hdMtlx: _GetMxNodeType should use the MaterialX library to find the node type.

[JGamache-autodesk]

Description of Issue

• Local surface shaders (like a Lambert-like PBR surface for Maya export) are not recognized even though the definition file was read and the library contains the node definition.

Steps to Reproduce

1. Copy the attached maya_surfaces.mtlx file to the local MaterialX library (I put it in libraries/bxdf of my MaterialX installation since hdSt does not declare an environment variable to define extra library paths to search).
2. Load the attached LambertSphere.usda scene in usdView
3. Warning: Unsupported node type 'ND_MayaLambert_surfaceshader'

I can get a working Lambert by updating _GetMxNodeType to fetch back mxDoc->getNodeDef(hdNodeType.GetString())->getNodeString(). Would that be a correct fix?

LambertSphere.zip

System Information (OS, Hardware)

Package Versions

Build Flags

[jilliene]

Filed as internal issue #USD-6734

[klucknav]

Thank you, initially we were only supporting UsdPreviewSurface and StandardSurface node types, but we have a fix coming.