selection gets a transform gizmo: W moves, E rotates, R scales, and
+ * holding Ctrl snaps. Clicking selects the mesh or sprite under the mouse;
+ * in 2D, dragging it also moves it.
+ */
+class ScenePanel : public sophia::Panel {
+ public:
+  // Renders into `target` through `view`, a SceneView this panel keeps
+  // pointed at the active scene. `camera` is the entity the view looks
+  // through; it belongs to a scene of the editor's own, and this panel
+  // drives it from its EditorCamera.
+  ScenePanel(sophia::UI& ui, sophia::ResourceRegistryRef resources,
+             EditorContext& context, sophia::SceneViewRegistry& sceneViews,
+             sophia::SceneViewHandle view, sophia::RenderTargetHandle target,
+             sophia::Entity camera)
+      : Panel{{.name = "Scene", .windowFlags = WINDOW_FLAGS}},
+        ui{ui},
+        resources{resources},
+        context{context},
+        sceneViews{sceneViews},
+        view{view},
+        target{target},
+        camera{camera} {}
+
+  void onUpdate(const sophia::FrameInfo& frameInfo) override;
+
+ private:
+  static constexpr ImGuiWindowFlags WINDOW_FLAGS =
+      ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoScrollWithMouse;
+
+  enum class GizmoOperation { Translate, Rotate, Scale };
+
+  // A half-line in world space. `direction` is normalized, so distances
+  // along it are in world units.
+  struct Ray {
+    glm::vec3 origin;
+    glm::vec3 direction;
+  };
+
+  // Where the scene image is on screen this frame, and the camera looking
+  // through it.
+  struct ViewportTransform {
+    ImVec2 origin;
+    ImVec2 size;
+    glm::mat4 viewProjection;
+    glm::mat4 inverseViewProjection;
+
+    // Null for points behind the camera.
+    std::optional<ImVec2> worldToScreen(const glm::vec3& world) const;
+    // Where `screen` is on the camera's near plane. Only the x and y, which
+    // is all that's needed in 2D.
+    glm::vec2 screenToWorld(const ImVec2& screen) const;
+    // From the near plane through `screen`, into the scene.
+    Ray screenToRay(const ImVec2& screen) const;
+
+    // Draws a world-space line, cut off where it passes behind the camera.
+    void drawLine(ImDrawList* drawList, const glm::vec3& a, const glm::vec3& b,
+                  ImU32 color, float thickness) const;
+
+   private:
+    ImVec2 clipToScreen(const glm::vec4& clip) const;
+  };
+
+  void drawToolbar();
+  void drawGrid(ImVec2 origin, ImVec2 size);
+  void handleCameraInput(const sophia::FrameInfo& frameInfo, ImVec2 size);
+  void handleSelectionInput(const ViewportTransform& viewport);
+  void handleGizmoHotkeys();
+  // Draws the transform gizmo on the selection, and applies any change made
+  // with it. `view` is the editor camera's, and `aspect` the viewport's
+  // width over its height.
+  void drawGizmo(const glm::mat4& view, float aspect);
+  void drawSelection(const ViewportTransform& viewport);
+  void frameSelection();
+
+  // The bounds of the entity's mesh in the mesh's own space, if it has one.
+  std::optional<sophia::AABB> getMeshBounds(sophia::Entity entity);
+
+  // The entity drawn in front along `ray`, or a null Entity. Only meshes and
+  // sprites can be hit.
+  sophia::Entity pick(const Ray& ray);
+
+  sophia::UI& ui;
+  sophia::ResourceRegistryRef resources;
+  EditorContext& context;
+  sophia::SceneViewRegistry& sceneViews;
+  sophia::SceneViewHandle view;
+  sophia::RenderTargetHandle target;
+  sophia::Entity camera;
+
+  EditorCamera editorCamera;
+
+  GizmoOperation gizmoOperation = GizmoOperation::Translate;
+  // Whether the gizmo works along the entity's own axes or the world's.
+  bool gizmoLocal = true;
+  // Whether the viewport button was active last frame, i.e. a camera drag or
+  // click is under way, which the gizmo mustn't interrupt.
+  bool viewportActive = false;
+
+  bool showGrid = true;
+  // Set while a drag that started on the selected entity is moving it.
+  bool dragging = false;
+};

editor/utilities/logger.hpp

@@ -0,0 +1,13 @@
+#pragma once
+
+#include <format>
+#include <sophia/util/logger.hpp>
+#include <utility>
+
+template <typename... Args>
+void log(std::format_string<Args...> fmt, Args&&... args) {
+  if constexpr (sophia::log::enabled) {
+    sophia::log::print("\033[1;38;2;170;90;255m[editor]\033[0m {}",
+                       std::format(fmt, std::forward<Args>(args)...));
+  }
+}

engine/CMakeLists.txt

@@ -17,10 +17,22 @@ target_include_directories(${ENGINE_NAME} PUBLIC
   "${CMAKE_CURRENT_SOURCE_DIR}/include"
 )
 
+target_compile_definitions(${ENGINE_NAME} PUBLIC
+  GLM_FORCE_RADIANS
+  GLM_FORCE_DEPTH_ZERO_TO_ONE
+)
+
 target_link_libraries(${ENGINE_NAME} PUBLIC
   vulkan
+  vma
+  shaderc
   glfw
   glm
   imgui
   entt
+  Tracy::TracyClient
+)
+
+target_link_libraries(${ENGINE_NAME} PRIVATE
+  stb_image
 )

engine/include/sophia/aabb.hpp

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <array>
+#include <sophia/math.hpp>
+
+namespace sophia {
+
+/** @brief Axis-Aligned Bounding Box
+ *
+ * An axis-aligned box, from its smallest corner to its largest.
+ */
+struct AABB {
+  vec3 min{0.f, 0.f, 0.f};
+  vec3 max{0.f, 0.f, 0.f};
+
+  vec3 getCenter() const { return (min + max) * 0.5f; }
+  vec3 getSize() const { return max - min; }
+
+  // The 8 corners. Bit 0 of the index picks x from max, bit 1 y, bit 2 z.
+  std::array<vec3, 8> getCorners() const {
+    std::array<vec3, 8> corners;
+    for (int i = 0; i < 8; i++) {
+      corners[i] = {(i & 1) ? max.x : min.x, (i & 2) ? max.y : min.y,
+                    (i & 4) ? max.z : min.z};
+    }
+    return corners;
+  }
+};
+
+}  // namespace sophia

engine/include/sophia/application.hpp

@@ -3,20 +3,20 @@
 #include <cstdlib>
 #include <iostream>
 #include <memory>
-#include <sophia/asset_registry.hpp>
-#include <sophia/camera_2d.hpp>
 #include <sophia/canvas.hpp>
+#include <sophia/console/console_command_registry.hpp>
 #include <sophia/frame_info.hpp>
+#include <sophia/math.hpp>
+#include <sophia/resource_registry_ref.hpp>
+#include <sophia/scene_registry.hpp>
+#include <sophia/scene_view_registry.hpp>
 #include <sophia/types.hpp>
 #include <sophia/ui/debug_ui.hpp>
 #include <sophia/ui/panel_registry.hpp>
+#include <sophia/ui/ui.hpp>
 #include <string>
 #include <vector>
 
-#define GLM_FORCE_RADIANS
-#define GLM_FORCE_DEPTH_ZERO_TO_ONE
-#include <glm/glm.hpp>
-
 namespace sophia {
 
 class Application {
@@ -43,15 +43,19 @@ class Application {
   virtual void onRender() {}
   virtual void onDestroy() {}
 
-  AssetRegistry& assets() { return this->assetRegistry; }
+  ResourceRegistryRef resources();
   PanelRegistry& panels() { return this->panelRegistry; }
+  SceneRegistry& scenes() { return this->sceneRegistry; }
+  SceneViewRegistry& sceneViews() { return this->sceneViewRegistry; }
+  UI& ui() { return this->_ui; }
 
   DebugUI& debugUI() { return this->_debugUI; }
 
   Canvas canvas;
-  Camera2D camera;
   std::vector<std::string> args;
 
+  ConsoleCommandRegistry consoleCommandRegistry;
+
   void drawMesh(MeshHandle handle, const glm::mat4& transform);
 
  private:
@@ -63,8 +67,10 @@ class Application {
   class Impl;
   std::unique_ptr<Impl> impl;
 
-  AssetRegistry assetRegistry;
   PanelRegistry panelRegistry;
+  SceneRegistry sceneRegistry;
+  SceneViewRegistry sceneViewRegistry;
+  UI _ui;
 
   DebugUI _debugUI;
 };

engine/include/sophia/asset_registry.hpp

@@ -1,64 +0,0 @@
-#pragma once
-
-#include <memory>
-#include <sophia/handles.hpp>
-#include <string>
-#include <vector>
-
-#include "sophia/canvas.hpp"
-#include "sophia/types.hpp"
-
-namespace sophia {
-
-class Device;
-class Mesh;
-
-template <typename T>
-struct AssetTraits;
-
-template <>
-struct AssetTraits<Mesh> {
-  using Handle = MeshHandle;
-};
-
-class AssetRegistry {
- public:
-  ~AssetRegistry();
-
-  AssetRegistry(const AssetRegistry&) = delete;
-  AssetRegistry& operator=(const AssetRegistry&) = delete;
-
-  template <typename T>
-  typename AssetTraits<T>::Handle load(const std::string& path);
-
-  /**
-   * TEMPORARY: Remove once load<Mesh> can read real model files from disk.
-   */
-  MeshHandle loadMesh(std::vector<CanvasVertex> vertices,
-                      std::vector<u32> indices);
-
-  template <typename T>
-  void release(typename AssetTraits<T>::Handle handle);
-
- private:
-  friend class Application;
-
-  explicit AssetRegistry(Device& device);
-
-  template <typename T>
-  const T& get(typename AssetTraits<T>::Handle handle) const;
-
-  class Impl;
-  std::unique_ptr<Impl> impl;
-};
-
-template <>
-MeshHandle AssetRegistry::load<Mesh>(const std::string& path);
-
-template <>
-void AssetRegistry::release<Mesh>(MeshHandle handle);
-
-template <>
-const Mesh& AssetRegistry::get<Mesh>(MeshHandle handle) const;
-
-}  // namespace sophia

engine/include/sophia/camera_2d.hpp

@@ -1,30 +0,0 @@
-#pragma once
-
-#define GLM_FORCE_RADIANS
-#define GLM_FORCE_DEPTH_ZERO_TO_ONE
-#include <glm/glm.hpp>
-#include <glm/gtc/matrix_transform.hpp>
-
-namespace sophia {
-
-class Camera2D {
- public:
-  glm::vec2 position{0.f, 0.f};
-
-  void setProjection(float left, float right, float bottom, float top) {
-    projection = glm::ortho(left, right, bottom, top);
-  }
-
-  const glm::mat4& getProjection() const { return projection; }
-
-  glm::mat4 getView() const {
-    return glm::translate(glm::mat4(1.f), glm::vec3(-position, 0.f));
-  }
-
-  glm::mat4 getViewProjection() const { return projection * getView(); }
-
- private:
-  glm::mat4 projection{1.f};
-};
-
-}  // namespace sophia

engine/include/sophia/canvas.hpp

@@ -2,12 +2,9 @@
 
 #include <memory>
 #include <sophia/frame_info.hpp>
+#include <sophia/math.hpp>
 #include <vector>
 
-#define GLM_FORCE_RADIANS
-#define GLM_FORCE_DEPTH_ZERO_TO_ONE
-#include <glm/glm.hpp>
-
 namespace sophia {
 
 class Application;

engine/include/sophia/components.hpp

@@ -1,18 +1,17 @@
 #pragma once
 
-#include <sophia/asset_registry.hpp>
-#include <string>
-
-#define GLM_FORCE_RADIANS
-#define GLM_FORCE_DEPTH_ZERO_TO_ONE
-#include <glm/glm.hpp>
 #include <glm/gtc/matrix_transform.hpp>
-#include <glm/gtc/quaternion.hpp>
+#include <iostream>
+#include <ostream>
+#include <sophia/handles.hpp>
+#include <sophia/math.hpp>
+#include <string>
 
 namespace sophia {
 
 struct TagComponent {
   std::string tag;  // entt::hashed_string ?
+  uint32_t mask = 0;
 };
 
 struct TransformComponent {
@@ -28,10 +27,117 @@ struct TransformComponent {
   glm::mat3 normalMatrix() const {
     return glm::mat3{glm::transpose(glm::inverse(mat4()))};
   }
+
+  friend std::ostream& operator<<(std::ostream& os,
+                                  const TransformComponent& transform) {
+    os << "TransformComponent {\n"
+       << "  Position: (" << transform.position.x << ", "
+       << transform.position.y << ", " << transform.position.z << ")\n"
+       << "  Rotation (w, x, y, z): (" << transform.rotation.w << ", "
+       << transform.rotation.x << ", " << transform.rotation.y << ", "
+       << transform.rotation.z << ")\n"
+       << "  Scale: (" << transform.scale.x << ", " << transform.scale.y << ", "
+       << transform.scale.z << ")\n"
+       << "}";
+    return os;
+  }
 };
 
+/**
+ * Draws a mesh, placed by the entity's TransformComponent. Opaque and unlit
+ * for now.
+ */
 struct MeshComponent {
   MeshHandle handle;
+  // Multiplied with the mesh's vertex colors. Alpha is ignored. Stands in for
+  // a material until there are materials.
+  glm::vec4 color{1.f, 1.f, 1.f, 1.f};
+};
+
+/**
+ * A textured quad in the XY plane, placed by the entity's TransformComponent.
+ * Only rotation around Z is meaningful.
+ */
+struct SpriteComponent {
+  // Invalid draws a solid quad in `color`.
+  TextureHandle texture = INVALID_HANDLE;
+  glm::vec4 color{1.f, 1.f, 1.f, 1.f};
+
+  // Size in world units, before the transform's scale.
+  glm::vec2 size{1.f, 1.f};
+  // Point on the sprite, from (0, 0) at its bottom-left to (1, 1) at its
+  // top-right, that sits at the transform's position and that it rotates
+  // around.
+  glm::vec2 pivot{0.5f, 0.5f};
+  // Region of the texture to draw, as normalized (u0, v0, u1, v1) with
+  // (0, 0) at the texture's top-left.
+  glm::vec4 uvRect{0.f, 0.f, 1.f, 1.f};
+
+  // Higher draws on top, whatever the depth. Sprites with the same sortOrder
+  // draw back to front from the camera; the transform's position.z is depth
+  // like any other axis, not a layer.
+  s32 sortOrder = 0;
+
+  // Maps the unit quad (0, 0)-(1, 1) to world space: to the sprite's
+  // rectangle around its pivot, then by `transform`.
+  glm::mat4 getModel(const TransformComponent& transform) const {
+    return transform.mat4() *
+           glm::translate(glm::mat4{1.f}, glm::vec3{-pivot * size, 0.f}) *
+           glm::scale(glm::mat4{1.f}, glm::vec3{size, 1.f});
+  }
+};
+
+struct CameraComponent {
+  struct Orthographic {
+    float height = 10.f;
+    float nearPlane = -1000.f;
+    float farPlane = 1000.f;
+  };
+
+  struct Perspective {
+    float fov = glm::radians(60.f);
+    float nearPlane = 0.1f;
+    float farPlane = 100.f;
+  };
+
+  enum class Projection { Orthographic, Perspective };
+
+  Projection projection = Projection::Orthographic;
+  Orthographic ortho;
+  Perspective perspective;
+
+  // View -> clip space. World +Y is up on screen: Vulkan's clip space has +Y
+  // pointing down, so the projection flips it.
+  glm::mat4 getProjection(float aspect) const {
+    glm::mat4 result;
+    if (projection == Projection::Perspective) {
+      result = glm::perspective(perspective.fov, aspect, perspective.nearPlane,
+                                perspective.farPlane);
+    } else {
+      float halfHeight = ortho.height / 2.f;
+      float halfWidth = halfHeight * aspect;
+      result = glm::ortho(-halfWidth, halfWidth, -halfHeight, halfHeight,
+                          ortho.nearPlane, ortho.farPlane);
+    }
+
+    result[1][1] *= -1.f;
+    return result;
+  }
+
+  // World -> view space for this camera placed by `transform`. Ignores the
+  // transform's scale; zoom is the projection's job. The camera looks down
+  // view-space -Z.
+  static glm::mat4 getView(const TransformComponent& transform) {
+    glm::mat4 world = glm::translate(glm::mat4{1.f}, transform.position) *
+                      glm::mat4_cast(transform.rotation);
+    return glm::inverse(world);
+  }
+
+  // World -> clip space for this camera placed by `transform`.
+  glm::mat4 getViewProjection(const TransformComponent& transform,
+                              float aspect) const {
+    return getProjection(aspect) * getView(transform);
+  }
 };
 
 }  // namespace sophia

engine/include/sophia/console/console_command_registry.hpp

@@ -0,0 +1,35 @@
+#pragma once
+
+#include <functional>
+#include <map>
+#include <string>
+#include <vector>
+
+namespace sophia {
+
+class ConsoleCommandRegistry {
+ public:
+  using Handler = std::function<std::string(const std::vector<std::string>&)>;
+
+  struct CommandInfo {
+    std::string name;
+    std::string help;
+  };
+
+  void registerCommand(std::string name, std::string help, Handler handler);
+
+  bool dispatch(const std::string& name, const std::vector<std::string>& args,
+                std::string& outResult) const;
+
+  std::vector<CommandInfo> list() const;
+
+ private:
+  struct Command {
+    std::string help;
+    Handler handler;
+  };
+
+  std::map<std::string, Command> commands;
+};
+
+}  // namespace sophia

engine/include/sophia/entity.hpp

@@ -0,0 +1,69 @@
+#pragma once
+
+#include <entt/entt.hpp>
+#include <sophia/scene.hpp>
+#include <sophia/types.hpp>
+#include <sophia/util/assert.hpp>
+
+namespace sophia {
+
+class Entity {
+ public:
+  Entity(const Entity&) = default;
+  Entity& operator=(const Entity&) = default;
+
+  Entity() = default;
+  Entity(entt::entity handle, Scene* scene);
+
+  template <typename T, typename... Args>
+  T& addComponent(Args&&... args) {
+    SOPHIA_ASSERT(!hasComponent<T>(), "Entity already has component!");
+    T& component =
+        scene->registry.emplace<T>(handle, std::forward<Args>(args)...);
+    // scene->OnComponentAdded<T>(*this, component);
+    return component;
+  }
+
+  template <typename T>
+  T& getComponent() {
+    SOPHIA_ASSERT(hasComponent<T>(), "Entity does not have component!");
+    return scene->registry.get<T>(handle);
+  }
+
+  template <typename T>
+  bool hasComponent() {
+    return scene->registry.all_of<T>(handle);
+  }
+
+  template <typename T>
+  void removeComponent() {
+    SOPHIA_ASSERT(hasComponent<T>(), "Entity does not have component!");
+    scene->registry.remove<T>(handle);
+  }
+
+  operator bool() const { return handle != entt::null; }
+  operator entt::entity() const { return handle; }
+  operator u32() const { return (u32)handle; }
+
+  // UUID GetUUID() { return GetComponent<IDComponent>().ID; }
+  // const std::string& GetName() { return GetComponent<TagComponent>().Tag; }
+
+  bool operator==(const Entity& other) const {
+    return handle == other.handle && scene == other.scene;
+  }
+
+  bool operator!=(const Entity& other) const { return !(*this == other); }
+
+ private:
+  entt::entity handle{entt::null};
+  Scene* scene = nullptr;
+};
+
+template <typename Fn>
+void Scene::forEachEntity(Fn&& fn) {
+  for (auto [handle] : registry.storage<entt::entity>().each()) {
+    fn(Entity{handle, this});
+  }
+}
+
+}  // namespace sophia

engine/include/sophia/event.hpp

@@ -2,12 +2,11 @@
 
 #include <any>
 #include <functional>
-#include <string>
-#include <unordered_map>
-
 #include <sophia/types.hpp>
 #include <sophia/util/delegate.hpp>
 #include <sophia/util/logger.hpp>
+#include <string>
+#include <unordered_map>
 
 #define BIT(x) (1 << (x))
 
@@ -84,7 +83,7 @@ class EventSystem {
       this->eventDelegates[eventType] =
           std::make_unique<std::any>(EventDelegate<E>());
 
-      log::trace("EventSystem creating new event type: ", eventType);
+      log::trace("EventSystem creating new event type: {}", eventType);
     }
 
     EventDelegate<E>& delegate =
@@ -103,7 +102,7 @@ class EventSystem {
       this->eventDelegates[eventType] =
           std::make_unique<std::any>(EventDelegate<E>());
 
-      log::trace("EventSystem creating new event type: ", eventType);
+      log::trace("EventSystem creating new event type: {}", eventType);
     }
 
     EventDelegate<E>& delegate =
@@ -116,19 +115,23 @@ class EventSystem {
     static_assert(std::is_base_of<Event, E>::value, "E must derive from Event");
     EventType eventType = GET_EVENT_TYPE(E);
 
-    if (!this->eventDelegates.count(eventType)) { return; }
+    if (!this->eventDelegates.count(eventType)) {
+      return;
+    }
 
     try {
       EventDelegate<E>& delegate =
           std::any_cast<EventDelegate<E>&>(*this->eventDelegates.at(eventType));
       delegate.invoke(event);
     } catch (const std::out_of_range& error) {
-      log::error("event dispatch failed: ", event.toString());
+      log::error("event dispatch failed: {}", event.toString());
     }
   }
 
  private:
-  EventSystem() { log::info("EventSystem Initialized: ", this); }
+  EventSystem() {
+    log::info("EventSystem Initialized: {}", static_cast<const void*>(this));
+  }
   ~EventSystem() { log::info("EventSystem Destroyed"); }
 
   std::unordered_map<EventType, std::unique_ptr<std::any>> eventDelegates;

engine/include/sophia/frame_info.hpp

@@ -1,12 +1,8 @@
 #pragma once
 
-#include <sophia/camera_2d.hpp>
+#include <sophia/math.hpp>
 #include <sophia/types.hpp>
 
-#define GLM_FORCE_RADIANS
-#define GLM_FORCE_DEPTH_ZERO_TO_ONE
-#include <glm/glm.hpp>
-
 namespace sophia {
 
 struct FrameInfo {
@@ -14,7 +10,6 @@ struct FrameInfo {
   double elapsedTime;
   double deltaTime;
   glm::vec2 currentFramebufferExtent;
-  const Camera2D& camera;
 };
 
 }  // namespace sophia

engine/include/sophia/handles.hpp

@@ -6,7 +6,7 @@
 
 namespace sophia {
 
-template <typename Tag>
+template <typename T>
 struct Handle {
   static constexpr u32 INVALID_INDEX = (1u << 20) - 1;
 
@@ -24,10 +24,27 @@ struct Handle {
   [[nodiscard]] auto operator<=>(const Handle&) const = default;
 };
 
-struct MeshTag {};
+struct InvalidHandle {
-struct PanelTag {};
+  template <typename T>
+  [[nodiscard]] constexpr operator Handle<T>() const {
+    return Handle<T>::invalid();
+  }
+};
 
-using MeshHandle = Handle<MeshTag>;
+inline constexpr InvalidHandle INVALID_HANDLE{};
-using PanelHandle = Handle<PanelTag>;
+
+class Mesh;
+class Panel;
+class RenderTarget;
+class Scene;
+struct SceneView;
+class Texture;
+
+using MeshHandle = Handle<Mesh>;
+using PanelHandle = Handle<Panel>;
+using RenderTargetHandle = Handle<RenderTarget>;
+using SceneHandle = Handle<Scene>;
+using SceneViewHandle = Handle<SceneView>;
+using TextureHandle = Handle<Texture>;
 
 }  // namespace sophia

engine/include/sophia/math.hpp

@@ -0,0 +1,17 @@
+#pragma once
+
+#include <glm/glm.hpp>
+#include <glm/gtc/quaternion.hpp>
+
+namespace sophia {
+
+using vec2 = glm::vec2;
+using vec3 = glm::vec3;
+using vec4 = glm::vec4;
+using ivec2 = glm::ivec2;
+using uvec2 = glm::uvec2;
+using mat3 = glm::mat3;
+using mat4 = glm::mat4;
+using quat = glm::quat;
+
+}  // namespace sophia

engine/include/sophia/mesh_data.hpp

@@ -0,0 +1,29 @@
+#pragma once
+
+#include <sophia/math.hpp>
+#include <sophia/types.hpp>
+#include <vector>
+
+namespace sophia {
+
+// Layout must match the per-vertex inputs in mesh.vert.
+struct MeshVertex {
+  vec3 position{0.f, 0.f, 0.f};
+  vec3 normal{0.f, 0.f, 1.f};
+  // Texture coordinates, with (0, 0) at the texture's top-left.
+  vec2 uv{0.f, 0.f};
+  vec4 color{1.f, 1.f, 1.f, 1.f};
+};
+
+/**
+ * Geometry on the CPU, uploaded with `resources().create<Mesh>(data)`.
+ * Triangles wind counter-clockwise when seen from the front; back faces are
+ * culled. See primitives.hpp for ready-made shapes.
+ */
+struct MeshData {
+  std::vector<MeshVertex> vertices;
+  // Empty draws the vertices in order, three per triangle.
+  std::vector<u32> indices;
+};
+
+}  // namespace sophia

engine/include/sophia/primitives.hpp

@@ -0,0 +1,18 @@
+#pragma once
+
+#include <sophia/math.hpp>
+#include <sophia/mesh_data.hpp>
+
+/**
+ * Ready-made shapes, centered on the origin. They return MeshData rather than
+ * a mesh so they can be adjusted before uploading:
+ *
+ *   MeshHandle cube = resources().create<Mesh>(primitives::cube());
+ */
+namespace sophia::primitives {
+
+// An axis-aligned cube `size` across. Each face has its own four vertices so
+// it gets its own normal and UVs.
+MeshData cube(float size = 1.f, vec4 color = vec4{1.f});
+
+}  // namespace sophia::primitives

engine/include/sophia/resource_registry_ref.hpp

@@ -0,0 +1,74 @@
+#pragma once
+
+#include <sophia/aabb.hpp>
+#include <sophia/handles.hpp>
+#include <sophia/math.hpp>
+#include <sophia/mesh_data.hpp>
+#include <sophia/types.hpp>
+#include <string>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+namespace sophia {
+
+class ResourceRegistry;
+
+class ResourceRegistryRef {
+ public:
+  template <typename T>
+  Handle<T> load(const std::string& path);
+
+  template <typename T, typename... Args>
+  Handle<T> create(Args&&... args) {
+    return createResource(std::type_identity<T>{}, std::forward<Args>(args)...);
+  }
+
+  void requestResize(RenderTargetHandle handle, u32 width, u32 height);
+
+  glm::vec2 getExtent(RenderTargetHandle handle) const;
+  glm::vec2 getExtent(TextureHandle handle) const;
+
+  // In the mesh's own space.
+  AABB getBounds(MeshHandle handle) const;
+
+  bool isAlive(MeshHandle handle) const;
+  bool isAlive(RenderTargetHandle handle) const;
+  bool isAlive(TextureHandle handle) const;
+
+  template <typename T>
+  void release(Handle<T> handle);
+
+ private:
+  friend class Application;
+
+  explicit ResourceRegistryRef(ResourceRegistry& registry)
+      : registry{&registry} {}
+
+  MeshHandle createResource(std::type_identity<Mesh>, const MeshData& data);
+
+  RenderTargetHandle createResource(std::type_identity<RenderTarget>,
+                                    u32 width = 1, u32 height = 1);
+
+  TextureHandle createResource(std::type_identity<Texture>, u32 width,
+                               u32 height, std::vector<u8> pixels);
+
+  ResourceRegistry* registry;
+};
+
+template <>
+MeshHandle ResourceRegistryRef::load<Mesh>(const std::string& path);
+
+template <>
+TextureHandle ResourceRegistryRef::load<Texture>(const std::string& path);
+
+template <>
+void ResourceRegistryRef::release<Mesh>(MeshHandle handle);
+
+template <>
+void ResourceRegistryRef::release<RenderTarget>(RenderTargetHandle handle);
+
+template <>
+void ResourceRegistryRef::release<Texture>(TextureHandle handle);
+
+}  // namespace sophia

engine/include/sophia/scene.hpp

@@ -0,0 +1,44 @@
+#pragma once
+
+#include <entt/entt.hpp>
+#include <string>
+
+namespace sophia {
+
+class Entity;
+class SceneRenderer;  // !TEMP remove this
+
+class Scene {
+ public:
+  Scene();
+  ~Scene();
+
+  Entity createEntity(const std::string& name = {});
+  void destroyEntity(Entity entity);
+
+  Entity createCamera(const std::string& name = "Camera");
+
+  /** Calls `fn(Entity)` for every live entity. Defined in entity.hpp. */
+  template <typename Fn>
+  void forEachEntity(Fn&& fn);
+
+  Entity getActiveCamera();
+  void setActiveCamera(Entity camera);
+
+  bool isVisible() const { return this->visible; }
+  void setVisible(bool visible) { this->visible = visible; }
+
+  bool isActive() const { return this->active; }
+  void setActive(bool active) { this->active = active; }
+
+ private:
+  friend class Entity;
+  friend class SceneRenderer;  // !TEMP remove this
+
+  entt::registry registry;
+  entt::entity activeCamera = entt::null;
+  bool visible = true;
+  bool active = true;
+};
+
+}  // namespace sophia

engine/include/sophia/scene_registry.hpp

@@ -0,0 +1,33 @@
+#pragma once
+
+#include <sophia/handles.hpp>
+#include <sophia/scene.hpp>
+#include <sophia/util/pool.hpp>
+
+namespace sophia {
+
+class SceneRegistry {
+ public:
+  SceneRegistry(const SceneRegistry&) = delete;
+  SceneRegistry& operator=(const SceneRegistry&) = delete;
+
+  SceneRegistry() = default;
+  ~SceneRegistry() = default;
+
+  SceneHandle create() { return pool.create(); }
+
+  const Scene& get(SceneHandle handle) const { return pool.get(handle); }
+  Scene& get(SceneHandle handle) { return pool.get(handle); }
+
+  const Scene& peek(SceneHandle handle) const { return pool.get(handle); }
+
+  void release(SceneHandle handle) { pool.release(handle); }
+  bool isAlive(SceneHandle handle) const { return pool.isAlive(handle); }
+
+  u32 size() const { return pool.size(); }
+
+ private:
+  Pool<Scene> pool{"Scene"};
+};
+
+}  // namespace sophia

engine/include/sophia/scene_view.hpp

@@ -0,0 +1,38 @@
+#pragma once
+
+#include <sophia/entity.hpp>
+#include <sophia/handles.hpp>
+#include <sophia/math.hpp>
+#include <sophia/scene.hpp>
+
+namespace sophia {
+
+enum class ClearFlags : u8 {
+  None = 0,
+  Color = 1 << 0,
+  Depth = 1 << 1,
+  Stencil = 1 << 2,
+  All = Color | Depth | Stencil
+};
+
+struct SceneView {
+  SceneHandle scene = INVALID_HANDLE;
+  RenderTargetHandle target =
+      INVALID_HANDLE;  // null implies render to swapchain
+  // Null implies the scene's active camera. May belong to another scene,
+  // e.g. an editor camera that isn't part of the scene being shown.
+  Entity camera;
+
+  // TODO(#76): not used yet; every view renders to its whole target.
+  vec4 viewport{0.0f, 0.0f, 1.0f, 1.0f};
+
+  vec4 clearColor{0.f, 0.f, 0.f, 1.f};
+  ClearFlags clearFlags = ClearFlags::All;
+
+  u32 priority = 0;  // Lower priority renders first
+  u32 layerMask = 0xFFFFFFFF;
+
+  bool enabled = true;  // Disabled views are kept but not rendered
+};
+
+}  // namespace sophia

engine/include/sophia/scene_view_registry.hpp

@@ -0,0 +1,90 @@
+#pragma once
+
+#include <algorithm>
+#include <sophia/handles.hpp>
+#include <sophia/scene_view.hpp>
+#include <sophia/util/pool.hpp>
+#include <utility>
+#include <vector>
+
+namespace sophia {
+
+/**
+ * Every live SceneView. The application renders all enabled views each frame,
+ * in ascending priority order, before the UI.
+ */
+class SceneViewRegistry {
+ public:
+  SceneViewRegistry(const SceneViewRegistry&) = delete;
+  SceneViewRegistry& operator=(const SceneViewRegistry&) = delete;
+
+  SceneViewRegistry() = default;
+  ~SceneViewRegistry() = default;
+
+  SceneViewHandle create(const SceneView& view = {}) {
+    isRenderQueueDirty = true;
+    return pool.create(view);
+  }
+
+  const SceneView& get(SceneViewHandle handle) const {
+    return pool.get(handle);
+  }
+
+  SceneView& get(SceneViewHandle handle) {
+    isRenderQueueDirty = true;
+    return pool.get(handle);
+  }
+
+  const SceneView& peek(SceneViewHandle handle) const {
+    return pool.get(handle);
+  }
+
+  void release(SceneViewHandle handle) {
+    isRenderQueueDirty = true;
+    pool.release(handle);
+  }
+
+  bool isAlive(SceneViewHandle handle) const { return pool.isAlive(handle); }
+
+  u32 size() const { return pool.size(); }
+
+  template <typename Fn>
+  void forEach(Fn&& fn) {
+    isRenderQueueDirty = true;
+    pool.forEach(std::forward<Fn>(fn));
+  }
+
+  template <typename Fn>
+  void forEach(Fn&& fn) const {
+    pool.forEach(std::forward<Fn>(fn));
+  }
+
+  const std::vector<SceneViewHandle>& GetRenderQueue() const {
+    if (isRenderQueueDirty) {
+      rebuildRenderQueue();
+    }
+    return renderQueue;
+  }
+
+ private:
+  void rebuildRenderQueue() const {
+    renderQueue.clear();
+    pool.forEachWithHandle([&](SceneViewHandle handle, const SceneView& view) {
+      if (view.enabled) {
+        renderQueue.push_back(handle);
+      }
+    });
+
+    std::ranges::stable_sort(renderQueue, {}, [this](SceneViewHandle handle) {
+      return pool.get(handle).priority;
+    });
+    isRenderQueueDirty = false;
+  }
+
+  Pool<SceneView> pool{"SceneView"};
+
+  mutable std::vector<SceneViewHandle> renderQueue;
+  mutable bool isRenderQueueDirty = true;
+};
+
+}  // namespace sophia

engine/include/sophia/ui/debug_ui.hpp

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <sophia/console/console_command_registry.hpp>
 #include <sophia/handles.hpp>
 #include <sophia/ui/panel_registry.hpp>
 
@@ -10,15 +11,15 @@ class DebugUI {
   DebugUI(const DebugUI&) = delete;
   DebugUI& operator=(const DebugUI&) = delete;
 
-  explicit DebugUI(PanelRegistry& registry);
+  DebugUI(PanelRegistry& registry, ConsoleCommandRegistry& commands);
   ~DebugUI() = default;
 
   void show();
   void hide();
 
-  void showPanelRegistry(bool show = true);
+  void showPanelRegistry(bool show = false);
-  void showFrameStats(bool show = true);
+  void showFrameStats(bool show = false);
-  void showConsole(bool show = true);
+  void showConsole(bool show = false);
 
  private:
   PanelRegistry& registry;

engine/include/sophia/ui/dock_layout.hpp

@@ -0,0 +1,23 @@
+#pragma once
+
+#include <string>
+#include <vector>
+
+namespace sophia {
+
+struct DockLayout {
+  float leftWidth = 0.2f;
+  float rightWidth = 0.25f;
+  float bottomHeight = 0.25f;
+
+  std::vector<std::string> left;
+  std::vector<std::string> right;
+  std::vector<std::string> bottom;
+  std::vector<std::string> center;
+
+  bool empty() const {
+    return left.empty() && right.empty() && bottom.empty() && center.empty();
+  }
+};
+
+}  // namespace sophia

engine/include/sophia/ui/panel.hpp

@@ -1,5 +1,9 @@
 #pragma once
 
+#include <imgui.h>
+
+#include <glm/glm.hpp>
+#include <optional>
 #include <sophia/frame_info.hpp>
 #include <string>
 #include <utility>
@@ -8,28 +12,54 @@ namespace sophia {
 
 class Panel {
  public:
+  struct Config {
+    const std::string name;
+
+    ImGuiWindowFlags windowFlags = ImGuiWindowFlags_None;
+    ImGuiDockNodeFlags dockNodeFlags = ImGuiDockNodeFlags_None;
+
+    bool locked = false;
+    bool closable = true;
+
+    glm::vec2 size{0.0f, 0.0f};
+    std::optional<glm::vec2> position;
+
+    ImGuiWindowFlags getWindowFlags() const;
+    ImGuiDockNodeFlags getDockNodeFlags() const;
+    bool hasCloseButton() const;
+    ImGuiCond getPlacementCond() const;
+  };
+
   Panel(const Panel&) = delete;
   Panel& operator=(const Panel&) = delete;
 
   Panel(Panel&&) noexcept = default;
-  Panel& operator=(Panel&&) noexcept = default;
+  Panel& operator=(Panel&&) = delete;
 
-  explicit Panel(std::string name = {}) : name{std::move(name)} {}
+  explicit Panel(Config config) : config{std::move(config)} {}
   virtual ~Panel() = default;
 
-  virtual void onUpdate(const FrameInfo& frameInfo) = 0;
+  void draw(const FrameInfo& frameInfo);
 
-  const std::string& getName() const { return name; }
+  Config& getConfig() { return config; }
+  const Config& getConfig() const { return config; }
+
+  const std::string& getName() const { return config.name; }
+  bool isLocked() const { return config.locked; }
 
   bool isVisible() const { return this->visible; }
+  bool isShown() const { return this->visible && this->shown; }
   void setVisible(bool visible) { this->visible = visible; }
   void toggleVisible() { this->visible = !this->visible; }
 
  protected:
+  virtual void onUpdate(const FrameInfo& frameInfo) = 0;
+
   bool visible = true;
+  bool shown = false;
 
  private:
-  std::string name;
+  Config config;
 };
 
 }  // namespace sophia

engine/include/sophia/ui/panel_registry.hpp

@@ -3,8 +3,10 @@
 #include <memory>
 #include <sophia/frame_info.hpp>
 #include <sophia/handles.hpp>
+#include <sophia/ui/dock_layout.hpp>
 #include <sophia/ui/panel.hpp>
 #include <sophia/util/assert.hpp>
+#include <sophia/util/pool.hpp>
 #include <string_view>
 #include <typeinfo>
 #include <utility>
@@ -20,23 +22,23 @@ class PanelRegistry {
   PanelRegistry() = default;
   ~PanelRegistry() = default;
 
-  PanelHandle add(std::unique_ptr<Panel> panel);
+  PanelHandle add(std::unique_ptr<Panel> panel) {
+    return pool.add(std::move(panel));
+  }
 
   template <typename T, typename... Args>
   PanelHandle emplace(Args&&... args) {
     return add(std::make_unique<T>(std::forward<Args>(args)...));
   }
 
-  const Panel& get(PanelHandle handle) const;
+  const Panel& get(PanelHandle handle) const { return pool.get(handle); }
-  Panel& get(PanelHandle handle) {
+  Panel& get(PanelHandle handle) { return pool.get(handle); }
-    return const_cast<Panel&>(std::as_const(*this).get(handle));
-  }
 
   template <typename T>
   const T& get(PanelHandle handle) const {
     const Panel& panel = get(handle);
     SOPHIA_ASSERT(dynamic_cast<const T*>(&panel) != nullptr,
-                  "PanelHandle does not refer to a", typeid(T).name());
+                  "PanelHandle does not refer to a {}", typeid(T).name());
     return static_cast<const T&>(panel);
   }
 
@@ -45,19 +47,17 @@ class PanelRegistry {
     return const_cast<T&>(std::as_const(*this).template get<T>(handle));
   }
 
-  void remove(PanelHandle handle);
+  void remove(PanelHandle handle) { pool.release(handle); }
-  bool isValid(PanelHandle handle) const;
+  bool isValid(PanelHandle handle) const { return pool.isAlive(handle); }
 
   template <typename T>
   const T* find() const {
-    for (const Slot& slot : slots) {
+    const T* result = nullptr;
-      if (slot.panel) {
+    pool.findIf([&result](const Panel& panel) {
-        if (const T* panel = dynamic_cast<const T*>(slot.panel.get())) {
+      result = dynamic_cast<const T*>(&panel);
-          return panel;
+      return result != nullptr;
-        }
+    });
-      }
+    return result;
-    }
-    return nullptr;
   }
 
   template <typename T>
@@ -66,42 +66,35 @@ class PanelRegistry {
   }
 
   const Panel* find(std::string_view name) const {
-    for (const Slot& slot : slots) {
+    return pool.findIf(
-      if (slot.panel && slot.panel->getName() == name) {
+        [name](const Panel& panel) { return panel.getName() == name; });
-        return slot.panel.get();
-      }
-    }
-    return nullptr;
   }
 
   Panel* find(std::string_view name) {
     return const_cast<Panel*>(std::as_const(*this).find(name));
   }
 
-  u32 size() const;
+  u32 size() const { return pool.size(); }
   u32 visibleCount() const;
 
   std::vector<std::string_view> names() const {
     std::vector<std::string_view> result;
-    result.reserve(slots.size());
+    result.reserve(pool.size());
-    for (const Slot& slot : slots) {
+    pool.forEach(
-      if (slot.panel) {
+        [&result](const Panel& panel) { result.push_back(panel.getName()); });
-        result.push_back(slot.panel->getName());
-      }
-    }
     return result;
   }
 
   void update(const FrameInfo& frameInfo);
 
- private:
+  void setDefaultLayout(DockLayout layout) {
-  struct Slot {
+    defaultLayout = std::move(layout);
-    std::unique_ptr<Panel> panel;
+  }
-    u32 generation = 0;
+  const DockLayout& getDefaultLayout() const { return defaultLayout; }
-  };
 
-  std::vector<Slot> slots;
+ private:
-  std::vector<u32> freeList;
+  Pool<Panel> pool{"Panel"};
+  DockLayout defaultLayout;
 };
 
 }  // namespace sophia

engine/include/sophia/ui/ui.hpp

@@ -0,0 +1,40 @@
+#pragma once
+
+#include <imgui.h>
+
+#include <sophia/handles.hpp>
+#include <sophia/resource_registry_ref.hpp>
+
+namespace sophia {
+
+class ImGuiRenderer;
+
+class UI {
+ public:
+  UI(const UI&) = delete;
+  UI& operator=(const UI&) = delete;
+
+  /**
+   * Draws the target filling the space left in the current window, and keeps
+   * the target sized to match. The target catches up on the next frame, so the
+   * image may be a frame behind while the window is being resized.
+   */
+  void image(RenderTargetHandle handle);
+
+  /**
+   * Texture to hand to ImGui::Image() that shows the target's contents.
+   * Changes when the target is resized, so fetch it each frame rather than
+   * caching it.
+   */
+  ImTextureID getTextureId(RenderTargetHandle handle);
+
+ private:
+  friend class Application;
+
+  explicit UI(ResourceRegistryRef resources) : resources{resources} {}
+
+  ResourceRegistryRef resources;
+  ImGuiRenderer* renderer = nullptr;
+};
+
+}  // namespace sophia

engine/include/sophia/util/assert.hpp

@@ -1,7 +1,9 @@
 /**
  * Usage:
  * SOPHIA_ASSERT(pipelineLayout != nullptr);
- * SOPHIA_ASSERT(index < count, "index", index, "out of bounds:", count);
+ * SOPHIA_ASSERT(index < count, "index {} out of bounds: {}", index, count);
+ *
+ * The optional message is a std::format string, checked at compile time.
  *
  * Compiled out entirely in release (NDEBUG) builds, matching <cassert>'s
  * assert() semantics: don't rely on side effects inside the condition.
@@ -10,16 +12,18 @@
 #pragma once
 
 #include <cstdlib>
+#include <format>
 #include <sophia/util/logger.hpp>
 
 #ifndef NDEBUG
-#define SOPHIA_ASSERT(condition, ...)                                       \
+#define SOPHIA_ASSERT(condition, ...)                                      \
-  do {                                                                      \
+  do {                                                                     \
-    if (!(condition)) {                                                     \
+    if (!(condition)) {                                                    \
-      ::sophia::log::fatal("Assertion failed:", #condition, "at", __FILE__, \
+      ::sophia::log::fatal(                                                \
-                           ":", __LINE__ __VA_OPT__(, ) __VA_ARGS__);       \
+          "Assertion failed: {} at {}:{}" __VA_OPT__(" - {}"), #condition, \
-      std::abort();                                                         \
+          __FILE__, __LINE__ __VA_OPT__(, ::std::format(__VA_ARGS__)));    \
-    }                                                                       \
+      std::abort();                                                        \
+    }                                                                      \
   } while (false)
 #else
 #define SOPHIA_ASSERT(condition, ...) ((void)0)

engine/include/sophia/util/delegate.hpp

@@ -2,13 +2,12 @@
 
 #include <functional>
 #include <memory>
+#include <sophia/util/logger.hpp>
 #include <stdexcept>
 #include <string>
 #include <typeinfo>
 #include <vector>
 
-#include <sophia/util/logger.hpp>
-
 #define DEFAULT_DELEGATE_FUNCTOR_ALLOC 5
 
 namespace sophia {
@@ -39,7 +38,9 @@ class expired_weak_object : public std::runtime_error {
 template <class O, typename... A>
 std::function<void(A...)> createWeakFunction(void (O::*method)(A...),
                                              std::shared_ptr<O> obj) {
-  if (!obj) { throw std::invalid_argument("method and obj must not be null"); }
+  if (!obj) {
+    throw std::invalid_argument("method and obj must not be null");
+  }
 
   std::weak_ptr<O> weakObj = obj;
 
@@ -82,7 +83,7 @@ class Delegate {
         try {
           this->functors[i](std::forward<A>(args)...);
         } catch (const expired_weak_object& e) {
-          log::error("delegate invoke error: ", e.what());
+          log::error("delegate invoke error: {}", e.what());
           deadFunctorIndexs.push_back(i);
         }
       }
@@ -97,7 +98,9 @@ class Delegate {
   void operator=(Functor c) {
     clear();
 
-    if (c != nullptr) { add(c); }
+    if (c != nullptr) {
+      add(c);
+    }
   }
 
   void operator+=(Functor c) { add(c); }

engine/include/sophia/util/logger.hpp

@@ -1,23 +1,36 @@
 /**
- * Lots of work still needs to be done in here.
+ * std::format-style logging. Format strings are checked at compile time.
  *
  * Usage:
  * using namespace sophia;
- * log::fatal("fatal message")
+ * log::fatal("failed to load {}", path)
- * log::info("Infomation message")
+ * log::info("loaded {} meshes in {:.2f}ms", count, ms)
+ * log::debug("value: {}", x)  // prefixed with file:line
+ * log::print("no prefix, just the message")
+ *
+ * Everything is compiled out in release (NDEBUG) builds.
  *
  * TODO Impl some form of log error handling
  */
 
 #pragma once
 
-#include <iostream>
+#include <cstdio>
+#include <format>
+#include <print>
+#include <source_location>
+#include <string_view>
+#include <type_traits>
 #include <utility>
 
-#include <sophia/types.hpp>
-
 namespace sophia::log {
 
+#ifndef NDEBUG
+inline constexpr bool enabled = true;
+#else
+inline constexpr bool enabled = false;
+#endif  // !NDEBUG
+
 enum class LEVEL {
   NONE,
   FATAL,
@@ -29,98 +42,113 @@ enum class LEVEL {
   TRACE,
 };
 
-// Helper print functions
+namespace detail {
-#define LOG_PRINT_HELPER(MSG) std::cout << MSG
-#define LOG_PREFIX_FATAL LOG_PRINT_HELPER("\033[1;91m[FATAL]\033[0m ")
-#define LOG_PREFIX_ERROR LOG_PRINT_HELPER("\033[1;31m[ERROR]\033[0m ")
-#define LOG_PREFIX_WARNING LOG_PRINT_HELPER("\033[1;33m[WARNING]\033[0m ")
-#define LOG_PREFIX_INFO LOG_PRINT_HELPER("\033[32m[INFO]\033[0m ")
-#define LOG_PREFIX_VERBOSE LOG_PRINT_HELPER("\033[36m[VERBOSE]\033[0m ")
-#define LOG_PREFIX_DEBUG LOG_PRINT_HELPER("\033[1;34m[DEBUG]\033[0m ")
-#define LOG_PREFIX_TRACE LOG_PRINT_HELPER("\033[1;90m[TRACE]\033[0m ")
 
-template <typename... Args>
+constexpr std::string_view prefix(LEVEL level) {
-void log(LEVEL level = LEVEL::NONE, Args... args) {
-#ifndef NDEBUG
   switch (level) {
     case LEVEL::FATAL:
-      LOG_PREFIX_FATAL;
+      return "\033[1;91m[FATAL]\033[0m ";
-      break;
     case LEVEL::ERROR:
-      LOG_PREFIX_ERROR;
+      return "\033[1;31m[ERROR]\033[0m ";
-      break;
     case LEVEL::WARNING:
-      LOG_PREFIX_WARNING;
+      return "\033[1;33m[WARNING]\033[0m ";
-      break;
     case LEVEL::INFO:
-      LOG_PREFIX_INFO;
+      return "\033[32m[INFO]\033[0m ";
-      break;
     case LEVEL::VERBOSE:
-      LOG_PREFIX_VERBOSE;
+      return "\033[36m[VERBOSE]\033[0m ";
-      break;
+    case LEVEL::DEBUGGING:
-    // case LEVEL::DEBUGGING:
+      return "\033[1;34m[DEBUG]\033[0m ";
-    //     LOG_PREFIX_DEBUG;
-    //     break;
     case LEVEL::TRACE:
-      LOG_PREFIX_TRACE;
+      return "\033[1;90m[TRACE]\033[0m ";
-      break;
     default:
-      std::cout << "\033[1;90m[LOG]\033[0m ";
+      return "\033[1;90m[LOG]\033[0m ";
-      break;
   }
+}
 
-  ((std::cout << ' ' << std::forward<Args>(args)), ...);
+inline void write(std::string_view prefix, std::string_view message) {
-  std::cout << std::endl;
+  std::println(stdout, "{}{}", prefix, message);
-#else
+  std::fflush(stdout);
-  (void)level;
+}
-  (void)std::initializer_list<int>{((void)args, 0)...};
+
-#endif  // !NDEBUG
+// Captures the caller's location alongside the format string, since a
+// defaulted std::source_location parameter can't follow a parameter pack.
+template <typename... Args>
+struct FormatWithLocation {
+  std::format_string<Args...> fmt;
+  std::source_location location;
+
+  template <typename S>
+    requires std::is_convertible_v<const S&, std::string_view>
+  consteval FormatWithLocation(
+      const S& fmt,
+      std::source_location location = std::source_location::current())
+      : fmt(fmt), location(location) {}
+};
+
+}  // namespace detail
+
+template <typename... Args>
+void log(LEVEL level, std::format_string<Args...> fmt, Args&&... args) {
+  if constexpr (enabled) {
+    detail::write(detail::prefix(level),
+                  std::format(fmt, std::forward<Args>(args)...));
+  }
 }
 
 template <typename... Args>
-void fatal(Args... args) {
+void fatal(std::format_string<Args...> fmt, Args&&... args) {
-  log(LEVEL::FATAL, args...);
+  log(LEVEL::FATAL, fmt, std::forward<Args>(args)...);
 }
 
 template <typename... Args>
-void error(Args... args) {
+void error(std::format_string<Args...> fmt, Args&&... args) {
-  log(LEVEL::ERROR, args...);
+  log(LEVEL::ERROR, fmt, std::forward<Args>(args)...);
 }
 
 template <typename... Args>
-void warning(Args... args) {
+void warning(std::format_string<Args...> fmt, Args&&... args) {
-  log(LEVEL::WARNING, args...);
+  log(LEVEL::WARNING, fmt, std::forward<Args>(args)...);
 }
 
 template <typename... Args>
-void info(Args... args) {
+void info(std::format_string<Args...> fmt, Args&&... args) {
-  log(LEVEL::INFO, args...);
+  log(LEVEL::INFO, fmt, std::forward<Args>(args)...);
 }
 
 template <typename... Args>
-void verbose(Args... args) {
+void verbose(std::format_string<Args...> fmt, Args&&... args) {
-  log(LEVEL::VERBOSE, args...);
+  log(LEVEL::VERBOSE, fmt, std::forward<Args>(args)...);
 }
 
 template <typename... Args>
-void debug(const char* file, u16 line, Args... args) {
+void debug(detail::FormatWithLocation<std::type_identity_t<Args>...> fmt,
-#ifndef NDEBUG
+           Args&&... args) {
-  LOG_PREFIX_DEBUG;
+  if constexpr (enabled) {
-  std::cout << file << "::" << line;
+    detail::write(
-  ((std::cout << ' ' << std::forward<Args>(args)), ...);
+        detail::prefix(LEVEL::DEBUGGING),
-  std::cout << std::endl;
+        std::format("{}:{} {}", fmt.location.file_name(), fmt.location.line(),
-#else
+                    std::format(fmt.fmt, std::forward<Args>(args)...)));
-  (void)file;
+  }
-  (void)line;
-  (void)std::initializer_list<int>{((void)args, 0)...};
-#endif  // !NDEBUG
 }
-// trick
-#define debug(...) debug(__FILE__, __LINE__, __VA_ARGS__)
 
 template <typename... Args>
-void trace(Args... args) {
+void trace(std::format_string<Args...> fmt, Args&&... args) {
-  log(LEVEL::TRACE, args...);
+  log(LEVEL::TRACE, fmt, std::forward<Args>(args)...);
+}
+
+// Like the functions above, but with no "[LEVEL]" prefix. With no arguments,
+// an empty line.
+inline void print() {
+  if constexpr (enabled) {
+    detail::write("", "");
+  }
+}
+
+template <typename... Args>
+void print(std::format_string<Args...> fmt, Args&&... args) {
+  if constexpr (enabled) {
+    detail::write("", std::format(fmt, std::forward<Args>(args)...));
+  }
 }
 
 }  // namespace sophia::log

engine/include/sophia/util/pool.hpp

@@ -0,0 +1,128 @@
+#pragma once
+
+#include <memory>
+#include <sophia/handles.hpp>
+#include <sophia/types.hpp>
+#include <sophia/util/assert.hpp>
+#include <utility>
+#include <vector>
+
+namespace sophia {
+
+template <typename T>
+class Pool {
+ public:
+  explicit Pool(const char* name) : name{name} {}
+
+  Pool(const Pool&) = delete;
+  Pool& operator=(const Pool&) = delete;
+
+  template <typename... Args>
+  Handle<T> create(Args&&... args) {
+    return add(std::make_unique<T>(std::forward<Args>(args)...));
+  }
+
+  Handle<T> add(std::unique_ptr<T> item) {
+    if (!freeList.empty()) {
+      u32 index = freeList.back();
+      freeList.pop_back();
+      slots[index].item = std::move(item);
+      return Handle<T>{index, slots[index].generation};
+    }
+
+    slots.push_back(Slot{std::move(item), 0});
+    return Handle<T>{static_cast<u32>(slots.size() - 1), 0};
+  }
+
+  T& get(Handle<T> handle) {
+    return const_cast<T&>(std::as_const(*this).get(handle));
+  }
+
+  const T& get(Handle<T> handle) const { return *validate(handle).item; }
+
+  void release(Handle<T> handle) {
+    validate(handle);
+
+    Slot& slot = slots[handle.index];
+    slot.item.reset();
+    slot.generation = (slot.generation + 1) & GENERATION_MASK;
+    freeList.push_back(handle.index);
+  }
+
+  bool isAlive(Handle<T> handle) const {
+    return handle.isValid() && handle.index < slots.size() &&
+           slots[handle.index].generation == handle.generation &&
+           slots[handle.index].item != nullptr;
+  }
+
+  u32 size() const { return static_cast<u32>(slots.size() - freeList.size()); }
+
+  template <typename Fn>
+  void forEach(Fn&& fn) {
+    for (Slot& slot : slots) {
+      if (slot.item) {
+        fn(*slot.item);
+      }
+    }
+  }
+
+  template <typename Fn>
+  void forEach(Fn&& fn) const {
+    for (const Slot& slot : slots) {
+      if (slot.item) {
+        fn(*slot.item);
+      }
+    }
+  }
+
+  /** Calls `fn(handle, item)` for every live item. */
+  template <typename Fn>
+  void forEachWithHandle(Fn&& fn) const {
+    for (u32 index = 0; index < slots.size(); index++) {
+      const Slot& slot = slots[index];
+      if (slot.item) {
+        fn(Handle<T>{index, slot.generation}, *slot.item);
+      }
+    }
+  }
+
+  template <typename Predicate>
+  T* findIf(Predicate&& predicate) {
+    return const_cast<T*>(
+        std::as_const(*this).findIf(std::forward<Predicate>(predicate)));
+  }
+
+  template <typename Predicate>
+  const T* findIf(Predicate&& predicate) const {
+    for (const Slot& slot : slots) {
+      if (slot.item && predicate(*slot.item)) {
+        return slot.item.get();
+      }
+    }
+    return nullptr;
+  }
+
+ private:
+  static constexpr u32 GENERATION_MASK = (1u << 12) - 1;
+
+  struct Slot {
+    std::unique_ptr<T> item;
+    u32 generation = 0;
+  };
+
+  const Slot& validate(Handle<T> handle) const {
+    SOPHIA_ASSERT(handle.isValid(), "invalid handle: {}", name);
+    SOPHIA_ASSERT(handle.index < slots.size(), "{} handle index out of range: {}", name, static_cast<u32>(handle.index));
+
+    const Slot& slot = slots[handle.index];
+    SOPHIA_ASSERT(slot.generation == handle.generation, "stale {} handle (generation mismatch): {}", name, static_cast<u32>(handle.index));
+    SOPHIA_ASSERT(slot.item != nullptr, "{} handle refers to a released item: {}", name, static_cast<u32>(handle.index));
+    return slot;
+  }
+
+  const char* name;
+  std::vector<Slot> slots;
+  std::vector<u32> freeList;
+};
+
+}  // namespace sophia

engine/src/application.cpp

@@ -1,46 +1,48 @@
+#include <imgui.h>
+
+#include <algorithm>
 #include <array>
 #include <chrono>
 #include <cstddef>
+#include <glm/glm.hpp>
+#include <glm/gtc/matrix_transform.hpp>
+#include <map>
+#include <optional>
+#include <set>
 #include <sophia/application.hpp>
 #include <sophia/util/logger.hpp>
 #include <string>
+#include <tracy/Tracy.hpp>
 #include <utility>
 #include <vector>
 #include <vulkan/vulkan.hpp>
 
-#define GLM_FORCE_RADIANS
+#include "renderer/imgui_renderer.hpp"
-#define GLM_FORCE_DEPTH_ZERO_TO_ONE
+#include "renderer/model_render_system.hpp"
-#include <imgui.h>
+#include "renderer/render_context.hpp"
-
+#include "renderer/render_graph.hpp"
-#include <glm/glm.hpp>
+#include "renderer/scene_renderer.hpp"
-
+#include "resources/mesh.hpp"
-#include "buffer.hpp"
+#include "resources/render_target.hpp"
-#include "device.hpp"
+#include "resources/resource_registry.hpp"
-#include "imgui_renderer.hpp"
+#include "vulkan/buffer.hpp"
-#include "mesh.hpp"
+#include "vulkan/device.hpp"
-#include "pipelines/graphics_pipeline.hpp"
+#include "vulkan/pipelines/graphics_pipeline.hpp"
-#include "render_context.hpp"
+#include "vulkan/shader.hpp"
-#include "shader.hpp"
-#include "systems/model_render_system.hpp"
 #include "window.hpp"
 
 namespace sophia {
 
 namespace {
 
-struct Vertex {
-  glm::vec2 position;
-  glm::vec3 color;
-};
-
-struct PushConstants {
-  glm::mat4 transform;
-  glm::vec4 color;
-  glm::vec4 data;
-};
-
 std::vector<std::string> commandLineArgs;
 
+constexpr ClearColor CLEAR_COLOR = {0.01f, 0.01f, 0.02f, 1.0f};
+
+bool hasFlag(ClearFlags flags, ClearFlags flag) {
+  return (static_cast<u8>(flags) & static_cast<u8>(flag)) != 0;
+}
+
 }  // namespace
 
 class Application::Impl {
@@ -50,15 +52,41 @@ class Application::Impl {
         config{config},
         window{config.width, config.height, config.name},
         device{&window},
-        renderContext{window, device} {}
+        renderContext{window, device},
+        resourceRegistry{device, renderContext.getImageFormat()} {}
 
   void run() {
     ModelRenderSystem modelRenderSystem{device, renderContext};
+    SceneRenderer sceneRenderer{this->application.sceneRegistry,
+                                this->resourceRegistry, device,
+                                renderContext.getImageFormat()};
     ImGuiRenderer imguiRenderer{window, device, renderContext.getImageFormat(),
-                                renderContext.getImageCount()};
+                                renderContext.getImageCount(),
+                                this->resourceRegistry};
+    this->application._ui.renderer = &imguiRenderer;
+
+    this->application.consoleCommandRegistry.registerCommand(
+        "reset_layout", "Restore the default panel layout",
+        [&imguiRenderer](const std::vector<std::string>&) {
+          imguiRenderer.resetLayout();
+          return std::string{"Layout reset"};
+        });
 
     this->application.onCreate();
 
+    auto& meshPool = this->resourceRegistry.meshPool;
+    auto& renderTargetPool = this->resourceRegistry.renderTargetPool;
+
+    PanelRegistry& panelRegistry = this->application.panelRegistry;
+    SceneRegistry& sceneRegistry = this->application.sceneRegistry;
+    SceneViewRegistry& sceneViewRegistry = this->application.sceneViewRegistry;
+
+    imguiRenderer.setDefaultLayout(panelRegistry.getDefaultLayout());
+
+    // Views already warned about, so each warns once.
+    std::set<SceneViewHandle> viewsWithoutCamera;
+    std::set<SceneViewHandle> viewsOverwritingOthers;
+
     auto startTime = std::chrono::high_resolution_clock::now();
     auto currentTime = startTime;
     u32 frameIndex = 0;
@@ -74,17 +102,27 @@ class Application::Impl {
       double elapsedTime =
           std::chrono::duration<double>(currentTime - startTime).count();
 
+      // Resizing waits for the GPU, so it has to happen before any of this
+      // frame's work (or ImGui's references to the targets) is recorded.
+      renderTargetPool.applyPendingResizes();
+
       vk::Extent2D extent = renderContext.getExtent();
       FrameInfo frameInfo{frameIndex, elapsedTime, deltaTime,
                           glm::vec2(static_cast<float>(extent.width),
-                                    static_cast<float>(extent.height)),
+                                    static_cast<float>(extent.height))};
-                          this->application.camera};
+      {
-      this->application.onUpdate(frameInfo);
+        ZoneScopedN("Application::onUpdate");
-      this->application.camera.setProjection(
+        this->application.onUpdate(frameInfo);
-          -frameInfo.currentFramebufferExtent.x / 2.f,
+      }
-          frameInfo.currentFramebufferExtent.x / 2.f,
+
-          -frameInfo.currentFramebufferExtent.y / 2.f,
+      // Canvas draws in window pixels, origin at the center.
-          frameInfo.currentFramebufferExtent.y / 2.f);
+      // TODO: replace with Debug/Gizmos drawn into scene views through their
+      // cameras.
+      glm::mat4 canvasProjection =
+          glm::ortho(-frameInfo.currentFramebufferExtent.x / 2.f,
+                     frameInfo.currentFramebufferExtent.x / 2.f,
+                     -frameInfo.currentFramebufferExtent.y / 2.f,
+                     frameInfo.currentFramebufferExtent.y / 2.f);
 
       vk::CommandBuffer commandBuffer = renderContext.beginFrame();
       if (!commandBuffer) {
@@ -92,41 +130,13 @@ class Application::Impl {
       }
 
       imguiRenderer.beginFrame();
+      sceneRenderer.beginFrame(renderContext.getFrameIndex());
 
-      this->application.panelRegistry.update(frameInfo);
+      panelRegistry.update(frameInfo);
-      this->application.onRender();
+      {
-
+        ZoneScopedN("Application::onRender");
-      renderContext.transitionCurrentImage(
+        this->application.onRender();
-          commandBuffer, vk::ImageLayout::eColorAttachmentOptimal);
+      }
-
-      vk::ClearValue clearValue{};
-      clearValue.color =
-          vk::ClearColorValue{std::array<float, 4>{0.01f, 0.01f, 0.02f, 1.0f}};
-
-      vk::RenderingAttachmentInfo colorAttachment{};
-      colorAttachment.imageView = renderContext.getCurrentImageView();
-      colorAttachment.imageLayout = vk::ImageLayout::eColorAttachmentOptimal;
-      colorAttachment.loadOp = vk::AttachmentLoadOp::eClear;
-      colorAttachment.storeOp = vk::AttachmentStoreOp::eStore;
-      colorAttachment.clearValue = clearValue;
-
-      vk::RenderingInfo renderingInfo{};
-      renderingInfo.renderArea = vk::Rect2D{{0, 0}, extent};
-      renderingInfo.layerCount = 1;
-      renderingInfo.colorAttachmentCount = 1;
-      renderingInfo.pColorAttachments = &colorAttachment;
-
-      commandBuffer.beginRendering(renderingInfo);
-
-      vk::Viewport viewport{0.0f,
-                            0.0f,
-                            static_cast<float>(extent.width),
-                            static_cast<float>(extent.height),
-                            0.0f,
-                            1.0f};
-      vk::Rect2D scissor{{0, 0}, extent};
-      commandBuffer.setViewport(0, viewport);
-      commandBuffer.setScissor(0, scissor);
 
       std::vector<ModelRenderSystem::MeshInstance> instances;
       instances.reserve(this->meshes.size() + this->drawCalls.size());
@@ -135,18 +145,124 @@ class Application::Impl {
       }
       instances.insert(instances.end(), this->drawCalls.begin(),
                        this->drawCalls.end());
-
-      modelRenderSystem.render(commandBuffer, instances, frameInfo);
       this->drawCalls.clear();
 
-      imguiRenderer.endFrame(commandBuffer);
+      RenderGraph graph{renderContext.getTracyContext()};
+      ImageRef backbuffer =
+          graph.importImage(renderContext.getCurrentImage(), Access::Present);
 
-      commandBuffer.endRendering();
+      struct ViewTarget {
+        ImageRef color;
+        ImageRef depth;
+      };
+      std::map<RenderTargetHandle, ViewTarget> viewTargets;
+      // Views without a target render straight into the backbuffer.
+      std::optional<ViewTarget> swapchainTarget;
+      for (SceneViewHandle handle : sceneViewRegistry.GetRenderQueue()) {
+        const SceneView& view = sceneViewRegistry.peek(handle);
+        bool toSwapchain = !view.target.isValid();
+        if (!sceneRegistry.isAlive(view.scene) ||
+            !sceneRegistry.get(view.scene).isVisible() ||
+            (!toSwapchain && !renderTargetPool.isAlive(view.target))) {
+          continue;
+        }
 
-      renderContext.transitionCurrentImage(commandBuffer,
+        ViewTarget target;
-                                           vk::ImageLayout::ePresentSrcKHR);
+        vk::Extent2D targetExtent;
+        // Whether this is the first view this frame to render to its target.
+        bool firstOnTarget = false;
+        if (toSwapchain) {
+          firstOnTarget = !swapchainTarget;
+          if (!swapchainTarget) {
+            swapchainTarget = {
+                backbuffer,
+                graph.importImage(renderContext.getCurrentDepthImage(),
+                                  Access::DepthWrite)};
+          }
+          target = *swapchainTarget;
+          targetExtent = renderContext.getExtent();
+        } else {
+          RenderTarget& renderTarget = renderTargetPool.get(view.target);
+          auto [it, inserted] = viewTargets.try_emplace(view.target);
+          firstOnTarget = inserted;
+          if (inserted) {
+            it->second = {
+                graph.importImage(renderTarget.getImage(), Access::SampledRead),
+                graph.importImage(renderTarget.getDepthImage(),
+                                  Access::DepthWrite)};
+          }
+          target = it->second;
+          targetExtent = renderTarget.getExtent();
+        }
+
+        if (!firstOnTarget && hasFlag(view.clearFlags, ClearFlags::Color) &&
+            viewsOverwritingOthers.insert(handle).second) {
+          log::warning(
+              "scene view clears its target after another view already "
+              "rendered to it this frame, hiding that view (give it clearFlags "
+              "without Color, or render it first with a lower priority)");
+        }
+
+        const vec4& color = view.clearColor;
+        graph.addPass(
+            "scene view " + std::to_string(handle.index),
+            [&](RenderGraph::PassBuilder& pass) {
+              pass.writeColor(target.color,
+                              hasFlag(view.clearFlags, ClearFlags::Color)
+                                  ? vk::AttachmentLoadOp::eClear
+                                  : vk::AttachmentLoadOp::eLoad,
+                              {color.r, color.g, color.b, color.a});
+              pass.writeDepth(target.depth,
+                              hasFlag(view.clearFlags, ClearFlags::Depth)
+                                  ? vk::AttachmentLoadOp::eClear
+                                  : vk::AttachmentLoadOp::eLoad);
+            },
+            [&sceneRenderer, &sceneRegistry, &sceneViewRegistry,
+             &viewsWithoutCamera, handle,
+             targetExtent](vk::CommandBuffer commandBuffer) {
+              ZoneScopedN("scene view pass");
+              const SceneView& view = sceneViewRegistry.peek(handle);
+              Entity camera =
+                  view.camera ? view.camera
+                              : sceneRegistry.get(view.scene).getActiveCamera();
+              // No camera to look through: the target is just cleared.
+              if (!camera) {
+                if (viewsWithoutCamera.insert(handle).second) {
+                  log::warning(
+                      "scene view has no camera and its scene has no active "
+                      "camera; it will only be cleared (see "
+                      "Scene::createCamera)");
+                }
+                return;
+              }
+              sceneRenderer.render(commandBuffer, view, camera, targetExtent);
+            });
+      }
+
+      graph.addPass(
+          "main",
+          [&](RenderGraph::PassBuilder& pass) {
+            // Keep what scene views drew into the backbuffer.
+            pass.writeColor(backbuffer,
+                            swapchainTarget ? vk::AttachmentLoadOp::eLoad
+                                            : vk::AttachmentLoadOp::eClear,
+                            CLEAR_COLOR);
+            for (const auto& [handle, target] : viewTargets) {
+              pass.sample(target.color);
+            }
+          },
+          [&](vk::CommandBuffer commandBuffer) {
+            ZoneScopedN("main pass");
+            modelRenderSystem.render(commandBuffer, instances,
+                                     canvasProjection);
+
+            imguiRenderer.endFrame(commandBuffer);
+          });
+
+      graph.execute(commandBuffer);
 
       renderContext.endFrame();
+      FrameMark;
 
       frameIndex++;
     }
@@ -155,21 +271,24 @@ class Application::Impl {
 
     device.waitIdle();
 
+    this->application._ui.renderer = nullptr;
+
     auto endTime = std::chrono::high_resolution_clock::now();
     double totalRuntime =
         std::chrono::duration<double>(endTime - startTime).count();
-    log::info("Application ran for", totalRuntime, "s");
+    log::info("Application ran for {:.2f}s", totalRuntime);
   }
 
   void pushMesh(std::vector<CanvasVertex> vertices, std::vector<u32> indices) {
-    Mesh::Builder builder{};
+    MeshData data;
-    builder.vertices.reserve(vertices.size());
+    data.vertices.reserve(vertices.size());
     for (const CanvasVertex& vertex : vertices) {
-      builder.vertices.push_back({vertex.position, vertex.color});
+      data.vertices.push_back(
+          {.position = {vertex.position, 0.f}, .color = {vertex.color, 1.f}});
     }
-    builder.indices = std::move(indices);
+    data.indices = std::move(indices);
 
-    this->meshes.push_back(std::make_unique<Mesh>(this->device, builder));
+    this->meshes.push_back(std::make_unique<Mesh>(this->device, data));
   }
 
   void clearMeshes() {
@@ -184,7 +303,7 @@ class Application::Impl {
     this->drawCalls.push_back({&mesh, transform});
   }
 
-  Device& getDevice() { return device; }
+  ResourceRegistry& getResourceRegistry() { return resourceRegistry; }
 
  private:
   Application& application;
@@ -192,6 +311,7 @@ class Application::Impl {
   Window window;
   Device device;
   RenderContext renderContext;
+  ResourceRegistry resourceRegistry;
 
   std::vector<std::unique_ptr<Mesh>> meshes;
   std::vector<ModelRenderSystem::MeshInstance> drawCalls;
@@ -205,13 +325,17 @@ Application::Application(const Config& config)
     : impl{std::make_unique<Impl>(*this, config)},
       canvas{this},
       args{std::move(commandLineArgs)},
-      assetRegistry{impl->getDevice()},
+      _ui{ResourceRegistryRef{impl->getResourceRegistry()}},
-      _debugUI{this->panelRegistry} {}
+      _debugUI{this->panelRegistry, this->consoleCommandRegistry} {}
 
 Application::~Application() = default;
 
 void Application::run() { impl->run(); }
 
+ResourceRegistryRef Application::resources() {
+  return ResourceRegistryRef{impl->getResourceRegistry()};
+}
+
 void Application::pushMesh(std::vector<CanvasVertex> vertices,
                            std::vector<u32> indices) {
   impl->pushMesh(std::move(vertices), std::move(indices));
@@ -220,7 +344,7 @@ void Application::pushMesh(std::vector<CanvasVertex> vertices,
 void Application::clearMeshes() { impl->clearMeshes(); }
 
 void Application::drawMesh(MeshHandle handle, const glm::mat4& transform) {
-  impl->drawMesh(assetRegistry.get<Mesh>(handle), transform);
+  impl->drawMesh(impl->getResourceRegistry().meshPool.get(handle), transform);
 }
 
 }  // namespace sophia

engine/src/assets/asset_registry.cpp

@@ -1,60 +0,0 @@
-#include <sophia/asset_registry.hpp>
-#include <sophia/util/assert.hpp>
-
-#include "mesh.hpp"
-#include "pools/mesh_pool.hpp"
-
-namespace sophia {
-
-class AssetRegistry::Impl {
- public:
-  explicit Impl(Device& device) : meshPool{device} {}
-
-  MeshPool meshPool;
-  // TexturePool texturePool;
-  // MaterialPool materialPool;
-};
-
-AssetRegistry::AssetRegistry(Device& device)
-    : impl{std::make_unique<Impl>(device)} {}
-
-AssetRegistry::~AssetRegistry() = default;
-
-template <>
-MeshHandle AssetRegistry::load<Mesh>(const std::string& path) {
-  (void)path;
-  SOPHIA_ASSERT(false,
-                "Mesh::load(path) is not implemented yet - no model file "
-                "format is supported; build one via Mesh::Builder for now");
-  return MeshHandle{};
-}
-
-template <typename T>
-typename AssetTraits<T>::Handle load(const std::string&) {
-  static_assert(sizeof(T) == 0,
-                "load<T> is not implemented for this asset type");
-}
-
-template <>
-void AssetRegistry::release<Mesh>(MeshHandle handle) {
-  impl->meshPool.release(handle);
-}
-
-template <>
-const Mesh& AssetRegistry::get<Mesh>(MeshHandle handle) const {
-  return impl->meshPool.get(handle);
-}
-
-MeshHandle AssetRegistry::loadMesh(std::vector<CanvasVertex> vertices,
-                                   std::vector<u32> indices) {
-  Mesh::Builder builder{};
-  builder.vertices.reserve(vertices.size());
-  for (const CanvasVertex& vertex : vertices) {
-    builder.vertices.push_back({vertex.position, vertex.color});
-  }
-  builder.indices = std::move(indices);
-
-  return impl->meshPool.create(builder);
-}
-
-}  // namespace sophia

engine/src/assets/pools/mesh_pool.cpp

@@ -1,58 +0,0 @@
-#include "assets/pools/mesh_pool.hpp"
-
-#include <sophia/util/assert.hpp>
-
-namespace sophia {
-
-namespace {
-constexpr u32 GENERATION_MASK = (1u << 12) - 1;
-}  // namespace
-
-MeshPool::MeshPool(Device& device) : device{device} {}
-
-MeshPool::~MeshPool() = default;
-
-MeshHandle MeshPool::create(const Mesh::Builder& builder) {
-  auto mesh = std::make_unique<Mesh>(device, builder);
-
-  if (!freeList.empty()) {
-    u32 index = freeList.back();
-    freeList.pop_back();
-    slots[index].mesh = std::move(mesh);
-    return MeshHandle{index, slots[index].generation};
-  }
-
-  slots.push_back(Slot{std::move(mesh), 0});
-  return MeshHandle{static_cast<u32>(slots.size() - 1), 0};
-}
-
-const Mesh& MeshPool::get(MeshHandle handle) const {
-  SOPHIA_ASSERT(handle.isValid(), "invalid MeshHandle");
-  SOPHIA_ASSERT(handle.index < slots.size(),
-                "MeshHandle index out of range:", handle.index);
-
-  const Slot& slot = slots[handle.index];
-  SOPHIA_ASSERT(slot.generation == handle.generation,
-                "stale MeshHandle (generation mismatch):", handle.index);
-  SOPHIA_ASSERT(slot.mesh != nullptr,
-                "MeshHandle refers to a released mesh:", handle.index);
-  return *slot.mesh;
-}
-
-void MeshPool::release(MeshHandle handle) {
-  SOPHIA_ASSERT(handle.isValid(), "invalid MeshHandle");
-  SOPHIA_ASSERT(handle.index < slots.size(),
-                "MeshHandle index out of range:", handle.index);
-
-  Slot& slot = slots[handle.index];
-  SOPHIA_ASSERT(slot.generation == handle.generation,
-                "stale MeshHandle (generation mismatch):", handle.index);
-  SOPHIA_ASSERT(slot.mesh != nullptr,
-                "MeshHandle already released:", handle.index);
-
-  slot.mesh.reset();
-  slot.generation = (slot.generation + 1) & GENERATION_MASK;
-  freeList.push_back(handle.index);
-}
-
-}  // namespace sophia

engine/src/assets/pools/mesh_pool.hpp

@@ -1,35 +0,0 @@
-#pragma once
-
-#include <memory>
-#include <vector>
-
-#include "device.hpp"
-#include "mesh.hpp"
-
-namespace sophia {
-
-class MeshPool {
- public:
-  explicit MeshPool(Device& device);
-  ~MeshPool();
-
-  MeshPool(const MeshPool&) = delete;
-  MeshPool& operator=(const MeshPool&) = delete;
-
-  MeshHandle create(const Mesh::Builder& builder);
-  const Mesh& get(MeshHandle handle) const;
-  void release(MeshHandle handle);
-
- private:
-  struct Slot {
-    std::unique_ptr<Mesh> mesh;
-    u32 generation = 0;
-  };
-
-  Device& device;
-
-  std::vector<Slot> slots;
-  std::vector<u32> freeList;
-};
-
-}  // namespace sophia

engine/src/console/console_command_registry.cpp

@@ -0,0 +1,31 @@
+#include <sophia/console/console_command_registry.hpp>
+
+namespace sophia {
+
+void ConsoleCommandRegistry::registerCommand(std::string name, std::string help,
+                                             Handler handler) {
+  commands[std::move(name)] = Command{std::move(help), std::move(handler)};
+}
+
+bool ConsoleCommandRegistry::dispatch(const std::string& name,
+                                      const std::vector<std::string>& args,
+                                      std::string& outResult) const {
+  auto it = commands.find(name);
+  if (it == commands.end()) {
+    return false;
+  }
+  outResult = it->second.handler(args);
+  return true;
+}
+
+std::vector<ConsoleCommandRegistry::CommandInfo> ConsoleCommandRegistry::list()
+    const {
+  std::vector<CommandInfo> result;
+  result.reserve(commands.size());
+  for (const auto& [name, command] : commands) {
+    result.push_back(CommandInfo{name, command.help});
+  }
+  return result;
+}
+
+}  // namespace sophia

engine/src/imgui_renderer.cpp

@@ -1,85 +0,0 @@
-#include "imgui_renderer.hpp"
-
-#include <imgui.h>
-#include <imgui_impl_glfw.h>
-#include <imgui_impl_vulkan.h>
-
-namespace sophia {
-
-ImGuiRenderer::ImGuiRenderer(Window& window, Device& device,
-                             vk::Format colorAttachmentFormat,
-                             u32 minImageCount) {
-  // 1. Construct ImGui context
-  IMGUI_CHECKVERSION();
-  ImGui::CreateContext();
-
-  ImGui_ImplGlfw_InitForVulkan(window.getGLFWwindow(), true);
-
-  ImGui_ImplVulkan_InitInfo initInfo = {};
-  device.populateImGuiInitInfo(initInfo);
-  initInfo.DescriptorPoolSize =
-      IMGUI_IMPL_VULKAN_MINIMUM_SAMPLED_IMAGE_POOL_SIZE + 5;
-  initInfo.MinImageCount = minImageCount;
-  initInfo.ImageCount = minImageCount;
-
-  VkFormat rawColorAttachmentFormat =
-      static_cast<VkFormat>(colorAttachmentFormat);
-  initInfo.UseDynamicRendering = true;
-  initInfo.PipelineInfoMain.PipelineRenderingCreateInfo.sType =
-      VK_STRUCTURE_TYPE_PIPELINE_RENDERING_CREATE_INFO_KHR;
-  initInfo.PipelineInfoMain.PipelineRenderingCreateInfo.colorAttachmentCount =
-      1;
-  initInfo.PipelineInfoMain.PipelineRenderingCreateInfo
-      .pColorAttachmentFormats = &rawColorAttachmentFormat;
-
-  ImGui_ImplVulkan_Init(&initInfo);
-
-  // 2. Enable dark theme
-  ImGui::StyleColorsDark();
-
-  // 3. Enable docking / keyboard
-  ImGuiIO& io = ImGui::GetIO();
-  io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;
-  io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;
-  io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;
-
-  /**
-   * When viewports are enabled we tweak WindowRounding/WindowBg so
-   * platform windows can look identical to regular ones.
-   */
-  ImGuiStyle& style = ImGui::GetStyle();
-  if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_ViewportsEnable) {
-    style.WindowRounding = 0.0f;
-    style.Colors[ImGuiCol_WindowBg].w = 1.0f;
-  }
-}
-
-ImGuiRenderer::~ImGuiRenderer() {
-  ImGui_ImplVulkan_Shutdown();
-  ImGui_ImplGlfw_Shutdown();
-  ImGui::DestroyContext();
-}
-
-void ImGuiRenderer::beginFrame() {
-  ImGui_ImplVulkan_NewFrame();
-  ImGui_ImplGlfw_NewFrame();
-  ImGui::NewFrame();
-
-  ImGui::DockSpaceOverViewport(0, ImGui::GetMainViewport(),
-                               ImGuiDockNodeFlags_PassthruCentralNode);
-}
-
-void ImGuiRenderer::endFrame(vk::CommandBuffer commandBuffer) {
-  ImGui::Render();
-  ImDrawData* mainDrawData = ImGui::GetDrawData();
-
-  ImGuiIO& io = ImGui::GetIO();
-  if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable) {
-    ImGui::UpdatePlatformWindows();
-    ImGui::RenderPlatformWindowsDefault();
-  }
-
-  ImGui_ImplVulkan_RenderDrawData(mainDrawData, commandBuffer);
-}
-
-}  // namespace sophia

engine/src/imgui_renderer.hpp

@@ -1,23 +0,0 @@
-#pragma once
-
-#include <sophia/types.hpp>
-
-#include "device.hpp"
-#include "window.hpp"
-
-namespace sophia {
-
-class ImGuiRenderer {
- public:
-  ImGuiRenderer(const ImGuiRenderer&) = delete;
-  ImGuiRenderer& operator=(const ImGuiRenderer&) = delete;
-
-  ImGuiRenderer(Window& window, Device& device,
-                vk::Format colorAttachmentFormat, u32 minImageCount);
-  ~ImGuiRenderer();
-
-  void beginFrame();
-  void endFrame(vk::CommandBuffer commandBuffer);
-};
-
-}  // namespace sophia

engine/src/mesh.hpp

@@ -1,70 +0,0 @@
-#pragma once
-
-#include <memory>
-#include <sophia/asset_registry.hpp>
-#include <sophia/types.hpp>
-#include <vector>
-
-#define GLM_FORCE_RADIANS
-#define GLM_FORCE_DEPTH_ZERO_TO_ONE
-#include <glm/glm.hpp>
-
-#include "buffer.hpp"
-#include "device.hpp"
-
-namespace sophia {
-
-class Mesh {
- public:
-  using HandleType = MeshHandle;
-
-  struct Vertex {
-    glm::vec2 position{};
-    glm::vec3 color{};
-    // glm::vec3 normal{};
-    // glm::vec2 uv{};
-
-    static std::vector<vk::VertexInputBindingDescription>
-    getBindingDescriptions();
-    static std::vector<vk::VertexInputAttributeDescription>
-    getAttributeDescriptions();
-
-    // bool operator==(const Vertex& other) const {
-    //   return position == other.position && color == other.color;
-    // }
-  };
-
-  struct Builder {
-    std::vector<Vertex> vertices{};
-    std::vector<uint32_t> indices{};
-
-    // void loadModel(const std::string& filepath);
-  };
-
-  Mesh(Device& device, const Mesh::Builder& builder);
-  ~Mesh();
-
-  Mesh(const Mesh&) = delete;
-  Mesh& operator=(const Mesh&) = delete;
-
-  // static std::unique_ptr<Mesh> createMeshFromFile(
-  //     Device& device, const std::string& filepath);
-
-  void bind(vk::CommandBuffer commandBuffer) const;
-  void draw(vk::CommandBuffer commandBuffer) const;
-
- private:
-  void createVertexBuffers(const std::vector<Vertex>& vertices);
-  void createIndexBuffers(const std::vector<u32>& indices);
-
-  Device& device;
-
-  std::unique_ptr<Buffer> vertexBuffer;
-  u32 vertexCount;
-
-  bool hasIndexBuffer = false;
-  std::unique_ptr<Buffer> indexBuffer;
-  u32 indexCount;
-};
-
-}  // namespace sophia

engine/src/renderer/imgui_renderer.cpp

@@ -0,0 +1,202 @@
+#include "renderer/imgui_renderer.hpp"
+
+#include <imgui.h>
+#include <imgui_impl_glfw.h>
+#include <imgui_impl_vulkan.h>
+#include <imgui_internal.h>
+
+#include <tracy/Tracy.hpp>
+
+#include "resources/render_target.hpp"
+
+namespace sophia {
+
+namespace {
+constexpr ImGuiDockNodeFlags DOCKSPACE_FLAGS =
+    ImGuiDockNodeFlags_PassthruCentralNode;
+
+void dockAll(const std::vector<std::string>& windows, ImGuiID nodeId) {
+  for (const std::string& name : windows) {
+    ImGui::DockBuilderDockWindow(name.c_str(), nodeId);
+  }
+}
+}  // namespace
+
+ImGuiRenderer::ImGuiRenderer(Window& window, Device& device,
+                             vk::Format colorAttachmentFormat,
+                             u32 minImageCount, ResourceRegistry& resources)
+    : resources{resources} {
+  // 1. Construct ImGui context
+  IMGUI_CHECKVERSION();
+  ImGui::CreateContext();
+
+  ImGui_ImplGlfw_InitForVulkan(window.getGLFWwindow(), true);
+
+  ImGui_ImplVulkan_InitInfo initInfo = {};
+  device.populateImGuiInitInfo(initInfo);
+  initInfo.DescriptorPoolSize =
+      IMGUI_IMPL_VULKAN_MINIMUM_SAMPLED_IMAGE_POOL_SIZE + 5;
+  initInfo.MinImageCount = minImageCount;
+  initInfo.ImageCount = minImageCount;
+
+  VkFormat rawColorAttachmentFormat =
+      static_cast<VkFormat>(colorAttachmentFormat);
+  initInfo.UseDynamicRendering = true;
+  initInfo.PipelineInfoMain.PipelineRenderingCreateInfo.sType =
+      VK_STRUCTURE_TYPE_PIPELINE_RENDERING_CREATE_INFO_KHR;
+  initInfo.PipelineInfoMain.PipelineRenderingCreateInfo.colorAttachmentCount =
+      1;
+  initInfo.PipelineInfoMain.PipelineRenderingCreateInfo
+      .pColorAttachmentFormats = &rawColorAttachmentFormat;
+
+  ImGui_ImplVulkan_Init(&initInfo);
+
+  // 2. Enable dark theme
+  ImGui::StyleColorsDark();
+
+  // 3. Enable docking / keyboard
+  ImGuiIO& io = ImGui::GetIO();
+  io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;
+  io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;
+  io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;
+
+  /**
+   * When viewports are enabled we tweak WindowRounding/WindowBg so
+   * platform windows can look identical to regular ones.
+   */
+  ImGuiStyle& style = ImGui::GetStyle();
+  if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_ViewportsEnable) {
+    style.WindowRounding = 0.0f;
+    style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+  }
+}
+
+ImGuiRenderer::~ImGuiRenderer() {
+  for (const auto& [index, texture] : textures) {
+    ImGui_ImplVulkan_RemoveTexture(texture.descriptorSet);
+  }
+  ImGui_ImplVulkan_Shutdown();
+  ImGui_ImplGlfw_Shutdown();
+  ImGui::DestroyContext();
+}
+
+void ImGuiRenderer::beginFrame() {
+  ZoneScoped;
+  releaseStaleTextures();
+
+  ImGui_ImplVulkan_NewFrame();
+  ImGui_ImplGlfw_NewFrame();
+  ImGui::NewFrame();
+
+  ImGuiID dockspaceId = ImGui::DockSpaceOverViewport(
+      0, ImGui::GetMainViewport(), DOCKSPACE_FLAGS);
+  applyLayoutIfNeeded(dockspaceId, DOCKSPACE_FLAGS);
+}
+
+ImTextureID ImGuiRenderer::getTextureId(RenderTargetHandle handle) {
+  const RenderTarget& target = resources.renderTargetPool.get(handle);
+  vk::ImageView view = target.getImage().getView();
+
+  auto it = textures.find(handle.index);
+  if (it != textures.end()) {
+    if (it->second.generation == handle.generation &&
+        it->second.version == target.getVersion()) {
+      return (ImTextureID)it->second.descriptorSet;
+    }
+    ImGui_ImplVulkan_RemoveTexture(it->second.descriptorSet);
+    textures.erase(it);
+  }
+
+  // ImGui owns the sampler; it only needs the view and the layout the image is
+  // left in once the scene pass has finished.
+  VkDescriptorSet descriptorSet = ImGui_ImplVulkan_AddTexture(
+      static_cast<VkImageView>(view), VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL);
+  textures[handle.index] = {handle.generation, target.getVersion(),
+                            descriptorSet};
+  return (ImTextureID)descriptorSet;
+}
+
+// Resizing and releasing a target both wait for the GPU before destroying its
+// image, so nothing in flight can still be using a stale texture.
+void ImGuiRenderer::releaseStaleTextures() {
+  for (auto it = textures.begin(); it != textures.end();) {
+    RenderTargetHandle handle{it->first, it->second.generation};
+    RenderTargetPool& renderTargetPool = resources.renderTargetPool;
+
+    bool stale =
+        !renderTargetPool.isAlive(handle) ||
+        renderTargetPool.get(handle).getVersion() != it->second.version;
+    if (stale) {
+      ImGui_ImplVulkan_RemoveTexture(it->second.descriptorSet);
+      it = textures.erase(it);
+    } else {
+      ++it;
+    }
+  }
+}
+
+void ImGuiRenderer::setDefaultLayout(DockLayout layout) {
+  defaultLayout = std::move(layout);
+  seedIfUnsaved = true;
+}
+
+void ImGuiRenderer::resetLayout() { forceReset = true; }
+
+void ImGuiRenderer::applyLayoutIfNeeded(ImGuiID dockspaceId,
+                                        ImGuiDockNodeFlags flags) {
+  if (defaultLayout.empty()) {
+    return;
+  }
+
+  bool apply = forceReset;
+  if (seedIfUnsaved) {
+    // A layout restored from imgui.ini shows up as a split root node.
+    ImGuiDockNode* root = ImGui::DockBuilderGetNode(dockspaceId);
+    apply = apply || root == nullptr || !root->IsSplitNode();
+    seedIfUnsaved = false;
+  }
+  if (!apply) {
+    return;
+  }
+  forceReset = false;
+
+  const ImVec2 size = ImGui::GetMainViewport()->Size;
+
+  ImGui::DockBuilderRemoveNode(dockspaceId);
+  ImGui::DockBuilderAddNode(dockspaceId, flags | ImGuiDockNodeFlags_DockSpace);
+  ImGui::DockBuilderSetNodeSize(dockspaceId, size);
+
+  ImGuiID center = dockspaceId;
+  const ImGuiID left = ImGui::DockBuilderSplitNode(
+      center, ImGuiDir_Left, defaultLayout.leftWidth, nullptr, &center);
+  // The right split is taken from what's left after the left split.
+  const float rightRatio =
+      defaultLayout.rightWidth / (1.0f - defaultLayout.leftWidth);
+  const ImGuiID right = ImGui::DockBuilderSplitNode(
+      center, ImGuiDir_Right, rightRatio, nullptr, &center);
+  const ImGuiID bottom = ImGui::DockBuilderSplitNode(
+      center, ImGuiDir_Down, defaultLayout.bottomHeight, nullptr, &center);
+
+  dockAll(defaultLayout.left, left);
+  dockAll(defaultLayout.right, right);
+  dockAll(defaultLayout.bottom, bottom);
+  dockAll(defaultLayout.center, center);
+
+  ImGui::DockBuilderFinish(dockspaceId);
+}
+
+void ImGuiRenderer::endFrame(vk::CommandBuffer commandBuffer) {
+  ZoneScoped;
+  ImGui::Render();
+  ImDrawData* mainDrawData = ImGui::GetDrawData();
+
+  ImGuiIO& io = ImGui::GetIO();
+  if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable) {
+    ImGui::UpdatePlatformWindows();
+    ImGui::RenderPlatformWindowsDefault();
+  }
+
+  ImGui_ImplVulkan_RenderDrawData(mainDrawData, commandBuffer);
+}
+
+}  // namespace sophia

engine/src/renderer/imgui_renderer.hpp

@@ -0,0 +1,54 @@
+#pragma once
+
+#include <imgui.h>
+
+#include <sophia/handles.hpp>
+#include <sophia/types.hpp>
+#include <sophia/ui/dock_layout.hpp>
+#include <unordered_map>
+
+#include "resources/resource_registry.hpp"
+#include "vulkan/device.hpp"
+#include "window.hpp"
+
+namespace sophia {
+
+class ImGuiRenderer {
+ public:
+  ImGuiRenderer(const ImGuiRenderer&) = delete;
+  ImGuiRenderer& operator=(const ImGuiRenderer&) = delete;
+
+  ImGuiRenderer(Window& window, Device& device,
+                vk::Format colorAttachmentFormat, u32 minImageCount,
+                ResourceRegistry& resources);
+  ~ImGuiRenderer();
+
+  void beginFrame();
+  void endFrame(vk::CommandBuffer commandBuffer);
+
+  ImTextureID getTextureId(RenderTargetHandle handle);
+
+  void setDefaultLayout(DockLayout layout);
+  void resetLayout();
+
+ private:
+  void applyLayoutIfNeeded(ImGuiID dockspaceId, ImGuiDockNodeFlags flags);
+  void releaseStaleTextures();
+
+  struct Texture {
+    u32 generation;
+    u32 version;
+    VkDescriptorSet descriptorSet;
+  };
+
+  ResourceRegistry& resources;
+
+  // Keyed by RenderTargetHandle::index.
+  std::unordered_map<u32, Texture> textures;
+
+  DockLayout defaultLayout;
+  bool seedIfUnsaved = false;
+  bool forceReset = false;
+};
+
+}  // namespace sophia

engine/src/renderer/mesh_render_system.cpp

@@ -0,0 +1,154 @@
+#include "renderer/mesh_render_system.hpp"
+
+#include <algorithm>
+#include <sophia/util/logger.hpp>
+#include <tracy/Tracy.hpp>
+
+#include "shaders/mesh.frag.spv.h"
+#include "shaders/mesh.vert.spv.h"
+
+namespace sophia {
+
+namespace {
+// Mesh::getAttributeDescriptions() takes locations below this.
+constexpr u32 FIRST_INSTANCE_LOCATION = 4;
+}  // namespace
+
+MeshRenderSystem::MeshRenderSystem(Device& device, vk::Format colorFormat,
+                                   vk::Format depthFormat,
+                                   ResourceRegistry& resources)
+    : device{device}, resources{resources} {
+  createPipelineLayout();
+  createPipeline(colorFormat, depthFormat);
+  createInstanceBuffers();
+}
+
+MeshRenderSystem::~MeshRenderSystem() {
+  log::trace("destroyed sophia::MeshRenderSystem");
+}
+
+void MeshRenderSystem::beginFrame(u32 frameIndex) {
+  this->frameIndex = frameIndex;
+  this->instanceCursor = 0;
+}
+
+void MeshRenderSystem::render(vk::CommandBuffer commandBuffer,
+                              const glm::mat4& viewProjection,
+                              std::span<const Instance> instances,
+                              std::span<const Batch> batches) {
+  ZoneScoped;
+  if (instances.empty()) {
+    return;
+  }
+
+  u32 available = MAX_INSTANCES_PER_FRAME - this->instanceCursor;
+  if (instances.size() > available) {
+    log::warning(
+        "MeshRenderSystem: frame instance buffer full, dropping {} meshes",
+        instances.size() - available);
+  }
+
+  Buffer& buffer = *this->instanceBuffers[this->frameIndex];
+  u32 base = this->instanceCursor;
+  u32 count = std::min(static_cast<u32>(instances.size()), available);
+  buffer.writeToBuffer(const_cast<Instance*>(instances.data()),
+                       count * sizeof(Instance), base * sizeof(Instance));
+  this->instanceCursor += count;
+
+  this->graphicsPipeline->bind(commandBuffer);
+
+  PushConstantData push{viewProjection};
+  commandBuffer.pushConstants(this->pipelineLayout.get(),
+                              vk::ShaderStageFlagBits::eVertex, 0,
+                              sizeof(PushConstantData), &push);
+
+  // Binding 1 stays bound across batches; each mesh rebinds binding 0.
+  vk::Buffer instanceBuffer = buffer.getBuffer();
+  vk::DeviceSize offset = 0;
+  commandBuffer.bindVertexBuffers(1, 1, &instanceBuffer, &offset);
+
+  for (const Batch& batch : batches) {
+    if (batch.firstInstance >= count) {
+      break;
+    }
+    u32 batchCount = std::min(batch.instanceCount, count - batch.firstInstance);
+
+    const Mesh& mesh = this->resources.meshPool.get(batch.mesh);
+    mesh.bind(commandBuffer);
+    mesh.draw(commandBuffer, batchCount, base + batch.firstInstance);
+  }
+}
+
+void MeshRenderSystem::createPipelineLayout() {
+  vk::PushConstantRange pushConstantRange{};
+  pushConstantRange.stageFlags = vk::ShaderStageFlagBits::eVertex;
+  pushConstantRange.offset = 0;
+  pushConstantRange.size = sizeof(PushConstantData);
+
+  vk::PipelineLayoutCreateInfo pipelineLayoutInfo = {};
+  pipelineLayoutInfo.setLayoutCount = 0;
+  pipelineLayoutInfo.pushConstantRangeCount = 1;
+  pipelineLayoutInfo.pPushConstantRanges = &pushConstantRange;
+
+  try {
+    this->pipelineLayout =
+        this->device.get()->createPipelineLayoutUnique(pipelineLayoutInfo);
+    log::trace("created vk::PipelineLayout");
+  } catch (const vk::SystemError& err) {
+    log::fatal("failed to create vk::PipelineLayout");
+    throw std::runtime_error("failed to create vk::PipelineLayout");
+  }
+}
+
+void MeshRenderSystem::createPipeline(vk::Format colorFormat,
+                                      vk::Format depthFormat) {
+  auto vertexShader = Shader::Builder()
+                          .fromSPIRV(shaders::mesh_vert_spv)
+                          .setStage(ShaderStage::VERTEX)
+                          .build();
+  auto fragmentShader = Shader::Builder()
+                            .fromSPIRV(shaders::mesh_frag_spv)
+                            .setStage(ShaderStage::FRAGMENT)
+                            .build();
+
+  std::vector<vk::VertexInputBindingDescription> bindings =
+      Mesh::getBindingDescriptions();
+  bindings.push_back({1, sizeof(Instance), vk::VertexInputRate::eInstance});
+
+  std::vector<vk::VertexInputAttributeDescription> attributes =
+      Mesh::getAttributeDescriptions();
+  // A mat4 attribute takes four consecutive locations, one per column.
+  for (u32 column = 0; column < 4; column++) {
+    attributes.push_back({FIRST_INSTANCE_LOCATION + column, 1,
+                          vk::Format::eR32G32B32A32Sfloat,
+                          static_cast<u32>(offsetof(Instance, model) +
+                                           column * sizeof(glm::vec4))});
+  }
+  attributes.push_back({FIRST_INSTANCE_LOCATION + 4, 1,
+                        vk::Format::eR32G32B32A32Sfloat,
+                        static_cast<u32>(offsetof(Instance, color))});
+
+  this->graphicsPipeline = GraphicsPipeline::Builder(this->device)
+                               .setVertexShader(*vertexShader)
+                               .setFragmentShader(*fragmentShader)
+                               .setPipelineLayout(this->pipelineLayout.get())
+                               .setColorAttachmentFormats({colorFormat})
+                               .setDepthAttachmentFormat(depthFormat)
+                               .setVertexInput(bindings, attributes)
+                               .setDepthTest(true, true)
+                               .setCullMode(vk::CullModeFlagBits::eBack)
+                               .build();
+}
+
+void MeshRenderSystem::createInstanceBuffers() {
+  for (std::unique_ptr<Buffer>& buffer : this->instanceBuffers) {
+    buffer = std::make_unique<Buffer>(
+        this->device, sizeof(Instance), MAX_INSTANCES_PER_FRAME,
+        vk::BufferUsageFlagBits::eVertexBuffer,
+        vk::MemoryPropertyFlagBits::eHostVisible |
+            vk::MemoryPropertyFlagBits::eHostCoherent);
+    buffer->map();
+  }
+}
+
+}  // namespace sophia

engine/src/renderer/mesh_render_system.hpp

@@ -0,0 +1,80 @@
+#pragma once
+
+#include <array>
+#include <memory>
+#include <sophia/handles.hpp>
+#include <sophia/math.hpp>
+#include <span>
+
+#include "renderer/render_context.hpp"
+#include "resources/resource_registry.hpp"
+#include "vulkan/buffer.hpp"
+#include "vulkan/device.hpp"
+#include "vulkan/pipelines/graphics_pipeline.hpp"
+
+namespace sophia {
+
+/**
+ * Draws batches of opaque meshes, depth tested and back-face culled. Knows
+ * nothing about scenes: callers hand it instances grouped into runs that
+ * share a mesh.
+ *
+ * Unlit for now: each pixel is the vertex color times the instance color.
+ * Normals and UVs reach the vertex shader but aren't used yet.
+ *
+ * Instances are written to a per-frame host-visible buffer, so every
+ * render() call within one frame appends to it; call beginFrame() once per
+ * frame before any render().
+ */
+class MeshRenderSystem {
+ public:
+  // Layout must match the per-instance inputs in mesh.vert.
+  struct Instance {
+    glm::mat4 model{1.f};
+    glm::vec4 color{1.f};
+  };
+
+  // A run of consecutive instances of the same mesh.
+  struct Batch {
+    MeshHandle mesh;
+    u32 firstInstance;
+    u32 instanceCount;
+  };
+
+  static constexpr u32 MAX_INSTANCES_PER_FRAME = 32768;
+
+  MeshRenderSystem(const MeshRenderSystem&) = delete;
+  MeshRenderSystem& operator=(const MeshRenderSystem&) = delete;
+
+  MeshRenderSystem(Device& device, vk::Format colorFormat,
+                   vk::Format depthFormat, ResourceRegistry& resources);
+  ~MeshRenderSystem();
+
+  void beginFrame(u32 frameIndex);
+
+  void render(vk::CommandBuffer commandBuffer, const glm::mat4& viewProjection,
+              std::span<const Instance> instances,
+              std::span<const Batch> batches);
+
+ private:
+  struct PushConstantData {
+    glm::mat4 viewProjection{1.f};
+  };
+
+  void createPipelineLayout();
+  void createPipeline(vk::Format colorFormat, vk::Format depthFormat);
+  void createInstanceBuffers();
+
+  Device& device;
+  ResourceRegistry& resources;
+
+  vk::UniquePipelineLayout pipelineLayout;
+  std::unique_ptr<GraphicsPipeline> graphicsPipeline;
+
+  std::array<std::unique_ptr<Buffer>, RenderContext::MAX_FRAMES_IN_FLIGHT>
+      instanceBuffers;
+  u32 frameIndex = 0;
+  u32 instanceCursor = 0;
+};
+
+}  // namespace sophia

engine/src/renderer/model_render_system.cpp

@@ -1,6 +1,7 @@
-#include "model_render_system.hpp"
+#include "renderer/model_render_system.hpp"
 
 #include <sophia/util/assert.hpp>
+#include <tracy/Tracy.hpp>
 
 #include "shaders/model_render_system.frag.spv.h"
 #include "shaders/model_render_system.vert.spv.h"
@@ -24,8 +25,8 @@ ModelRenderSystem::ModelRenderSystem(Device& device,
                             .setStage(ShaderStage::FRAGMENT)
                             .build();
 
-  auto bindingDescriptions = Mesh::Vertex::getBindingDescriptions();
+  auto bindingDescriptions = Mesh::getBindingDescriptions();
-  auto attributeDescriptions = Mesh::Vertex::getAttributeDescriptions();
+  auto attributeDescriptions = Mesh::getAttributeDescriptions();
 
   this->graphicsPipeline =
       GraphicsPipeline::Builder(device)
@@ -43,9 +44,8 @@ ModelRenderSystem::~ModelRenderSystem() {
 
 void ModelRenderSystem::render(vk::CommandBuffer commandBuffer,
                                std::span<const MeshInstance> instances,
-                               const FrameInfo& frameInfo) {
+                               const glm::mat4& viewProjection) {
-  glm::mat4 viewProjection = frameInfo.camera.getViewProjection();
+  ZoneScoped;
-
   this->graphicsPipeline->bind(commandBuffer);
 
   for (const MeshInstance& instance : instances) {

engine/src/renderer/model_render_system.hpp

@@ -1,13 +1,13 @@
 #pragma once
 
 #include <memory>
-#include <sophia/frame_info.hpp>
+#include <sophia/math.hpp>
 #include <span>
 
-#include "device.hpp"
+#include "renderer/render_context.hpp"
-#include "mesh.hpp"
+#include "resources/mesh.hpp"
-#include "pipelines/graphics_pipeline.hpp"
+#include "vulkan/device.hpp"
-#include "render_context.hpp"
+#include "vulkan/pipelines/graphics_pipeline.hpp"
 
 namespace sophia {
 
@@ -32,7 +32,7 @@ class ModelRenderSystem {
 
   void render(vk::CommandBuffer commandBuffer,
               std::span<const MeshInstance> instances,
-              const FrameInfo& frameInfo);
+              const glm::mat4& viewProjection);
 
  private:
   void createPipelineLayout();

engine/src/renderer/render_context.cpp

@@ -1,9 +1,12 @@
-#include "render_context.hpp"
+#include "renderer/render_context.hpp"
 
 #include <limits>
 #include <sophia/util/assert.hpp>
 #include <sophia/util/logger.hpp>
 #include <stdexcept>
+#include <tracy/Tracy.hpp>
+
+#include "vulkan/access.hpp"
 
 namespace sophia {
 
@@ -11,22 +14,31 @@ RenderContext::RenderContext(Window& window, Device& device)
     : window{window}, device{device} {
   createFrames();
   recreateSwapchain();
+  createTracyContext();
 }
 
-RenderContext::~RenderContext() { this->device.waitIdle(); }
+RenderContext::~RenderContext() {
+  this->device.waitIdle();
+  TracyVkDestroy(this->tracyContext);
+}
 
 vk::CommandBuffer RenderContext::beginFrame() {
+  ZoneScoped;
   SOPHIA_ASSERT(!this->isFrameStarted,
                 "Can't call beginFrame while already in progress");
 
   FrameData& frame = this->frames[this->currentFrameIndex];
 
   vk::Fence inFlightFence = frame.inFlight.get();
-  vk::Result fenceResult = this->device.get()->waitForFences(
+  vk::Result fenceResult;
-      inFlightFence, vk::True, std::numeric_limits<u64>::max());
+  {
+    ZoneScopedN("wait for frame fence");
+    fenceResult = this->device.get()->waitForFences(
+        inFlightFence, vk::True, std::numeric_limits<u64>::max());
+  }
 
   if (fenceResult != vk::Result::eSuccess) {
-    log::error("failed to wait for fence: " + vk::to_string(fenceResult));
+    log::error("failed to wait for fence: {}", vk::to_string(fenceResult));
   }
 
   vk::Semaphore imageAvailable = frame.imageAvailable.get();
@@ -50,7 +62,7 @@ vk::CommandBuffer RenderContext::beginFrame() {
         imageInFlight, vk::True, std::numeric_limits<u64>::max());
 
     if (fenceResult != vk::Result::eSuccess) {
-      log::error("failed to wait for fence: " + vk::to_string(fenceResult));
+      log::error("failed to wait for fence: {}", vk::to_string(fenceResult));
     }
   }
 
@@ -67,33 +79,42 @@ vk::CommandBuffer RenderContext::beginFrame() {
     throw std::runtime_error("failed to begin recording command buffer");
   }
 
+  TracyVkCollect(this->tracyContext,
+                 static_cast<VkCommandBuffer>(frame.commandBuffer));
+
   return frame.commandBuffer;
 }
 
 void RenderContext::endFrame() {
+  ZoneScoped;
   SOPHIA_ASSERT(this->isFrameStarted,
                 "Can't call endFrame while no frame is in progress");
 
   FrameData& frame = this->frames[this->currentFrameIndex];
   frame.commandBuffer.end();
 
-  vk::Semaphore waitSemaphore = frame.imageAvailable.get();
   vk::Semaphore signalSemaphore =
       this->renderFinishedSemaphores.at(this->currentImageIndex).get();
-  vk::PipelineStageFlags waitStage =
-      vk::PipelineStageFlagBits::eColorAttachmentOutput;
-  vk::CommandBuffer commandBuffer = frame.commandBuffer;
 
-  vk::SubmitInfo submitInfo{};
+  vk::SemaphoreSubmitInfo waitInfo{};
-  submitInfo.waitSemaphoreCount = 1;
+  waitInfo.semaphore = frame.imageAvailable.get();
-  submitInfo.pWaitSemaphores = &waitSemaphore;
+  waitInfo.stageMask = SWAPCHAIN_ACQUIRE_STAGE;
-  submitInfo.pWaitDstStageMask = &waitStage;
-  submitInfo.commandBufferCount = 1;
-  submitInfo.pCommandBuffers = &commandBuffer;
-  submitInfo.signalSemaphoreCount = 1;
-  submitInfo.pSignalSemaphores = &signalSemaphore;
 
-  this->device.getGraphicsQueue().submit(submitInfo, frame.inFlight.get());
+  // Present has no pipeline stage to wait on, so signal once everything in
+  // the submission is done.
+  vk::SemaphoreSubmitInfo signalInfo{};
+  signalInfo.semaphore = signalSemaphore;
+  signalInfo.stageMask = vk::PipelineStageFlagBits2::eAllCommands;
+
+  vk::CommandBufferSubmitInfo commandBufferInfo{};
+  commandBufferInfo.commandBuffer = frame.commandBuffer;
+
+  vk::SubmitInfo2 submitInfo{};
+  submitInfo.setWaitSemaphoreInfos(waitInfo);
+  submitInfo.setCommandBufferInfos(commandBufferInfo);
+  submitInfo.setSignalSemaphoreInfos(signalInfo);
+
+  this->device.getGraphicsQueue().submit2(submitInfo, frame.inFlight.get());
 
   vk::Result result = this->swapchain->present(
       this->device.getPresentQueue(), this->currentImageIndex, signalSemaphore);
@@ -144,6 +165,27 @@ void RenderContext::recreateSwapchain() {
   this->imagesInFlight.assign(this->swapchain->imageCount(), vk::Fence{});
 }
 
+void RenderContext::createTracyContext() {
+#ifdef TRACY_ENABLE
+  // Tracy records and submits a one-off command buffer to line up GPU and CPU
+  // clocks, and waits for it.
+  vk::CommandBufferAllocateInfo allocInfo{this->device.getCommandPool(),
+                                          vk::CommandBufferLevel::ePrimary, 1};
+  vk::CommandBuffer commandBuffer =
+      this->device.get()->allocateCommandBuffers(allocInfo).front();
+
+  this->tracyContext = TracyVkContext(
+      static_cast<VkPhysicalDevice>(this->device.getPhysicalDevice()),
+      static_cast<VkDevice>(*this->device.get()),
+      static_cast<VkQueue>(this->device.getGraphicsQueue()),
+      static_cast<VkCommandBuffer>(commandBuffer));
+  TracyVkContextName(this->tracyContext, "Graphics", 8);
+
+  this->device.get()->freeCommandBuffers(this->device.getCommandPool(),
+                                         commandBuffer);
+#endif
+}
+
 void RenderContext::createFrames() {
   vk::CommandBufferAllocateInfo allocInfo{this->device.getCommandPool(),
                                           vk::CommandBufferLevel::ePrimary,

engine/src/renderer/render_context.hpp

@@ -6,8 +6,11 @@
 #include <vector>
 #include <vulkan/vulkan.hpp>
 
-#include "device.hpp"
+/* AFTER VULKAN */
-#include "swapchain.hpp"
+#include <tracy/TracyVulkan.hpp>
+
+#include "vulkan/device.hpp"
+#include "vulkan/swapchain.hpp"
 #include "window.hpp"
 
 namespace sophia {
@@ -31,13 +34,12 @@ class RenderContext {
   vk::CommandBuffer beginFrame();
   void endFrame();
 
-  void transitionCurrentImage(vk::CommandBuffer commandBuffer,
+  Image& getCurrentImage() const {
-                              vk::ImageLayout newLayout) const {
+    return this->swapchain->getImage(static_cast<int>(this->currentImageIndex));
-    this->swapchain->getImage(static_cast<int>(this->currentImageIndex))
-        .transitionLayout(commandBuffer, newLayout);
   }
-  vk::ImageView getCurrentImageView() const {
+
-    return this->swapchain->getImageView(
+  Image& getCurrentDepthImage() const {
+    return this->swapchain->getDepthImage(
         static_cast<int>(this->currentImageIndex));
   }
 
@@ -45,6 +47,8 @@ class RenderContext {
   vk::Format getImageFormat() const {
     return this->swapchain->getImageFormat();
   }
+  u32 getFrameIndex() const { return this->currentFrameIndex; }
+  TracyVkCtx getTracyContext() const { return this->tracyContext; }
   u32 getImageCount() const {
     return static_cast<u32>(this->swapchain->imageCount());
   }
@@ -52,6 +56,7 @@ class RenderContext {
  private:
   void recreateSwapchain();
   void createFrames();
+  void createTracyContext();
 
   Window& window;
   Device& device;
@@ -63,6 +68,8 @@ class RenderContext {
   std::vector<vk::UniqueSemaphore> renderFinishedSemaphores;
   std::vector<vk::Fence> imagesInFlight;
 
+  TracyVkCtx tracyContext = nullptr;
+
   u32 currentFrameIndex = 0;
   u32 currentImageIndex = 0;
   bool isFrameStarted = false;

engine/src/renderer/render_graph.cpp

@@ -0,0 +1,195 @@
+#include "renderer/render_graph.hpp"
+
+#include <sophia/util/assert.hpp>
+#include <tracy/Tracy.hpp>
+#include <utility>
+
+#include "vulkan/debug_label.hpp"
+
+namespace sophia {
+
+ImageRef RenderGraph::importImage(Image& image, Access finalAccess) {
+  ImageRef ref{static_cast<u32>(this->images.size())};
+  this->images.push_back({&image, finalAccess, image.getAccessState()});
+  return ref;
+}
+
+void RenderGraph::addPass(std::string name, const SetupFn& setup,
+                          ExecuteFn execute) {
+  Pass& pass = this->passes.emplace_back();
+  pass.name = std::move(name);
+  pass.execute = std::move(execute);
+
+  PassBuilder builder{*this, pass};
+  setup(builder);
+}
+
+void RenderGraph::execute(vk::CommandBuffer commandBuffer) {
+  ZoneScoped;
+  for (Pass& pass : this->passes) {
+    this->recordPass(commandBuffer, pass);
+  }
+
+  PendingBarriers pending;
+  for (u32 i = 0; i < this->images.size(); i++) {
+    this->transitionTo(ImageRef{i}, getAccessState(this->images[i].finalAccess),
+                       pending);
+  }
+  this->flush(commandBuffer, pending);
+
+  for (ImportedImage& imported : this->images) {
+    imported.image->recordLayout(imported.state.layout);
+  }
+
+  this->passes.clear();
+}
+
+void RenderGraph::transitionTo(ImageRef ref, const AccessState& next,
+                               PendingBarriers& pending) {
+  SOPHIA_ASSERT(ref.isValid() && ref.index < this->images.size(),
+                "ImageRef doesn't belong to this graph");
+
+  ImportedImage& imported = this->images[ref.index];
+
+  if (needsBarrier(imported.state, next)) {
+    pending.barriers.push_back(makeImageBarrier(
+        imported.image->get(), imported.image->getSubresourceRange(),
+        imported.state, next));
+    imported.state = next;
+  } else {
+    // Same-layout read after read. Nothing to record, but a later write has
+    // to wait on this reader too.
+    imported.state.stage |= next.stage;
+    imported.state.access |= next.access;
+  }
+}
+
+void RenderGraph::flush(vk::CommandBuffer commandBuffer,
+                        PendingBarriers& pending) {
+  recordImageBarriers(commandBuffer, pending.barriers);
+  pending = PendingBarriers{};
+}
+
+void RenderGraph::recordPass(vk::CommandBuffer commandBuffer, Pass& pass) {
+  ZoneTransientN(cpuZone, pass.name.c_str(), true);
+  TracyVkZoneTransient(this->tracyContext, gpuZone,
+                       static_cast<VkCommandBuffer>(commandBuffer),
+                       pass.name.c_str(), this->tracyContext != nullptr);
+  beginDebugLabel(commandBuffer, pass.name.c_str());
+
+  PendingBarriers pending;
+  for (const ImageUse& use : pass.uses) {
+    this->transitionTo(use.image, getAccessState(use.access), pending);
+  }
+  this->flush(commandBuffer, pending);
+
+  if (pass.colorAttachments.empty() && !pass.depthAttachment) {
+    pass.execute(commandBuffer);
+  } else {
+    this->recordRendering(commandBuffer, pass);
+  }
+
+  endDebugLabel(commandBuffer);
+}
+
+void RenderGraph::recordRendering(vk::CommandBuffer commandBuffer, Pass& pass) {
+  std::vector<vk::RenderingAttachmentInfo> attachments;
+  attachments.reserve(pass.colorAttachments.size());
+
+  ImageRef sizedBy = pass.colorAttachments.empty()
+                         ? pass.depthAttachment->image
+                         : pass.colorAttachments.front().image;
+  vk::Extent3D imageExtent = this->images[sizedBy.index].image->getExtent();
+  vk::Extent2D extent{imageExtent.width, imageExtent.height};
+
+  for (const ColorAttachment& color : pass.colorAttachments) {
+    const Image& image = *this->images[color.image.index].image;
+    SOPHIA_ASSERT(image.getExtent().width == extent.width &&
+                      image.getExtent().height == extent.height,
+                  "Pass {} has color attachments of different sizes",
+                  pass.name);
+
+    vk::RenderingAttachmentInfo attachment{};
+    attachment.imageView = image.getView();
+    attachment.imageLayout = vk::ImageLayout::eColorAttachmentOptimal;
+    attachment.loadOp = color.loadOp;
+    attachment.storeOp = vk::AttachmentStoreOp::eStore;
+    attachment.clearValue.color = vk::ClearColorValue{color.clearColor};
+    attachments.push_back(attachment);
+  }
+
+  vk::RenderingInfo renderingInfo{};
+  renderingInfo.renderArea = vk::Rect2D{{0, 0}, extent};
+  renderingInfo.layerCount = 1;
+  renderingInfo.colorAttachmentCount = static_cast<u32>(attachments.size());
+  renderingInfo.pColorAttachments = attachments.data();
+
+  vk::RenderingAttachmentInfo depthAttachment{};
+  if (pass.depthAttachment) {
+    const Image& image = *this->images[pass.depthAttachment->image.index].image;
+    SOPHIA_ASSERT(image.getExtent().width == extent.width &&
+                      image.getExtent().height == extent.height,
+                  "Pass {} has a depth attachment of a different size",
+                  pass.name);
+
+    depthAttachment.imageView = image.getView();
+    depthAttachment.imageLayout =
+        vk::ImageLayout::eDepthStencilAttachmentOptimal;
+    depthAttachment.loadOp = pass.depthAttachment->loadOp;
+    depthAttachment.storeOp = vk::AttachmentStoreOp::eStore;
+    depthAttachment.clearValue.depthStencil =
+        vk::ClearDepthStencilValue{pass.depthAttachment->clearDepth, 0};
+    renderingInfo.pDepthAttachment = &depthAttachment;
+  }
+
+  commandBuffer.beginRendering(renderingInfo);
+
+  vk::Viewport viewport{0.0f,
+                        0.0f,
+                        static_cast<float>(extent.width),
+                        static_cast<float>(extent.height),
+                        0.0f,
+                        1.0f};
+  vk::Rect2D scissor{{0, 0}, extent};
+  commandBuffer.setViewport(0, viewport);
+  commandBuffer.setScissor(0, scissor);
+
+  pass.execute(commandBuffer);
+
+  commandBuffer.endRendering();
+}
+
+RenderGraph::PassBuilder& RenderGraph::PassBuilder::writeColor(
+    ImageRef image, vk::AttachmentLoadOp loadOp, ClearColor clearColor) {
+  this->use(image, Access::ColorWrite);
+  this->pass.colorAttachments.push_back({image, loadOp, clearColor});
+  return *this;
+}
+
+RenderGraph::PassBuilder& RenderGraph::PassBuilder::writeDepth(
+    ImageRef image, vk::AttachmentLoadOp loadOp, float clearDepth) {
+  SOPHIA_ASSERT(!this->pass.depthAttachment,
+                "Pass {} already has a depth attachment", this->pass.name);
+  this->use(image, Access::DepthWrite);
+  this->pass.depthAttachment = DepthAttachment{image, loadOp, clearDepth};
+  return *this;
+}
+
+RenderGraph::PassBuilder& RenderGraph::PassBuilder::sample(ImageRef image) {
+  return this->use(image, Access::SampledRead);
+}
+
+RenderGraph::PassBuilder& RenderGraph::PassBuilder::use(ImageRef image,
+                                                        Access access) {
+  SOPHIA_ASSERT(image.isValid() && image.index < this->graph.images.size(),
+                "ImageRef doesn't belong to this graph");
+  for (const ImageUse& existing : this->pass.uses) {
+    SOPHIA_ASSERT(existing.image.index != image.index,
+                  "Pass {} uses the same image twice", this->pass.name);
+  }
+
+  this->pass.uses.push_back({image, access});
+  return *this;
+}
+
+}  // namespace sophia

engine/src/renderer/render_graph.hpp

@@ -0,0 +1,168 @@
+#pragma once
+
+#include <array>
+#include <functional>
+#include <optional>
+#include <sophia/types.hpp>
+#include <string>
+#include <vector>
+#include <vulkan/vulkan.hpp>
+// After Vulkan, which it expects to already be declared.
+#include <tracy/TracyVulkan.hpp>
+
+#include "vulkan/access.hpp"
+#include "vulkan/image.hpp"
+
+namespace sophia {
+
+/**
+ * Names an image within one RenderGraph. Only valid for the graph that
+ * returned it.
+ */
+struct ImageRef {
+  u32 index = INVALID_INDEX;
+
+  static constexpr u32 INVALID_INDEX = 0xFFFFFFFF;
+
+  bool isValid() const { return this->index != INVALID_INDEX; }
+};
+
+using ClearColor = std::array<float, 4>;
+
+/**
+ * A frame's passes and the images they touch, recorded into a single command
+ * buffer. Passes run in the order they were added; the graph's job is to
+ * work out the barriers and layout transitions between them from what each
+ * pass says it does to each image, and to begin/end rendering for passes that
+ * write color or depth attachments.
+ *
+ * Built fresh every frame:
+ *
+ *   RenderGraph graph;
+ *   ImageRef backbuffer = graph.importImage(swapchainImage, Access::Present);
+ *   graph.addPass(
+ *       "main", [&](PassBuilder& pass) { pass.writeColor(backbuffer); },
+ *       [&](vk::CommandBuffer cb) { draw(cb); });
+ *   graph.execute(commandBuffer);
+ *
+ * Imported images start in whatever layout Image reports and are left in
+ * their final access when execute() returns, with the Image's tracked layout
+ * updated to match.
+ */
+class RenderGraph {
+ public:
+  class PassBuilder;
+
+  using SetupFn = std::function<void(PassBuilder&)>;
+  using ExecuteFn = std::function<void(vk::CommandBuffer)>;
+
+  explicit RenderGraph(TracyVkCtx tracyContext = nullptr)
+      : tracyContext{tracyContext} {}
+
+  RenderGraph(const RenderGraph&) = delete;
+  RenderGraph& operator=(const RenderGraph&) = delete;
+
+  /**
+   * Brings an image the graph doesn't own into it. It must outlive
+   * execute(). After the last pass it is transitioned to `finalAccess`.
+   */
+  ImageRef importImage(Image& image, Access finalAccess);
+
+  /**
+   * Adds a pass. `setup` runs immediately and declares what the pass does to
+   * images; `execute` runs later, from execute(), with the barriers already
+   * recorded and (if the pass writes color or depth) rendering begun. `name`
+   * labels the pass's commands in debugging tools such as RenderDoc.
+   */
+  void addPass(std::string name, const SetupFn& setup, ExecuteFn execute);
+
+  /**
+   * Records every pass, and the barriers between them, into `commandBuffer`.
+   */
+  void execute(vk::CommandBuffer commandBuffer);
+
+ private:
+  struct ImageUse {
+    ImageRef image;
+    Access access;
+  };
+
+  struct ColorAttachment {
+    ImageRef image;
+    vk::AttachmentLoadOp loadOp;
+    ClearColor clearColor;
+  };
+
+  struct DepthAttachment {
+    ImageRef image;
+    vk::AttachmentLoadOp loadOp;
+    float clearDepth;
+  };
+
+  struct Pass {
+    std::string name;
+    std::vector<ImageUse> uses;
+    std::vector<ColorAttachment> colorAttachments;
+    std::optional<DepthAttachment> depthAttachment;
+    ExecuteFn execute;
+  };
+
+  struct ImportedImage {
+    Image* image;
+    Access finalAccess;
+    // What the image was last left in, as of the barriers recorded so far.
+    AccessState state;
+  };
+
+  struct PendingBarriers {
+    std::vector<vk::ImageMemoryBarrier2> barriers;
+  };
+
+  void transitionTo(ImageRef ref, const AccessState& next,
+                    PendingBarriers& pending);
+  void flush(vk::CommandBuffer commandBuffer, PendingBarriers& pending);
+  void recordPass(vk::CommandBuffer commandBuffer, Pass& pass);
+  void recordRendering(vk::CommandBuffer commandBuffer, Pass& pass);
+
+  TracyVkCtx tracyContext;
+  std::vector<ImportedImage> images;
+  std::vector<Pass> passes;
+};
+
+class RenderGraph::PassBuilder {
+ public:
+  /**
+   * Renders into `image` as a color attachment. Passes with one or more of
+   * these get rendering begun (and viewport/scissor set to the attachment's
+   * extent) before their execute callback runs.
+   */
+  PassBuilder& writeColor(
+      ImageRef image,
+      vk::AttachmentLoadOp loadOp = vk::AttachmentLoadOp::eClear,
+      ClearColor clearColor = {0.f, 0.f, 0.f, 1.f});
+
+  /**
+   * Renders with `image` as the depth attachment, which must be the same size
+   * as any color attachments. At most one per pass.
+   */
+  PassBuilder& writeDepth(
+      ImageRef image,
+      vk::AttachmentLoadOp loadOp = vk::AttachmentLoadOp::eClear,
+      float clearDepth = 1.f);
+
+  /** Samples `image` in a shader. */
+  PassBuilder& sample(ImageRef image);
+
+  /** Any other use, e.g. storage or transfer access. */
+  PassBuilder& use(ImageRef image, Access access);
+
+ private:
+  friend class RenderGraph;
+
+  PassBuilder(RenderGraph& graph, Pass& pass) : graph{graph}, pass{pass} {}
+
+  RenderGraph& graph;
+  Pass& pass;
+};
+
+}  // namespace sophia

engine/src/renderer/renderer.cpp

@@ -0,0 +1,9 @@
+#include "renderer/renderer.hpp"
+
+namespace sophia {
+
+Renderer::Renderer() {}
+
+Renderer::~Renderer() {}
+
+}  // namespace sophia

engine/src/renderer/renderer.hpp

@@ -0,0 +1,91 @@
+#pragma once
+
+#include <sophia/handles.hpp>
+#include <sophia/math.hpp>
+#include <sophia/types.hpp>
+#include <string>
+#include <vector>
+
+#include "vulkan/buffer.hpp"
+
+namespace sophia {
+
+struct DrawPacket {
+  /* Geometry */
+  // BufferHandle vertexBuffer;
+  // BufferHandle indexBuffer;
+  u32 indexCount;
+  u32 firstIndex;
+
+  /* Shader & state */
+  // PipelineHandle pipelineState; // Contains shaders, blend state, depth
+  // settings
+
+  /* Bindings */
+  // DescriptorSetHandle resourceBindings;  // Textures, Uniform Buffers,
+  // Storage Buffers
+
+  /* Transform / Constants */
+  u32 pushConstantData[16];
+};
+
+struct RenderView {
+  mat4 view;
+  mat4 projection;
+  vec2 viewport;
+
+  RenderTargetHandle target;
+};
+
+// struct ComputePacket {
+//   ComputePipelineHandle pipeline;
+//   DescriptorSetHandle
+//       resourceBindings;  // Includes storage buffers, uniforms, textures
+
+//   // Grid dimensions
+//   uint32_t groupCountX = 1;
+//   uint32_t groupCountY = 1;
+//   uint32_t groupCountZ = 1;
+
+//   // Optional push constants for dynamic per-dispatch parameters
+//   uint8_t pushConstants[64];
+//   uint32_t pushConstantSize = 0;
+// };
+
+// !TODO move to render graph
+enum class RenderPassType { Graphics, Compute };
+
+// !TODO move to render graph (???)
+struct RenderPass {
+  std::string name;
+  RenderPassType type;
+
+  // Declared for automatic barrier injection & resource synchronization
+  std::vector<Buffer> readBuffers;   // BufferHandle instead?
+  std::vector<Buffer> writeBuffers;  // BufferHandle instead?
+
+  // Commands in this pass
+  // std::vector<ComputePacket> computeDispatches;
+  std::vector<DrawPacket> opaqueDrawPackets;
+  std::vector<DrawPacket> transparentDrawPackets;
+};
+
+struct RenderPacket {
+  RenderView view;
+  std::vector<RenderPass> passes;
+};
+
+class Renderer {
+ public:
+  Renderer(const Renderer&) = delete;
+  Renderer& operator=(const Renderer&) = delete;
+
+  Renderer();
+  ~Renderer();
+
+  // PipelineHandle createPipeline();
+
+ private:
+};
+
+}  // namespace sophia

engine/src/renderer/scene_renderer.cpp

@@ -0,0 +1,163 @@
+#include "renderer/scene_renderer.hpp"
+
+#include <algorithm>
+#include <sophia/components.hpp>
+#include <sophia/util/assert.hpp>
+#include <tracy/Tracy.hpp>
+#include <tuple>
+
+namespace sophia {
+
+SceneRenderer::SceneRenderer(const SceneRegistry& sceneRegistry,
+                             ResourceRegistry& resources, Device& device,
+                             vk::Format colorFormat)
+    : sceneRegistry{sceneRegistry},
+      resources{resources},
+      meshRenderSystem{device, colorFormat,
+                       resources.renderTargetPool.getDepthFormat(), resources},
+      spriteRenderSystem{device, colorFormat,
+                         resources.renderTargetPool.getDepthFormat(),
+                         resources} {}
+
+void SceneRenderer::beginFrame(u32 frameIndex) {
+  ZoneScoped;
+  this->meshRenderSystem.beginFrame(frameIndex);
+  this->spriteRenderSystem.beginFrame(frameIndex);
+}
+
+void SceneRenderer::render(vk::CommandBuffer commandBuffer,
+                           const SceneView& sceneView, Entity camera,
+                           vk::Extent2D extent) {
+  ZoneScoped;
+  SOPHIA_ASSERT(camera.hasComponent<CameraComponent>(),
+                "camera does not have camera component!");
+
+  float aspect =
+      static_cast<float>(extent.width) / static_cast<float>(extent.height);
+
+  glm::mat4 view =
+      CameraComponent::getView(camera.getComponent<TransformComponent>());
+  glm::mat4 projection =
+      camera.getComponent<CameraComponent>().getProjection(aspect);
+
+  const Scene& scene = this->sceneRegistry.get(sceneView.scene);
+  glm::mat4 viewProjection = projection * view;
+
+  // Opaque first, so sprites blend over the meshes behind them.
+  renderMeshes(commandBuffer, scene, viewProjection);
+  renderSprites(commandBuffer, scene, view, viewProjection);
+}
+
+void SceneRenderer::renderMeshes(vk::CommandBuffer commandBuffer,
+                                 const Scene& scene,
+                                 const glm::mat4& viewProjection) {
+  ZoneScoped;
+  this->meshDrawItems.clear();
+
+  {
+    ZoneScopedN("meshes: gather");
+    auto meshes =
+        scene.registry.view<const TransformComponent, const MeshComponent>();
+    for (auto [entity, transform, mesh] : meshes.each()) {
+      if (!this->resources.meshPool.isAlive(mesh.handle)) {
+        continue;
+      }
+      this->meshDrawItems.push_back(
+          {mesh.handle, {transform.mat4(), mesh.color}});
+    }
+  }
+
+  {
+    ZoneScopedN("meshes: sort");
+    // Opaque, so order only matters for batching: one batch per mesh.
+    std::ranges::sort(this->meshDrawItems, {},
+                      [](const MeshDrawItem& item) { return item.mesh; });
+  }
+
+  {
+    ZoneScopedN("meshes: batch");
+    this->meshInstances.clear();
+    this->meshBatches.clear();
+    for (const MeshDrawItem& item : this->meshDrawItems) {
+      auto index = static_cast<u32>(this->meshInstances.size());
+      this->meshInstances.push_back(item.instance);
+
+      if (this->meshBatches.empty() ||
+          this->meshBatches.back().mesh != item.mesh) {
+        this->meshBatches.push_back({item.mesh, index, 0});
+      }
+      this->meshBatches.back().instanceCount++;
+    }
+  }
+
+  TracyPlot("mesh instances", static_cast<int64_t>(this->meshInstances.size()));
+  TracyPlot("mesh batches", static_cast<int64_t>(this->meshBatches.size()));
+
+  this->meshRenderSystem.render(commandBuffer, viewProjection,
+                                this->meshInstances, this->meshBatches);
+}
+
+void SceneRenderer::renderSprites(vk::CommandBuffer commandBuffer,
+                                  const Scene& scene, const glm::mat4& view,
+                                  const glm::mat4& viewProjection) {
+  ZoneScoped;
+  this->spriteDrawItems.clear();
+
+  {
+    ZoneScopedN("sprites: gather");
+    auto sprites =
+        scene.registry.view<const TransformComponent, const SpriteComponent>();
+    for (auto [entity, transform, sprite] : sprites.each()) {
+      TextureHandle texture =
+          this->resources.texturePool.isAlive(sprite.texture)
+              ? sprite.texture
+              : this->resources.whiteTexture;
+
+      // Distance in front of the camera, which looks down view-space -Z.
+      float depth = -(view * glm::vec4{transform.position, 1.f}).z;
+
+      this->spriteDrawItems.push_back(
+          {sprite.sortOrder,
+           depth,
+           texture,
+           {sprite.getModel(transform), sprite.color, sprite.uvRect}});
+    }
+  }
+
+  {
+    ZoneScopedN("sprites: sort");
+    // Within a sortOrder, back to front, so nearer sprites blend over farther
+    // ones. Texture is the last key so that sprites whose order doesn't
+    // matter relative to each other still end up in as few batches as
+    // possible.
+    std::ranges::sort(
+        this->spriteDrawItems, {}, [](const SpriteDrawItem& item) {
+          return std::tuple{item.sortOrder, -item.depth, item.texture};
+        });
+  }
+
+  {
+    ZoneScopedN("sprites: batch");
+    this->spriteInstances.clear();
+    this->spriteBatches.clear();
+    for (const SpriteDrawItem& item : this->spriteDrawItems) {
+      auto index = static_cast<u32>(this->spriteInstances.size());
+      this->spriteInstances.push_back(item.instance);
+
+      if (this->spriteBatches.empty() ||
+          this->spriteBatches.back().texture != item.texture) {
+        this->spriteBatches.push_back({item.texture, index, 0});
+      }
+      this->spriteBatches.back().instanceCount++;
+    }
+  }
+
+  TracyPlot("sprite instances",
+            static_cast<int64_t>(this->spriteInstances.size()));
+  TracyPlot("sprite batches", static_cast<int64_t>(this->spriteBatches.size()));
+
+  this->spriteRenderSystem.render(commandBuffer, viewProjection,
+                                  this->spriteInstances, this->spriteBatches);
+}
+
+}  // namespace sophia

engine/src/renderer/scene_renderer.hpp

@@ -0,0 +1,69 @@
+#pragma once
+
+#include <sophia/scene_registry.hpp>
+#include <sophia/scene_view.hpp>
+#include <vector>
+
+#include "renderer/mesh_render_system.hpp"
+#include "renderer/sprite_render_system.hpp"
+#include "resources/resource_registry.hpp"
+
+namespace sophia {
+
+/**
+ * !TEMP to be decoupled once scene batching and rendering impl
+ *
+ * Turns a scene's components into draw calls for a SceneView.
+ */
+class SceneRenderer {
+ public:
+  SceneRenderer(const SceneRenderer&) = delete;
+  SceneRenderer& operator=(const SceneRenderer&) = delete;
+
+  SceneRenderer(const SceneRegistry& sceneRegistry, ResourceRegistry& resources,
+                Device& device, vk::Format colorFormat);
+
+  // Call once per frame, before any render().
+  void beginFrame(u32 frameIndex);
+
+  // Records `sceneView` as seen through `camera` (an entity of the view's
+  // scene with a CameraComponent) into `commandBuffer`. Rendering into the
+  // view's target, which is `extent` in size, must already have begun.
+  void render(vk::CommandBuffer commandBuffer, const SceneView& sceneView,
+              Entity camera, vk::Extent2D extent);
+
+ private:
+  struct MeshDrawItem {
+    MeshHandle mesh;
+    MeshRenderSystem::Instance instance;
+  };
+
+  struct SpriteDrawItem {
+    s32 sortOrder;
+    // Distance in front of the camera.
+    float depth;
+    TextureHandle texture;
+    SpriteRenderSystem::Instance instance;
+  };
+
+  void renderMeshes(vk::CommandBuffer commandBuffer, const Scene& scene,
+                    const glm::mat4& viewProjection);
+  void renderSprites(vk::CommandBuffer commandBuffer, const Scene& scene,
+                     const glm::mat4& view, const glm::mat4& viewProjection);
+
+  const SceneRegistry& sceneRegistry;
+  ResourceRegistry& resources;
+
+  MeshRenderSystem meshRenderSystem;
+  SpriteRenderSystem spriteRenderSystem;
+
+  // Reused across frames to avoid reallocating.
+  std::vector<MeshDrawItem> meshDrawItems;
+  std::vector<MeshRenderSystem::Instance> meshInstances;
+  std::vector<MeshRenderSystem::Batch> meshBatches;
+  std::vector<SpriteDrawItem> spriteDrawItems;
+  std::vector<SpriteRenderSystem::Instance> spriteInstances;
+  std::vector<SpriteRenderSystem::Batch> spriteBatches;
+};
+
+}  // namespace sophia

engine/src/renderer/sprite_render_system.cpp

@@ -0,0 +1,202 @@
+#include "renderer/sprite_render_system.hpp"
+
+#include <sophia/util/assert.hpp>
+#include <sophia/util/logger.hpp>
+#include <tracy/Tracy.hpp>
+
+#include "shaders/sprite.frag.spv.h"
+#include "shaders/sprite.vert.spv.h"
+#include "vulkan/descriptors/descriptor_writer.hpp"
+
+namespace sophia {
+
+namespace {
+constexpr u32 MAX_TEXTURES = 1024;
+constexpr u32 VERTICES_PER_SPRITE = 6;
+}  // namespace
+
+SpriteRenderSystem::SpriteRenderSystem(Device& device, vk::Format colorFormat,
+                                       vk::Format depthFormat,
+                                       ResourceRegistry& resources)
+    : device{device}, resources{resources} {
+  createDescriptors();
+  createPipelineLayout();
+  createPipeline(colorFormat, depthFormat);
+  createInstanceBuffers();
+}
+
+SpriteRenderSystem::~SpriteRenderSystem() {
+  log::trace("destroyed sophia::SpriteRenderSystem");
+}
+
+void SpriteRenderSystem::beginFrame(u32 frameIndex) {
+  this->frameIndex = frameIndex;
+  this->instanceCursor = 0;
+}
+
+void SpriteRenderSystem::render(vk::CommandBuffer commandBuffer,
+                                const glm::mat4& viewProjection,
+                                std::span<const Instance> instances,
+                                std::span<const Batch> batches) {
+  ZoneScoped;
+  if (instances.empty()) {
+    return;
+  }
+
+  u32 available = MAX_INSTANCES_PER_FRAME - this->instanceCursor;
+  if (instances.size() > available) {
+    log::warning(
+        "SpriteRenderSystem: frame instance buffer full, dropping {} sprites",
+        instances.size() - available);
+  }
+
+  Buffer& buffer = *this->instanceBuffers[this->frameIndex];
+  u32 base = this->instanceCursor;
+  u32 count = std::min(static_cast<u32>(instances.size()), available);
+  buffer.writeToBuffer(const_cast<Instance*>(instances.data()),
+                       count * sizeof(Instance), base * sizeof(Instance));
+  this->instanceCursor += count;
+
+  this->graphicsPipeline->bind(commandBuffer);
+
+  PushConstantData push{viewProjection};
+  commandBuffer.pushConstants(this->pipelineLayout.get(),
+                              vk::ShaderStageFlagBits::eVertex, 0,
+                              sizeof(PushConstantData), &push);
+
+  vk::Buffer vertexBuffer = buffer.getBuffer();
+  vk::DeviceSize offset = 0;
+  commandBuffer.bindVertexBuffers(0, 1, &vertexBuffer, &offset);
+
+  for (const Batch& batch : batches) {
+    if (batch.firstInstance >= count) {
+      break;
+    }
+    u32 batchCount = std::min(batch.instanceCount, count - batch.firstInstance);
+
+    vk::DescriptorSet set = getDescriptorSet(batch.texture);
+    commandBuffer.bindDescriptorSets(vk::PipelineBindPoint::eGraphics,
+                                     this->pipelineLayout.get(), 0, 1, &set, 0,
+                                     nullptr);
+    commandBuffer.draw(VERTICES_PER_SPRITE, batchCount, 0,
+                       base + batch.firstInstance);
+  }
+}
+
+vk::DescriptorSet SpriteRenderSystem::getDescriptorSet(TextureHandle handle) {
+  auto it = this->descriptorSets.find(handle.index);
+  if (it != this->descriptorSets.end() &&
+      it->second.generation == handle.generation) {
+    return it->second.set;
+  }
+
+  const Texture& texture = this->resources.texturePool.get(handle);
+  vk::DescriptorImageInfo imageInfo = texture.descriptorInfo();
+  DescriptorWriter writer{*this->setLayout, *this->descriptorPool};
+  writer.writeImage(0, &imageInfo);
+
+  if (it == this->descriptorSets.end()) {
+    vk::DescriptorSet set;
+    bool allocated = writer.build(set);
+    SOPHIA_ASSERT(allocated, "SpriteRenderSystem: out of texture descriptors");
+    this->descriptorSets.emplace(static_cast<u32>(handle.index),
+                                 CachedDescriptorSet{handle.generation, set});
+    return set;
+  }
+
+  // The slot was reused by a new texture. Releasing a texture waits for the
+  // device to go idle, so no in-flight frame can still be using this set.
+  writer.overwrite(it->second.set);
+  it->second.generation = handle.generation;
+  return it->second.set;
+}
+
+void SpriteRenderSystem::createDescriptors() {
+  this->setLayout =
+      DescriptorSetLayout::Builder(this->device)
+          .addBinding(0, vk::DescriptorType::eCombinedImageSampler,
+                      vk::ShaderStageFlagBits::eFragment)
+          .build();
+
+  this->descriptorPool =
+      DescriptorPool::Builder(this->device)
+          .setMaxSets(MAX_TEXTURES)
+          .addPoolSize(vk::DescriptorType::eCombinedImageSampler, MAX_TEXTURES)
+          .build();
+}
+
+void SpriteRenderSystem::createPipelineLayout() {
+  vk::PushConstantRange pushConstantRange{};
+  pushConstantRange.stageFlags = vk::ShaderStageFlagBits::eVertex;
+  pushConstantRange.offset = 0;
+  pushConstantRange.size = sizeof(PushConstantData);
+
+  vk::DescriptorSetLayout setLayout = this->setLayout->getDescriptorSetLayout();
+
+  vk::PipelineLayoutCreateInfo pipelineLayoutInfo = {};
+  pipelineLayoutInfo.setLayoutCount = 1;
+  pipelineLayoutInfo.pSetLayouts = &setLayout;
+  pipelineLayoutInfo.pushConstantRangeCount = 1;
+  pipelineLayoutInfo.pPushConstantRanges = &pushConstantRange;
+
+  try {
+    this->pipelineLayout =
+        this->device.get()->createPipelineLayoutUnique(pipelineLayoutInfo);
+    log::trace("created vk::PipelineLayout");
+  } catch (const vk::SystemError& err) {
+    log::fatal("failed to create vk::PipelineLayout");
+    throw std::runtime_error("failed to create vk::PipelineLayout");
+  }
+}
+
+void SpriteRenderSystem::createPipeline(vk::Format colorFormat,
+                                        vk::Format depthFormat) {
+  auto vertexShader = Shader::Builder()
+                          .fromSPIRV(shaders::sprite_vert_spv)
+                          .setStage(ShaderStage::VERTEX)
+                          .build();
+  auto fragmentShader = Shader::Builder()
+                            .fromSPIRV(shaders::sprite_frag_spv)
+                            .setStage(ShaderStage::FRAGMENT)
+                            .build();
+
+  std::vector<vk::VertexInputBindingDescription> bindings{
+      {0, sizeof(Instance), vk::VertexInputRate::eInstance}};
+
+  std::vector<vk::VertexInputAttributeDescription> attributes;
+  // A mat4 attribute takes four consecutive locations, one per column.
+  for (u32 column = 0; column < 4; column++) {
+    attributes.push_back({column, 0, vk::Format::eR32G32B32A32Sfloat,
+                          static_cast<u32>(offsetof(Instance, model) +
+                                           column * sizeof(glm::vec4))});
+  }
+  attributes.push_back({4, 0, vk::Format::eR32G32B32A32Sfloat,
+                        static_cast<u32>(offsetof(Instance, color))});
+  attributes.push_back({5, 0, vk::Format::eR32G32B32A32Sfloat,
+                        static_cast<u32>(offsetof(Instance, uvRect))});
+
+  this->graphicsPipeline =
+      GraphicsPipeline::Builder(this->device)
+          .setVertexShader(*vertexShader)
+          .setFragmentShader(*fragmentShader)
+          .setPipelineLayout(this->pipelineLayout.get())
+          .setColorAttachmentFormats({colorFormat})
+          .setDepthAttachmentFormat(depthFormat)
+          .setVertexInput(bindings, attributes)
+          .setAlphaBlending()
+          .setDepthTest(true, false, vk::CompareOp::eLessOrEqual)
+          .build();
+}
+
+void SpriteRenderSystem::createInstanceBuffers() {
+  for (std::unique_ptr<Buffer>& buffer : this->instanceBuffers) {
+    buffer = std::make_unique<Buffer>(
+        this->device, sizeof(Instance), MAX_INSTANCES_PER_FRAME,
+        vk::BufferUsageFlagBits::eVertexBuffer,
+        vk::MemoryPropertyFlagBits::eHostVisible |
+            vk::MemoryPropertyFlagBits::eHostCoherent);
+    buffer->map();
+  }
+}
+
+}  // namespace sophia

engine/src/renderer/sprite_render_system.hpp

@@ -0,0 +1,96 @@
+#pragma once
+
+#include <array>
+#include <memory>
+#include <sophia/handles.hpp>
+#include <sophia/math.hpp>
+#include <span>
+#include <unordered_map>
+
+#include "renderer/render_context.hpp"
+#include "resources/resource_registry.hpp"
+#include "vulkan/buffer.hpp"
+#include "vulkan/descriptors/descriptor_pool.hpp"
+#include "vulkan/descriptors/descriptor_set_layout.hpp"
+#include "vulkan/device.hpp"
+#include "vulkan/pipelines/graphics_pipeline.hpp"
+
+namespace sophia {
+
+/**
+ * Draws batches of textured quads. Knows nothing about scenes: callers hand
+ * it instances already in draw order, grouped into runs that share a texture.
+ * Sprites are depth tested, so opaque geometry in front hides them, but
+ * don't write depth, since they blend.
+ *
+ * Instances are written to a per-frame host-visible buffer, so every
+ * render() call within one frame appends to it; call beginFrame() once per
+ * frame before any render().
+ */
+class SpriteRenderSystem {
+ public:
+  // Layout must match the per-instance inputs in sprite.vert.
+  struct Instance {
+    glm::mat4 model{1.f};
+    glm::vec4 color{1.f};
+    glm::vec4 uvRect{0.f, 0.f, 1.f, 1.f};
+  };
+
+  // A run of consecutive instances drawn with the same texture.
+  struct Batch {
+    TextureHandle texture;
+    u32 firstInstance;
+    u32 instanceCount;
+  };
+
+  static constexpr u32 MAX_INSTANCES_PER_FRAME = 32768;
+
+  SpriteRenderSystem(const SpriteRenderSystem&) = delete;
+  SpriteRenderSystem& operator=(const SpriteRenderSystem&) = delete;
+
+  SpriteRenderSystem(Device& device, vk::Format colorFormat,
+                     vk::Format depthFormat, ResourceRegistry& resources);
+  ~SpriteRenderSystem();
+
+  void beginFrame(u32 frameIndex);
+
+  void render(vk::CommandBuffer commandBuffer, const glm::mat4& viewProjection,
+              std::span<const Instance> instances,
+              std::span<const Batch> batches);
+
+ private:
+  struct PushConstantData {
+    glm::mat4 viewProjection{1.f};
+  };
+
+  struct CachedDescriptorSet {
+    u32 generation;
+    vk::DescriptorSet set;
+  };
+
+  void createDescriptors();
+  void createPipelineLayout();
+  void createPipeline(vk::Format colorFormat, vk::Format depthFormat);
+  void createInstanceBuffers();
+
+  vk::DescriptorSet getDescriptorSet(TextureHandle handle);
+
+  Device& device;
+  ResourceRegistry& resources;
+
+  std::unique_ptr<DescriptorSetLayout> setLayout;
+  std::unique_ptr<DescriptorPool> descriptorPool;
+  // One set per texture slot, keyed by handle index. A generation mismatch
+  // means the slot was reused by a new texture, so the set is rewritten.
+  std::unordered_map<u32, CachedDescriptorSet> descriptorSets;
+
+  vk::UniquePipelineLayout pipelineLayout;
+  std::unique_ptr<GraphicsPipeline> graphicsPipeline;
+
+  std::array<std::unique_ptr<Buffer>, RenderContext::MAX_FRAMES_IN_FLIGHT>
+      instanceBuffers;
+  u32 frameIndex = 0;
+  u32 instanceCursor = 0;
+};
+
+}  // namespace sophia

engine/src/resources/mesh.cpp

@@ -1,39 +1,36 @@
-#include "mesh.hpp"
+#include "resources/mesh.hpp"
 
 #include <sophia/util/assert.hpp>
 #include <sophia/util/logger.hpp>
 
 namespace sophia {
 
-std::vector<vk::VertexInputBindingDescription>
+std::vector<vk::VertexInputBindingDescription> Mesh::getBindingDescriptions() {
-Mesh::Vertex::getBindingDescriptions() {
+  return {{0, sizeof(MeshVertex), vk::VertexInputRate::eVertex}};
-  std::vector<vk::VertexInputBindingDescription> bindingDescriptions(1);
-  bindingDescriptions[0].binding = 0;
-  bindingDescriptions[0].stride = sizeof(Vertex);
-  bindingDescriptions[0].inputRate = vk::VertexInputRate::eVertex;
-
-  return bindingDescriptions;
 }
 
 std::vector<vk::VertexInputAttributeDescription>
-Mesh::Vertex::getAttributeDescriptions() {
+Mesh::getAttributeDescriptions() {
-  std::vector<vk::VertexInputAttributeDescription> attributeDescriptions{};
+  return {
-
+      {0, 0, vk::Format::eR32G32B32Sfloat, offsetof(MeshVertex, position)},
-  attributeDescriptions.push_back(
+      {1, 0, vk::Format::eR32G32B32Sfloat, offsetof(MeshVertex, normal)},
-      {0, 0, vk::Format::eR32G32Sfloat, offsetof(Vertex, position)});
+      {2, 0, vk::Format::eR32G32Sfloat, offsetof(MeshVertex, uv)},
-  attributeDescriptions.push_back(
+      {3, 0, vk::Format::eR32G32B32A32Sfloat, offsetof(MeshVertex, color)},
-      {1, 0, vk::Format::eR32G32B32Sfloat, offsetof(Vertex, color)});
+  };
-  // attributeDescriptions.push_back(
-  //     {2, 0, vk::Format::eR32G32B32Sfloat, offsetof(Vertex, normal)});
-  // attributeDescriptions.push_back(
-  //     {3, 0, vk::Format::eR32G32Sfloat, offsetof(Vertex, uv)});
-
-  return attributeDescriptions;
 }
 
-Mesh::Mesh(Device& device, const Builder& builder) : device{device} {
+Mesh::Mesh(Device& device, const MeshData& data) : device{device} {
-  createVertexBuffers(builder.vertices);
+  if (!data.vertices.empty()) {
-  createIndexBuffers(builder.indices);
+    this->bounds = {data.vertices.front().position,
+                    data.vertices.front().position};
+    for (const MeshVertex& vertex : data.vertices) {
+      this->bounds.min = glm::min(this->bounds.min, vertex.position);
+      this->bounds.max = glm::max(this->bounds.max, vertex.position);
+    }
+  }
+
+  createVertexBuffers(data.vertices);
+  createIndexBuffers(data.indices);
 }
 
 Mesh::~Mesh() = default;
@@ -49,15 +46,17 @@ void Mesh::bind(vk::CommandBuffer commandBuffer) const {
   }
 }
 
-void Mesh::draw(vk::CommandBuffer commandBuffer) const {
+void Mesh::draw(vk::CommandBuffer commandBuffer, u32 instanceCount,
+                u32 firstInstance) const {
   if (this->hasIndexBuffer) {
-    commandBuffer.drawIndexed(this->indexCount, 1, 0, 0, 0);
+    commandBuffer.drawIndexed(this->indexCount, instanceCount, 0, 0,
+                              firstInstance);
   } else {
-    commandBuffer.draw(this->vertexCount, 1, 0, 0);
+    commandBuffer.draw(this->vertexCount, instanceCount, 0, firstInstance);
   }
 }
 
-void Mesh::createVertexBuffers(const std::vector<Vertex>& vertices) {
+void Mesh::createVertexBuffers(const std::vector<MeshVertex>& vertices) {
   this->vertexCount = static_cast<u32>(vertices.size());
   SOPHIA_ASSERT(this->vertexCount >= 3, "vertex count must be at least 3");
 

engine/src/resources/mesh.hpp

@@ -0,0 +1,53 @@
+#pragma once
+
+#include <memory>
+#include <sophia/aabb.hpp>
+#include <sophia/handles.hpp>
+#include <sophia/math.hpp>
+#include <sophia/mesh_data.hpp>
+#include <sophia/types.hpp>
+#include <vector>
+
+#include "vulkan/buffer.hpp"
+#include "vulkan/device.hpp"
+
+namespace sophia {
+
+class Mesh {
+ public:
+  // Binding 0 (per vertex, MeshVertex) for pipelines that draw meshes.
+  static std::vector<vk::VertexInputBindingDescription>
+  getBindingDescriptions();
+  static std::vector<vk::VertexInputAttributeDescription>
+  getAttributeDescriptions();
+
+  Mesh(Device& device, const MeshData& data);
+  ~Mesh();
+
+  Mesh(const Mesh&) = delete;
+  Mesh& operator=(const Mesh&) = delete;
+
+  // Bounds of the vertices, in the mesh's own space.
+  const AABB& getBounds() const { return this->bounds; }
+
+  void bind(vk::CommandBuffer commandBuffer) const;
+  void draw(vk::CommandBuffer commandBuffer, u32 instanceCount = 1,
+            u32 firstInstance = 0) const;
+
+ private:
+  void createVertexBuffers(const std::vector<MeshVertex>& vertices);
+  void createIndexBuffers(const std::vector<u32>& indices);
+
+  Device& device;
+
+  AABB bounds;
+
+  std::unique_ptr<Buffer> vertexBuffer;
+  u32 vertexCount;
+
+  bool hasIndexBuffer = false;
+  std::unique_ptr<Buffer> indexBuffer;
+  u32 indexCount;
+};
+
+}  // namespace sophia

engine/src/resources/pools/render_target_pool.cpp

@@ -0,0 +1,31 @@
+#include "resources/pools/render_target_pool.hpp"
+
+#include <tracy/Tracy.hpp>
+
+namespace sophia {
+
+RenderTargetPool::RenderTargetPool(Device& device, vk::Format format)
+    : device{device},
+      format{format},
+      // Depth-only formats, so the images have no stencil aspect to track.
+      depthFormat{device.findSupportedFormat(
+          {vk::Format::eD32Sfloat, vk::Format::eX8D24UnormPack32},
+          vk::ImageTiling::eOptimal,
+          vk::FormatFeatureFlagBits::eDepthStencilAttachment)} {}
+
+RenderTargetHandle RenderTargetPool::create(u32 width, u32 height) {
+  return pool.create(device, format, depthFormat, width, height);
+}
+
+void RenderTargetPool::release(RenderTargetHandle handle) {
+  SOPHIA_ASSERT(pool.isAlive(handle), "invalid RenderTargetHandle");
+  device.waitIdle();
+  pool.release(handle);
+}
+
+void RenderTargetPool::applyPendingResizes() {
+  ZoneScoped;
+  pool.forEach([](RenderTarget& target) { target.applyPendingResize(); });
+}
+
+}  // namespace sophia

engine/src/resources/pools/render_target_pool.hpp

@@ -0,0 +1,40 @@
+#pragma once
+
+#include <sophia/handles.hpp>
+#include <sophia/util/pool.hpp>
+
+#include "resources/render_target.hpp"
+#include "vulkan/device.hpp"
+
+namespace sophia {
+
+class RenderTargetPool {
+ public:
+  RenderTargetPool(Device& device, vk::Format format);
+
+  RenderTargetPool(const RenderTargetPool&) = delete;
+  RenderTargetPool& operator=(const RenderTargetPool&) = delete;
+
+  RenderTargetHandle create(u32 width, u32 height);
+  RenderTarget& get(RenderTargetHandle handle) { return pool.get(handle); }
+  const RenderTarget& get(RenderTargetHandle handle) const {
+    return pool.get(handle);
+  }
+  void release(RenderTargetHandle handle);
+
+  bool isAlive(RenderTargetHandle handle) const { return pool.isAlive(handle); }
+
+  vk::Format getFormat() const { return format; }
+  vk::Format getDepthFormat() const { return depthFormat; }
+
+  void applyPendingResizes();
+
+ private:
+  Device& device;
+  vk::Format format;
+  vk::Format depthFormat;
+
+  Pool<RenderTarget> pool{"RenderTarget"};
+};
+
+}  // namespace sophia

engine/src/resources/primitives.cpp

@@ -0,0 +1,55 @@
+#include <array>
+#include <sophia/primitives.hpp>
+
+namespace sophia::primitives {
+
+MeshData cube(float size, vec4 color) {
+  struct Face {
+    vec3 normal;
+    // Axes across the face, with u x v = normal, so corners taken
+    // counter-clockwise in (u, v) wind counter-clockwise seen from outside.
+    vec3 u;
+    vec3 v;
+  };
+
+  constexpr std::array<Face, 6> FACES{{
+      {{1.f, 0.f, 0.f}, {0.f, 0.f, -1.f}, {0.f, 1.f, 0.f}},
+      {{-1.f, 0.f, 0.f}, {0.f, 0.f, 1.f}, {0.f, 1.f, 0.f}},
+      {{0.f, 1.f, 0.f}, {1.f, 0.f, 0.f}, {0.f, 0.f, -1.f}},
+      {{0.f, -1.f, 0.f}, {1.f, 0.f, 0.f}, {0.f, 0.f, 1.f}},
+      {{0.f, 0.f, 1.f}, {1.f, 0.f, 0.f}, {0.f, 1.f, 0.f}},
+      {{0.f, 0.f, -1.f}, {-1.f, 0.f, 0.f}, {0.f, 1.f, 0.f}},
+  }};
+
+  constexpr std::array<vec2, 4> CORNERS{vec2{-1.f, -1.f}, vec2{1.f, -1.f},
+                                        vec2{1.f, 1.f}, vec2{-1.f, 1.f}};
+
+  float half = size / 2.f;
+
+  MeshData data;
+  data.vertices.reserve(FACES.size() * CORNERS.size());
+  data.indices.reserve(FACES.size() * 6);
+
+  for (const Face& face : FACES) {
+    auto base = static_cast<u32>(data.vertices.size());
+
+    for (vec2 corner : CORNERS) {
+      MeshVertex vertex;
+      vertex.position =
+          (face.normal + corner.x * face.u + corner.y * face.v) * half;
+      vertex.normal = face.normal;
+      // Texture v runs down while the face's v runs up.
+      vertex.uv = {(corner.x + 1.f) / 2.f, (1.f - corner.y) / 2.f};
+      vertex.color = color;
+      data.vertices.push_back(vertex);
+    }
+
+    for (u32 index : {0u, 1u, 2u, 2u, 3u, 0u}) {
+      data.indices.push_back(base + index);
+    }
+  }
+
+  return data;
+}
+
+}  // namespace sophia::primitives

engine/src/resources/render_target.cpp

@@ -0,0 +1,62 @@
+#include "resources/render_target.hpp"
+
+#include <algorithm>
+
+namespace sophia {
+
+RenderTarget::RenderTarget(Device& device, vk::Format format,
+                           vk::Format depthFormat, u32 width, u32 height)
+    : device{device}, format{format}, depthFormat{depthFormat} {
+  create(std::max(width, 1u), std::max(height, 1u));
+}
+
+RenderTarget::~RenderTarget() { destroy(); }
+
+vk::Extent2D RenderTarget::getExtent() const {
+  vk::Extent3D extent = this->image->getExtent();
+  return {extent.width, extent.height};
+}
+
+void RenderTarget::requestResize(u32 width, u32 height) {
+  this->pendingExtent = vk::Extent2D{std::max(width, 1u), std::max(height, 1u)};
+}
+
+void RenderTarget::applyPendingResize() {
+  if (!this->pendingExtent) {
+    return;
+  }
+
+  vk::Extent2D extent = *this->pendingExtent;
+  this->pendingExtent.reset();
+  if (extent == getExtent()) {
+    return;
+  }
+
+  this->device.waitIdle();
+
+  destroy();
+  create(extent.width, extent.height);
+}
+
+void RenderTarget::create(u32 width, u32 height) {
+  this->version++;
+  this->image = Image::Builder(this->device)
+                    .setExtent(width, height)
+                    .setFormat(this->format)
+                    .asColorAttachment()
+                    .withView()
+                    .build();
+  this->depthImage = Image::Builder(this->device)
+                         .setExtent(width, height)
+                         .asDepthAttachment()
+                         .setFormat(this->depthFormat)
+                         .withView()
+                         .build();
+}
+
+void RenderTarget::destroy() {
+  this->image.reset();
+  this->depthImage.reset();
+}
+
+}  // namespace sophia

engine/src/resources/render_target.hpp

@@ -0,0 +1,57 @@
+#pragma once
+
+#include <memory>
+#include <optional>
+#include <sophia/types.hpp>
+#include <vulkan/vulkan.hpp>
+
+#include "vulkan/device.hpp"
+#include "vulkan/image.hpp"
+
+namespace sophia {
+
+/**
+ * A place rendering can go: an offscreen color image, plus a depth image of
+ * the same size.
+ *
+ * Owned by the ResourceRegistry and addressed through a RenderTargetHandle.
+ */
+class RenderTarget {
+ public:
+  RenderTarget(Device& device, vk::Format format, vk::Format depthFormat,
+               u32 width, u32 height);
+  ~RenderTarget();
+
+  RenderTarget(const RenderTarget&) = delete;
+  RenderTarget& operator=(const RenderTarget&) = delete;
+
+  Image& getImage() const { return *this->image; }
+  Image& getDepthImage() const { return *this->depthImage; }
+
+  vk::Extent2D getExtent() const;
+  u32 getVersion() const { return this->version; }
+
+  void requestResize(u32 width, u32 height);
+
+  /**
+   * Applies a pending resize. Waits for the GPU, so it must run before any of
+   * the frame's work (or any UI reference to the image) is recorded.
+   */
+  void applyPendingResize();
+
+ private:
+  void create(u32 width, u32 height);
+  void destroy();
+
+  Device& device;
+  vk::Format format;
+  vk::Format depthFormat;
+
+  std::unique_ptr<Image> image;
+  std::unique_ptr<Image> depthImage;
+
+  std::optional<vk::Extent2D> pendingExtent;
+  u32 version = 0;
+};
+
+}  // namespace sophia

engine/src/resources/resource_registry.hpp

@@ -0,0 +1,36 @@
+#pragma once
+
+#include <array>
+#include <sophia/handles.hpp>
+#include <sophia/util/pool.hpp>
+
+#include "resources/mesh.hpp"
+#include "resources/pools/render_target_pool.hpp"
+#include "resources/texture.hpp"
+#include "vulkan/device.hpp"
+
+namespace sophia {
+
+class ResourceRegistry {
+ public:
+  ResourceRegistry(const ResourceRegistry&) = delete;
+  ResourceRegistry& operator=(const ResourceRegistry&) = delete;
+
+  ResourceRegistry(Device& device, vk::Format renderTargetFormat)
+      : device{device}, renderTargetPool{device, renderTargetFormat} {
+    constexpr std::array<u8, 4> WHITE{0xFF, 0xFF, 0xFF, 0xFF};
+    whiteTexture = texturePool.create(device, 1, 1, WHITE);
+  }
+
+  Device& device;
+  Pool<Mesh> meshPool{"Mesh"};
+  RenderTargetPool renderTargetPool;
+  Pool<Texture> texturePool{"Texture"};
+  // MaterialPool materials;
+
+  // 1x1 white. Stands in for sprites without a texture, so they draw as a
+  // solid quad in their tint color.
+  TextureHandle whiteTexture = INVALID_HANDLE;
+};
+
+}  // namespace sophia

engine/src/resources/resource_registry_ref.cpp

@@ -0,0 +1,111 @@
+#include <stb_image.h>
+
+#include <sophia/resource_registry_ref.hpp>
+#include <sophia/util/assert.hpp>
+#include <sophia/util/logger.hpp>
+#include <stdexcept>
+
+#include "resources/resource_registry.hpp"
+
+namespace sophia {
+
+template <>
+MeshHandle ResourceRegistryRef::load<Mesh>(const std::string& path) {
+  (void)path;
+  SOPHIA_ASSERT(false,
+                "Mesh::load(path) is not implemented yet - no model file "
+                "format is supported; build a MeshData instead");
+  return MeshHandle{};
+}
+
+template <>
+TextureHandle ResourceRegistryRef::load<Texture>(const std::string& path) {
+  int width = 0;
+  int height = 0;
+  int channels = 0;
+  // Always decode to RGBA8, whatever the file has.
+  stbi_uc* pixels = stbi_load(path.c_str(), &width, &height, &channels, 4);
+  if (pixels == nullptr) {
+    log::fatal("failed to load texture {} - {}", path, stbi_failure_reason());
+    throw std::runtime_error("failed to load texture: " + path);
+  }
+
+  auto size = static_cast<size_t>(width) * static_cast<size_t>(height) * 4;
+  TextureHandle handle = registry->texturePool.create(
+      registry->device, static_cast<u32>(width), static_cast<u32>(height),
+      std::span<const u8>{pixels, size});
+  stbi_image_free(pixels);
+  return handle;
+}
+
+template <>
+void ResourceRegistryRef::release<Mesh>(MeshHandle handle) {
+  // Frames in flight may still be drawing it.
+  registry->device.waitIdle();
+  registry->meshPool.release(handle);
+}
+
+template <>
+void ResourceRegistryRef::release<RenderTarget>(RenderTargetHandle handle) {
+  registry->renderTargetPool.release(handle);
+}
+
+template <>
+void ResourceRegistryRef::release<Texture>(TextureHandle handle) {
+  SOPHIA_ASSERT(handle != registry->whiteTexture,
+                "the built-in white texture cannot be released");
+  // Frames in flight may still be sampling it.
+  registry->device.waitIdle();
+  registry->texturePool.release(handle);
+}
+
+MeshHandle ResourceRegistryRef::createResource(std::type_identity<Mesh>,
+                                               const MeshData& data) {
+  return registry->meshPool.create(registry->device, data);
+}
+
+RenderTargetHandle ResourceRegistryRef::createResource(
+    std::type_identity<RenderTarget>, u32 width, u32 height) {
+  return registry->renderTargetPool.create(width, height);
+}
+
+TextureHandle ResourceRegistryRef::createResource(std::type_identity<Texture>,
+                                                  u32 width, u32 height,
+                                                  std::vector<u8> pixels) {
+  return registry->texturePool.create(registry->device, width, height,
+                                      std::span<const u8>{pixels});
+}
+
+void ResourceRegistryRef::requestResize(RenderTargetHandle handle, u32 width,
+                                        u32 height) {
+  registry->renderTargetPool.get(handle).requestResize(width, height);
+}
+
+glm::vec2 ResourceRegistryRef::getExtent(RenderTargetHandle handle) const {
+  vk::Extent2D extent = registry->renderTargetPool.get(handle).getExtent();
+  return {static_cast<float>(extent.width), static_cast<float>(extent.height)};
+}
+
+AABB ResourceRegistryRef::getBounds(MeshHandle handle) const {
+  return registry->meshPool.get(handle).getBounds();
+}
+
+bool ResourceRegistryRef::isAlive(MeshHandle handle) const {
+  return registry->meshPool.isAlive(handle);
+}
+
+bool ResourceRegistryRef::isAlive(RenderTargetHandle handle) const {
+  return registry->renderTargetPool.isAlive(handle);
+}
+
+glm::vec2 ResourceRegistryRef::getExtent(TextureHandle handle) const {
+  const Texture& texture = registry->texturePool.get(handle);
+  return {static_cast<float>(texture.getWidth()),
+          static_cast<float>(texture.getHeight())};
+}
+
+bool ResourceRegistryRef::isAlive(TextureHandle handle) const {
+  return registry->texturePool.isAlive(handle);
+}
+
+}  // namespace sophia

engine/src/resources/texture.cpp

@@ -0,0 +1,32 @@
+#include "resources/texture.hpp"
+
+#include <sophia/util/assert.hpp>
+#include <sophia/util/logger.hpp>
+
+namespace sophia {
+
+Texture::Texture(Device& device, u32 width, u32 height,
+                 std::span<const u8> pixels) {
+  SOPHIA_ASSERT(width > 0 && height > 0, "texture must not be empty");
+  SOPHIA_ASSERT(pixels.size() == static_cast<size_t>(width) * height * 4,
+                "texture pixel data must be width * height RGBA8 texels");
+
+  this->image = Image::Builder(device)
+                    .setExtent(width, height)
+                    .setFormat(vk::Format::eR8G8B8A8Srgb)
+                    .setUsage(vk::ImageUsageFlagBits::eSampled)
+                    .setInitialData(pixels.data(), pixels.size())
+                    .withView()
+                    .withSampler(vk::Filter::eLinear,
+                                 vk::SamplerAddressMode::eClampToEdge)
+                    .build();
+}
+
+Texture::~Texture() { log::trace("destroyed sophia::Texture"); }
+
+vk::DescriptorImageInfo Texture::descriptorInfo() const {
+  return {this->image->getSampler(), this->image->getView(),
+          vk::ImageLayout::eShaderReadOnlyOptimal};
+}
+
+}  // namespace sophia

engine/src/resources/texture.hpp

@@ -0,0 +1,38 @@
+#pragma once
+
+#include <memory>
+#include <sophia/types.hpp>
+#include <span>
+#include <vulkan/vulkan.hpp>
+
+#include "vulkan/device.hpp"
+#include "vulkan/image.hpp"
+
+namespace sophia {
+
+/**
+ * A sampled, read-only RGBA8 (sRGB) image.
+ *
+ * Owned by the ResourceRegistry and addressed through a TextureHandle.
+ */
+class Texture {
+ public:
+  /** `pixels` is width * height tightly packed RGBA8 texels, top row first. */
+  Texture(Device& device, u32 width, u32 height, std::span<const u8> pixels);
+  ~Texture();
+
+  Texture(const Texture&) = delete;
+  Texture& operator=(const Texture&) = delete;
+
+  const Image& getImage() const { return *this->image; }
+
+  u32 getWidth() const { return this->image->getExtent().width; }
+  u32 getHeight() const { return this->image->getExtent().height; }
+
+  vk::DescriptorImageInfo descriptorInfo() const;
+
+ private:
+  std::unique_ptr<Image> image;
+};
+
+}  // namespace sophia

engine/src/scene.cpp

@@ -1,17 +0,0 @@
-#include "scene.hpp"
-
-#include <sophia/components.hpp>
-#include <sophia/util/logger.hpp>
-
-namespace sophia {
-
-Scene::Scene() {
-  entt::entity entity = this->registry.create();
-
-  auto& a = this->registry.emplace<TransformComponent>(entity);
-  auto& b = this->registry.get<TransformComponent>(entity);
-}
-
-Scene::~Scene() { log::trace("destroying sophia::Scene"); }
-
-}  // namespace sophia

engine/src/scene.hpp

@@ -1,16 +0,0 @@
-#pragma once
-
-#include <entt/entt.hpp>
-
-namespace sophia {
-
-class Scene {
- public:
-  Scene();
-  ~Scene();
-
- private:
-  entt::registry registry;
-};
-
-}  // namespace sophia

engine/src/scene/entity.cpp

@@ -0,0 +1,8 @@
+#include <sophia/entity.hpp>
+
+namespace sophia {
+
+Entity::Entity(entt::entity handle, Scene* scene)
+    : handle(handle), scene(scene) {}
+
+}  // namespace sophia