Adding in simple alpha blending

engine/src/vulkan/pipelines/graphics_pipeline.cpp

@@ -95,6 +95,12 @@ GraphicsPipeline::Builder& GraphicsPipeline::Builder::setVertexInput(
   return *this;
 }
 
+GraphicsPipeline::Builder& GraphicsPipeline::Builder::setAlphaBlending(
+    bool enabled) {
+  this->alphaBlending = enabled;
+  return *this;
+}
+
 std::unique_ptr<GraphicsPipeline> GraphicsPipeline::Builder::build() const {
   if (this->vertexShader == nullptr || this->fragmentShader == nullptr) {
     log::fatal(
@@ -128,7 +134,8 @@ std::unique_ptr<GraphicsPipeline> GraphicsPipeline::Builder::build() const {
       this->device, *this->vertexShader, *this->fragmentShader,
       this->pipelineLayout, this->colorAttachmentFormats,
       this->depthAttachmentFormat, this->stencilAttachmentFormat,
-      this->bindingDescriptions, this->attributeDescriptions));
+      this->bindingDescriptions, this->attributeDescriptions,
+      this->alphaBlending));
 }
 
 GraphicsPipeline::GraphicsPipeline(
@@ -137,10 +144,21 @@ GraphicsPipeline::GraphicsPipeline(
     std::vector<vk::Format> colorAttachmentFormats,
     vk::Format depthAttachmentFormat, vk::Format stencilAttachmentFormat,
     std::vector<vk::VertexInputBindingDescription> bindingDescriptions,
-    std::vector<vk::VertexInputAttributeDescription> attributeDescriptions)
+    std::vector<vk::VertexInputAttributeDescription> attributeDescriptions,
+    bool alphaBlending)
     : Pipeline(device, vk::PipelineBindPoint::eGraphics) {
   setDefaultGraphicsPipelineConfig();
 
+  if (alphaBlending) {
+    vk::PipelineColorBlendAttachmentState& blend =
+        this->config.colorBlendAttachment;
+    blend.blendEnable = vk::True;
+    blend.srcColorBlendFactor = vk::BlendFactor::eSrcAlpha;
+    blend.dstColorBlendFactor = vk::BlendFactor::eOneMinusSrcAlpha;
+    blend.srcAlphaBlendFactor = vk::BlendFactor::eOne;
+    blend.dstAlphaBlendFactor = vk::BlendFactor::eOneMinusSrcAlpha;
+  }
+
   this->config.bindingDescriptions = std::move(bindingDescriptions);
   this->config.attributeDescriptions = std::move(attributeDescriptions);
   this->config.pipelineLayout = pipelineLayout;

engine/src/vulkan/pipelines/graphics_pipeline.hpp

@@ -47,7 +47,8 @@ class GraphicsPipeline : public Pipeline {
       std::vector<vk::Format> colorAttachmentFormats,
       vk::Format depthAttachmentFormat, vk::Format stencilAttachmentFormat,
       std::vector<vk::VertexInputBindingDescription> bindingDescriptions,
-      std::vector<vk::VertexInputAttributeDescription> attributeDescriptions);
+      std::vector<vk::VertexInputAttributeDescription> attributeDescriptions,
+      bool alphaBlending);
 
   void setDefaultGraphicsPipelineConfig();
 
@@ -69,6 +70,8 @@ class GraphicsPipeline::Builder {
   Builder& setVertexInput(
       std::vector<vk::VertexInputBindingDescription> bindingDescriptions,
       std::vector<vk::VertexInputAttributeDescription> attributeDescriptions);
+  // Straight (non-premultiplied) "over" blending on every color attachment.
+  Builder& setAlphaBlending(bool enabled = true);
 
   std::unique_ptr<GraphicsPipeline> build() const;
 
@@ -83,6 +86,7 @@ class GraphicsPipeline::Builder {
   vk::Format stencilAttachmentFormat = vk::Format::eUndefined;
   std::vector<vk::VertexInputBindingDescription> bindingDescriptions{};
   std::vector<vk::VertexInputAttributeDescription> attributeDescriptions{};
+  bool alphaBlending = false;
 };
 
 }  // namespace sophia