Incorrect drawing if prim is partially transparent / semi transparent

[csyshing]

Describe the bug A clear and concise description of what the bug is.

Hi, We found a drawing issue in VP2 render delegate mode if the prim has some of the faces transparent, attached USD file (partially_transparent_prim.usda) is the super simplified version of one of our production assets.

The geometry's first face (index 0) has been rotated to x+ and has the opacity value set to 0; the inner faces are in red color and the outer faces are in blue color.

When viewing in usdview, the result is displaying as expected:

but in mayaUsd-0.9.0, the result is inccorect:

Steps to reproduce Steps to reproduce the behavior:

1. Launch Maya and load the attached USD file;
2. Rotate and see the result

Expected behavior Expect to match usdview / have the prim drawing correctly.

Attachments partially_transparent_prim.zip

Specs (if applicable):

• OS & version Centos 7.4
• Compiler & version gcc 6.3.1
• Maya version Maya 2020
• Maya USD official 0.9.0 release
• Pixar USD official USD-20.11 release