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PixarAnimationStudios / OpenUSD

Universal Scene Description
http://www.openusd.org
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MaterialX texcoord-related regression in v24.03 #3048

Open pablode opened 3 weeks ago

pablode commented 3 weeks ago

Description of Issue

Following asset looks different after upgrading USD: Buffer_Interleaved_01.zip

v23.08 bug_2308

v24.03 bug_2403

(see comment below for an explanation)

Steps to Reproduce

  1. open the asset in usdview

System Information (OS, Hardware)

Occurs on both Windows (OpenGL) and macOS (Metal)

Package Versions

v24.03 and v24.05 are affected

Build Flags

--openimageio --opencolorio

pablode commented 3 weeks ago

I believe to have found the cause. First, the texture coordinates are faulty:

texCoord2f[] primvars:st0 = [(0, 1), (1, 0), (5.831554e-39, 1), (0, 1), (5.831554e-39, 1), (0, 1)] (
    interpolation = "vertex"
)

However, they are irrelevant because the _BaseColorGrey.png texture that is being sampled is 100% grey and is defined with the periodic address mode in both u and v directions. Hence, regardless of UV values, grey should be returned and not black.

Although on macOS the color is solid black, I have observed flickering of the correct colors with the OpenGL backend. Perhaps this is somehow related to the newly-introduced tangent frame computation?

jesschimein commented 3 weeks ago

Filed as internal issue #USD-9565