When loading the latest version of the Alab scene (v2), materials don't render correctly. I've narrowed the problem down to the following issues:
- Some of the UV primvars in the Alab scene are of type Float2Array which is unusual. The Blender USD importer expects UV primvars to be of type TexCoord (e.g., TexCoord2fArray). Hence, some of the Alab UV maps are not getting imported, resulting in the wrong UVs getting applied in the Blender scene. The importer logic should be extended to import Float2Array primvars as texture coordinates as well.
- The USD importer is attempting to read the varname input of the UsdPrimvarReader_float2 shader as a TfToken, which conforms to the original UsdPreviewSurface specification. However, in the latest specification, varname is a string. This type mismatch when reading the input can result in an empty map name in the UV Map node in Blender and the wrong texture coordinates getting applies.
- For materials that have an authored opacity value, the importer sets the material Blend Mode to Alpha Blend. In the Alab scene this causes artifacts due to object sorting issues. Setting the Blend Mode to Alpha Hashed provides improved results.
To reproduce the issue, the Alab USD can be downloaded here:
I created branch tmp-usd-alab-v2-T100452 with work in progress on fixes so far.
