Mesh shader support

[rishflab]

Apple just announced mesh shader support for the upcoming metal 3.0 release and Khronos is working on adding it to Vulkan (taking their sweet time). Directx12 has supported it for a while now. With the three big players and general industry consensus moving towards a mesh shader future, can we get mesh shader support in webgpu?

From what I have gathered, mesh shading is a pretty big paradigm shift, comparable to opengl 2.0 -> opengl 3.3. I think webgpu needs needs to keep up these shifts otherwise it ends up going the way of webgl. This is not a bad thing per say as webgl has seen heaps of use, but people revert back to native API's when they want to do anything serious.

[Kangz]

With all three target APIs supporting mesh shaders in some form, adding them to WebGPU definitely seems more doable. However at the point the group is focusing on finishing a v1 that supports a very wide range of hardware, some of which doesn't have mesh shaders. My understanding is also that some mobile GPUs just can't support mesh shaders due to hardware limitations so we'll have to be careful about that.

Tagging post-V1. To make progress on this we'll also need a pretty exhaustive comparison of mesh shaders between the three APIs so that we can come up with a tentative design for WebGPU (maybe bonus points if it can be emulated with compute shaders running before the render pass? Not sure).

For cross linking: mesh shading is also mentioned in #445

[rishflab]

maybe bonus points if it can be emulated with compute shaders running before the render pass? Not sure).

I am looking into this currently. Some potentially useful articles I have come across:
https://timur.hu/blog/2022/how-mesh-shaders-are-implemented
https://tellusim.com/mesh-shader-emulation/

[alienself]

Would absolutely love to see support for Mesh shader in WebGPU.
It would be a game changer for many advanced use cases.

[heavyrain266]

Mesh shaders are needed for e.g. PSSL in order to run native Game Engines based on WebGPU. PlayStation 5 uses mesh shaders in PSSL which makes it hard to maintain custom backend because of need to force usage of PSSL and rewrite of all the shaders using it.

[kainino0x]

This blog post series should be very helpful - it covers mesh shaders on all of D3D12, Metal, and Vulkan:
https://chaoticbob.github.io/2024/01/24/mesh-shading-part-1.html