WIP - Support vertex pulling #16826
WIP - Support vertex pulling #16826
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Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s). |
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Visualization tests for WebGPU |
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WebGL2 visualization test reporter: |
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It would be a great feature to have! However, I think we should strive to improve integration into the engine so that we/the user don't have to manually manage storage buffers and so that it remains as transparent as possible.
I wonder if we could just create the vertex buffers with STORAGE flags (in addition to the VERTEX + WRITE flags we currently use)... This way, the buffers should be usable in both pulling and non-pulling modes (to be tested, however, and I don't know if adding unnecessary flags has an impact on performance - STORAGE is not necessary in non-pulling mode, and VERTEX is not necessary in pulling mode). In this case, we could add a I'm probably missing a few things, but I think this would be a better way to support this mode. cc @sebavan for the discussion. |
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Also, in your PG example, I think you would want to calculate the normal yourself by performing the vector product of two edges of the triangle, because the normal to a vertex is generally the average of the normals of the faces to which that vertex belongs, so it is not the true normal to the face. |
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I really like where it is going :-) and I ll chat with Mike after his break. |
Vertex pulling is where you do your own reading of vertex data in the vertex shader instead of relying on the standard vertex attribute pipeline. I'm not sure of the best approach in Babylon but I made some minimal changes to make it work. I'd appreciate some feedback and ideas for a better way to set this up.
First, some motivation:
I want vertex pulling as a way of selecting vertex data from neighboring vertices in the IBL Shadows voxelization shader. By retrieving normal info for the provoking vertex of a triangle, I can selectively swizzle the axes of the position to maximize rasterization area and avoid missing voxels. This eliminates the need for 3-pass voxelization and opens the door for doing realtime voxelization of animated geometry (in WebGPU only due to the need for 3D storage textures).
https://playground.babylonjs.com/?snapshot=refs/pull/16826/merge#XSNYAU#124
For vertex pulling to work, we typically need:
@builtin(vertex_index)to be sequential which is critical for fetching info about neighboring vertices.No changes are needed to Babylon for the first two requirements. For the 3rd point though, we want to do a
engine.drawArraysTypeeven though the mesh has indices. We could mark a mesh asmesh.isUnIndexed = truebut then the draw call uses the number of vertices in the geometry and not the number of indices. Another issue is that we don't really want to modify the mesh at all since some render passes won't do vertex pulling. Perhaps a better solution is to do something akin tort.setMaterialForRenderingso that vertex pulling can be enabled per-render pass?e.g.
rt.enableVertexPulling(mesh, true);Thoughts?