Jonathan Mack

karma can only render triangles, It's probably just convexing it differently than the opengl viewer, which also can only draw triangles. If you explicitly convert to triangles before rendering, you can control how the shape is convexed.

I think quality in ffmpeg is a 2 digit number, so 100 would be truncated to 10 and produce a very low quality video. Try setting the quality to 10 and see if it produces an identical file.

Tim Crowson
Attached image:
- green is the diffuse color of the mtlx shader
- blue is the Usd Preview Surface color
- Houdini GL ignores the latter and renders the former (but this seemed to work as expect in 20.0

Basically... I can't seem to author a custom UsdPreviewSurface in 20.5 and actually see it in GL.

no, you cannot. The viewer will use the 'best' shader it knows how to render. Since the HoudiniGL viewer knows how to render a mtlx shader, it will use that.