Descriptors and pipelines

VulkanBase is the shared foundation for compute and graphics pipelines. It creates descriptor set layouts, descriptor pools, descriptor sets, pipeline layouts, and shader modules.

Declare bindings

Derived workloads implement GetBindingInfo() and return one BindingInfo per shader binding:

std::vector<core::vulkan::BindingInfo> GetBindingInfo() const override {
  return {
      {0, VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER,
       VK_SHADER_STAGE_COMPUTE_BIT},
      {1, VK_DESCRIPTOR_TYPE_STORAGE_BUFFER,
       VK_SHADER_STAGE_COMPUTE_BIT},
  };
}

Write descriptors

After the base initialization, derived classes use the protected helpers for uniform buffers, storage buffers, and combined image samplers. Finish by calling vkUpdateDescriptorSets() with the writes assembled by those helpers.

void MyComputePipeline::Init() {
  core::vulkan::VulkanCompute::Init();

  CreateUniformBufferDescriptorSet(0, uniform_buffer_);
  CreateStorageBufferDescriptorSet(1, input_buffer_);
  CreateStorageBufferDescriptorSet(2, output_buffer_);

  vkUpdateDescriptorSets(
      context_->logical_device,
      static_cast<uint32_t>(writes_.size()), writes_.data(),
      0, nullptr);
}

The sequence matters: the base Init() creates the descriptor layout, pool, set, pipeline layout, and concrete pipeline. The descriptor helper calls then fill the writes for that allocated set.

Bind before dispatch or draw

vkCmdBindPipeline(
    command_buffer, VK_PIPELINE_BIND_POINT_COMPUTE, pipeline);
vkCmdBindDescriptorSets(
    command_buffer, VK_PIPELINE_BIND_POINT_COMPUTE,
    pipeline_layout, 0, 1, &descriptor_set_, 0, nullptr);

Use VK_PIPELINE_BIND_POINT_GRAPHICS for a VulkanRender subclass.

Warning

The binding numbers, descriptor types, and shader stages returned by GetBindingInfo() must match the shader declarations exactly. Also create one descriptor write for every declared binding before calling vkUpdateDescriptorSets(); the base class sizes its internal arrays from that declaration.

Specialize the pipeline

• Derive from VulkanCompute for one compute shader and a compute pipeline.

• Derive from VulkanRender for vertex and fragment shaders and a graphics pipeline.

Both base classes expect the application-specific subclass to provide shader code and binding declarations.

Pipeline objects and their descriptor resources are destroyed by VulkanBase. The buffers, image views, and samplers referenced by a descriptor remain owned by the application and must stay alive while submitted commands can access them.