Ray Tracing Pipeline (KHR)

[ComfyFluffy]

1. Update documentation to reflect any user-facing changes - in this repository.

2. Make sure that the changes are covered by unit-tests.

3. Run cargo clippy on the changes.

4. Run cargo +nightly fmt on the changes.

5. Please put changelog entries in the description of this Pull Request
   if knowledge of this change could be valuable to users. No need to put the
   entries to the changelog directly, they will be transferred to the changelog
   file by maintainers right after the Pull Request merge.

Changelog:

### Additions
- Support for the `VK_KHR_ray_tracing_pipeline`.

Changes

• New struct RayTracingPipeline, which corresponds to the vkPipeline object and construction methods and structs.
• bind_pipeline_ray_tracing & trace_rays (vkCmdTraceRaysKHR) in the old and new sync.
• Device::get_ray_tracing_shader_group_handles. Used in building the shader binding table.
• ShaderGroupHandlesData. Helper for the data from get_ray_tracing_shader_group_handles.
• ShaderBindingTable. Struct that holds the addresses and underlying buffer of shader binding table, which is used in trace_rays. It contains a constructor that automatically build the SBT from pipeline groups.
• Examples: triangle-raytracing-auto for the old AutoCommandBuffer, and triangle-raytracing for the new taskgraph sync.

Not implemented (yet) in this PR

• DeferredOperationKHR. Not planned.
• RayTracingCaptureReplay. Not planned.
• RayTracingPipelineStackSize (in dynamic stats). Maybe in this PR?

[ComfyFluffy]

Finally a working example with vulkano-taskgraph. The next step is to test with AutoCommandBuffer.

[ComfyFluffy]

I have done the major changes and the PR should be ready for review. I will add some description in PR page and maybe some unit tests soon.

[marc0246]

Please name the examples just "ray-tracing." Most of the examples render a triangle but they do it with more advanced features than just a hello triangle.

[Rua]

This looks good so far, and runs correctly on my machine. I left some comments on individual places that need attention.

In addition, I think there should be some documentation for the ray tracing pipeline module itself. It should explain some of the basics of how ray tracing pipelines work, and a summary of the different shader types and their roles.

[marc0246]

As a sidenote @ComfyFluffy, to help you with development in the future: I saw that you were debugging by adding a debug messenger to some examples. There's no need to do that; you should instead use vkconfig. It can inject validation layers into any existing Vulkan application (including our examples).

[mirage2032]

Hi, any idea how long until it gets merged?

[Rua]

When it's done?

[ComfyFluffy]

As a sidenote @ComfyFluffy, to help you with development in the future: I saw that you were debugging by adding a debug messenger to some examples. There's no need to do that; you should instead use vkconfig. It can inject validation layers into any existing Vulkan application (including our examples).

That's helpful! Thank you.

[Rua]

Some more public items in pipeline/ray_tracing.rs are still missing documentation.

[ComfyFluffy]

A question: how should we deal with ash::vk::StridedDeviceAddressRegionKHR? Should we create a corresponding Vulkano type, or maybe pub use it in src/lib.rs?

[Rua]

Vulkano generally defines all its structs itself. That way we can add methods and traits to them, independent of the Ash implementation.

[ComfyFluffy]

Vulkano generally defines all its structs itself. That way we can add methods and traits to them, independent of the Ash implementation.

I have added a struct definition for StridedDeviceAddressRegion in lib.rs.

[Rua]

Thank you so much for your PR and your patience in dealing with my nitpicks!

[marc0246]

Thank you @ComfyFluffy for finally bringing us this long-awaited feature! We all love you for it ❤️