Support cluster acceleration structure builds in slang-rhi

[dlacewellNV]

Shading intrinsics for cluster geometry were added to Slang in shader-slang/slang#7028.
Now we need a way to build cluster acceleration structures (CLASes) in slang-rhi.
This is supported in OptiX 9.0, or with an extension/NVAPI for Vulkan/DX.

OptiX >= 9.0:

optixClusterAccelBuild
optixClusterAccelComputeMemoryUsage

This is an indirect build; it is a host call but some arguments are passed in device memory. There are new OptiX data types to support this.

The pipeline flag OptixPipelineCompileOptions::allowClusteredGeometry must be set to enable clusters during traversal.

Use optixDeviceContextGetProperty with OPTIX_DEVICE_PROPERTY_CLUSTER_ACCEL to check whether the cluster API is supported on a given device.

See the Clusters section of the programming guide for more details:
https://raytracing-docs.nvidia.com/optix9/guide/index.html#acceleration_structures#clusters

NVAPI

NvAPI_D3D12_RaytracingExecuteMultiIndirectClusterOperation
(and many supporting indirect data structures)

Vulkan extension

VK_NV_cluster_acceleration_structure

[jkwak-work]

@dlacewellNV , can you give us a way to verify the functionality when we are done implementing it.
Please share any example code that we can use for the verification purpose so that we can start with a clear goal of when the task is done.

[dlacewellNV]

Hi @jkwak-work . There is no existing slang-rhi sample, we'd need to write that as part of this task. However, there are existing samples that directly use OptiX/DX/Vk.

There is one called optixClusterUnstructuredMesh in the OptiX 9.0 SDK. You'll need to download the SDK and install it.
https://developer.nvidia.com/designworks/optix/download

Also several Vulkan samples; I am less familiar with these but the first one for "animated clusters" looks like the simplest:
https://developer.nvidia.com/blog/nvidia-rtx-mega-geometry-now-available-with-new-vulkan-samples/

This blog post has some more context as well:
https://developer.nvidia.com/blog/fast-ray-tracing-of-dynamic-scenes-using-nvidia-optix-9-and-nvidia-rtx-mega-geometry/

[skallweitNV]

@dlacewellNV has added initial support for clusters on OptiX in #575

I've improved on the initial implementation:

• refactor slang-rhi API to align it better to D3D12/Vulkan in Cluster API refactor #586
• add Vulkan support in Cluster API support for Vulkan #587
• add D3D12 support in Cluster API support for D3D12 #588

[szihs]

@skallweitNV did we get everything merged for this one?

[skallweitNV]

Yes, I'm closing this.