Alembic primvars with "varying" in the name don't work in Solaris

[arnold-support]

Describe the bug If you export a shape with varying user data to alembic, and the parameter is named something like "mtoa_varying_Pref" or "test_varying_Pref", then in Solaris that primvar does not work.

To Reproduce Steps to reproduce the behavior:

1. Extract arnold-abc-test.zip. It has an abc exported from Maya with Arnold > Scene Export > Export Selected to Alembic. In Maya, the shape has varying user data named "test_varying_Pref" (it was named "mtoa_varying_Pref" but I changed it to "test").
2. In Solaris, use the Sublayer LOP to bring in the abc file
3. Assign a material that uses a user data shader to access "test_varying_Pref"
4. Render. You get the default color from the user data shader.

With "mtoa_varying_Pref" as the attribute name, here's the ultimate differences in usda. Arnold Alembic export:

        custom point3d[] primvars:Pref (
            interpolation = "varying"
        )
        point3d[] primvars:Pref.timeSamples = {
            0: [(0.14877812564373016, -0.9876883625984192
        }

Maya Alembic export:

        custom point3d[] primvars:mtoa_varying_Pref
        point3d[] primvars:mtoa_varying_Pref.timeSamples = {
            0: [(0.14877812564373016, -0.9876883625984192, -0.
        }

Expected behavior A clear and concise description of what you expected to happen.

Screenshots If applicable, add screenshots to help explain your problem.

Used Software Versions

• Latest Arnold available to me on 15 March 2023

[autodesk-oss-arnold-bot[bot]]

Issue synced internally to ARNOLD-13337