Autodesk: Skip use of geometry shader for patch tessellation when possible

[erikaharrison-adsk]

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)

• N/A

Fixes Issue(s)

• N/A

Checklist

• I have created this PR based on the dev branch

• I have followed the coding conventions

• I have added unit tests that exercise this functionality (Reference:
  testing guidelines)

• I have verified that all unit tests pass with the proposed changes

• I have submitted a signed Contributor License Agreement (Reference:
  Contributor License Agreement instructions)

[jesschimein]

Filed as internal issue #USD-10438

[jesschimein]

/AzurePipelines run

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[tcauchois]

Exciting!

[davidgyu]

I don't think the TfDebug code introduced here is needed.

It matches existing functionality provided by TF_DEBUG=HDST_DUMP_GLSLFX_CONFIG

[erikaharrison-adsk]

@davidgyu PR has been updated based on this feedback.

[jesschimein]

/AzurePipelines run

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