D3D12 Backend

[redorav]

There are several fundamental tasks missing

• D3D12 shader reflection in CrShaderCompiler
• Root Signature Management - put as binaries in custom shaders (needs reworking to account for platforms that need to compile the root signature into the shader)
• Shaders
• Fences
• Pipelines
• Swapchain
• Command Buffer
• Textures
• Texture Loading: we need a better API
• Resource Binding: Constant Buffers, Textures, Samplers, etc -> both graphics and compute
• Buffers
• Features
• Resource transitions (halfway there)
• Caching (root signatures, descriptor heaps, primitive topology, etc)
• Pipeline Cache storage and loading

Requirements for descriptor heaps

1. Non-shader-visible descriptor heap that I can return and reuse descriptors. A pool

2. Shader-visible stream of descriptors. Command buffers reserve chunk of descriptors as they need them (this is the only sync point) and use those throughout the frame. Those chunks are reserved for the duration of the frame but reused later