Support vertex pulling #16826
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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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. |
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I've updated the PR with:
I'm not sure if the way I did this is okay but it seems to work. |
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Ah, looks like the index buffer in my test is being created as a Uint16Array and WGSL only supports u32 as a type... |
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Okay, I've added support for 16-bit and 32-bit indices as well as non-indexed geometry. |
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Here's how I would do it: master...Popov72:Babylon.js:MiiBond-mbond/support-vertex-pulling Basically, I moved your code to To avoid running the code on every draw call and impacting performance, I exit early if the vertex pulling parameter (true/false) is the same as the previous call. This means we don't automatically handle a change in the vertex buffer list or if the index buffer changes after the first draw of the mesh. I don't think this is a problem, though, as it's unlikely that we'll need to add/remove a vertex buffer after displaying the mesh (we can still update a buffer). Let's see if anyone complains about this, and we'll take action if necessary. cc @sebavan [EDIT] I replaced the uniforms by defines, because it's unlikely the value of these uniforms will ever change once we set a value. That way, we won't pay for additional cost associated to them. The updated PG: |
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Thanks a ton, @Popov72! That looks way cleaner. I've merged your changes in. |
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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#131 For vertex pulling to work, we typically need: 1. An empty vertex layout. 2. Our needed vertex buffers assigned as storage buffers 3. A non-indexed draw call with the number of vertices to process. This causes `@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.drawArraysType` even though the mesh has indices. To do this, we set `material.useVertexPulling`. The shader must also _not_ declare vertex attributes. --------- Co-authored-by: Popov72 <[email protected]>
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#131
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. To do this, we setmaterial.useVertexPulling.The shader must also not declare vertex attributes.