Mesh Shaders Tracking Issue

[inner-daemons]

Replaces #3018.

Spec

Progress

Current open PR(s) and other work

Remaining work

• Mesh shader indirect validation #9124
• Mesh shader *indices validation #8878
• Mesh shader redesign #9170
• Add robust testing of mesh shader related parsing and validation errors #8517
• SPIR-V mesh shader parser #9171

naga

• Add mesh, task shaders to naga shader types so wgpu-hal can stop pretending they are compute shaders - Add mesh shader stages to wgt::ShaderStages and naga::ShaderStage #7292
• Support in WGSL frontend - WGSL parsing for mesh shaders #8370
• Add robust testing of mesh shader related parsing and validation errors #8517
• Validation - New mesh shader limits #8507
• Support in SPIRV writer - Naga mesh shader SPIR-V writer #8456
• Support in HLSL writer - Mesh shader HLSL writer #8752
• Support in MSL writer - Mesh shaders MSL writer #8739
• Support in WGSL regurgitator - Naga mesh shader WGSL writer #8481
• SPIR-V mesh shader parser #9171
• Reflection info for pipeline validation - New mesh shader limits #8507
• Restrict builtins in mesh shader outputs #8360
• Limit task shader generated workgroup size #8746

wgpu-hal backends

• Vulkan - Mesh shaders - initial wgpu hal changes #7089
• DX12 - Mesh Shading for DirectX 12 #7219 ([hal/dx12] Mesh Shaders #8110) - still needs naga support
• Metal - [hal/metal] Mesh Shaders #8139 - naga PR separate

Other

• Mesh shader redesign #9170
• Formal spec - Added mesh shading spec #7885
• wgpu API - Add mesh shading api to wgpu & wgpu-core #7345
• wgpu-core pipeline validation - Add mesh shading api to wgpu & wgpu-core #7345 (?)
• Limits & validation of mesh and task shader interface in wgpu-core #8003 - New mesh shader limits #8507
• General tests- Add mesh shading api to wgpu & wgpu-core #7345
• Add robust testing of mesh shader related parsing and validation errors #8517
• Examples - Add mesh shading api to wgpu & wgpu-core #7345
• Fate of EXPERIMENTAL_MESH_SHADER_MULTIVIEW #8343
• Ray queries in mesh shaders #8753
• Speed up zero initialization of workgroup memory #4592 - deprecated by Mesh shader redesign #9170

Features

• Multiview mesh shaders #7262
• Primitive ID builtin - not supported in wgpu in general yet - Support enable primitive-index; in WGSL #8236 required
• Queries - Mesh shader queries #8523 (unplanned)
• Point primitives(at least in vulkan, probably its own feature)
• Finalize limits - Limits & validation of mesh and task shader interface in wgpu-core #8003 - New mesh shader limits #8507

Bugs

• SPIR-V writing for mesh shaders is broken on llvmpipe #8727
• Naga spir-v and msl output has divergent return statements in entry points #8738
• Task shader payloads are not zero initialized #8744
• Mesh shader *indices validation #8878
• Various SPIR-V fixes for mesh shaders #8756
• Mesh shader indirect validation #9124

Issues to work out

• How to implement multiview, what features, etc
• Queries

[inner-daemons]

@cwfitzgerald
I’ve been thinking, we probably ought to have some way to indicate the “payload” for task and mesh shaders. I’m updating the original comment to add an attribute, @payload(some global variable). This would also probably mean we don’t need a new storage class. Let me know if you think there is a better option.

[cwfitzgerald]

Sounds fine - one thing to keep in mind that we want the IR to be compatible enough with how SPIR-V does stuff, such that spirv-in can eventually support mesh shaders. I don't know specifics about how mesh shaders work in spirv, but we should be careful to not require things that are too hard to implement in that frrontend. We' already require heroics in the spirv frontend for atomics.

[inner-daemons]

@cwfitzgerald Thanks for the response. I'll try to keep a list of things that might be hard to implement in certain environments.