Autodesk: Skip use of geometry shader for patch tessellation when possible #3422
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Filed as internal issue #USD-10438 |
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/AzurePipelines run |
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Exciting! |
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I don't think the TfDebug code introduced here is needed. It matches existing functionality provided by TF_DEBUG=HDST_DUMP_GLSLFX_CONFIG |
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@davidgyu PR has been updated based on this feedback. |
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/AzurePipelines run |
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Azure Pipelines successfully started running 1 pipeline(s). |
| uint8_t tesIndex = 0; | ||
| TES[tesIndex++] = _tokens->instancing; | ||
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| if (geomStyle == HdMeshGeomStyleEdgeOnSurf) { |
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This seems not quite right. Minimally, this should also test hasBuiltinBarycentrics, which is the only thing that edges need from GS.
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Ah, right, when the fragment shader has barycentrics, it can render edges.
| vec2 t1 = HdGet_st(i1); | ||
| vec2 t2 = HdGet_st(i2); | ||
| vec2 t3 = HdGet_st(i3); | ||
| vec2 t = InterpolatePrimvar(t0, t1, t2, t3, basis, uv); |
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The signal driving displacement might not be named st, e.g. an asset like usdImagingGL/testenv/testUsdImagingGLDisplacement/testUsdImagingGLDisplacement.usda will fail during shader compilation since the displacement input coord is named st_faceVarying.
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I see. I'm not quite sure what a comprehensive solution would look like. Will have to think about that.
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Yeah, that part of the codeGen texture accessors is delicate. I've been looking into refactoring the displacement terminal a little differently than you have here and I'll tty to share that back with you (possibly next week).
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That will help, thanks. I appreciate that.
Description of Change(s)
This updates the shader configuration for surface patches, for better performance. The geometry shader is in most cases omitted except when the display style is HdMeshGeomStyleEdgeOnSurf, in which case a geometry shader is required to render edges of output triangles.
The changes include new tessellation evaluation shaders, and an alternative DisplacementTerminal protocol in order to evaluate displacements correctly in a tessellation shader. Some changes also in codegen to include required supporting code such as interstage elements. Also included here is a TfDebug variable for listing shader keys.
Performance tests indicate approximately 40% speedup on average when rendering this type of geometry on a high-end laptop with an NVidia RTX A3000 GPU.
Link to proposal (if applicable)
Fixes Issue(s)
Checklist
I have created this PR based on the dev branch
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