Basic Ray Traced Reflections with DXR

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Overview

• Add raytracing pipeline abstraction to RHI (DXR only; Vulkan backend is really getting left behind even more :sob:)
• Recreate BLASes if needed. (ex: a new static mesh is added to the scene)
• Update instance transforms of BLASes every frame for animated meshes. (keep BLAS geometries and only recreate TLAS)
• Implement basic RTR. For each screen pixel which belongs to some surface, shoot a ray from the surface toward its normal. If another surface hits, reconstruct its material data from closest hit shader using global vertex/index buffers, bindless material SRVs/CBVs, and gpuScene representation. Shading calculation is simply one-bounce perfect specular reflection without considering NDF but I'm just practicing DXR here. Advanced shading can wait.

Getting DXR operates is OK-ish, now I have to do huge refactoring.

• [x] Manage bindless materials from GPUScene, not BasePass.
• [x] Manage global descriptor heaps in another manager? I'm abusing TextureManager for all descriptor allocations.

Diff is getting way too big. Stop here and do remaining works in master.

TODO

• Cleanup buffer abstraction classes. Got really messy.
• Update a BLAS instance transform only if its corresponding static mesh is animating.

Demo scene

Crumpled geometries test

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References from an old note

DXR setup

• https://developer.nvidia.com/rtx/raytracing/dxr/DX12-Raytracing-tutorial-Part-2
• https://therealmjp.github.io/posts/dxil-linking/

RTR

• Performant Reflective Beauty: Hybrid Raytracing with Far Cry 6