USD: Specific file is missing textures.

[mwestphal]

Describe the bug
Loading this file cause an unexpected exception: https://github.com/mwestphal/assets/tree/main/full_assets/StandardShaderBall

Works fine in blender

Warning: in _ReportErrors at line 2885 of /__w/f3d-superbuild/f3d-superbuild/build/superbuild/openusd/src/pxr/usd/usd/stage.cpp -- In </standard_shader_ball_scene/materials/examples/mtlx>: Could not open asset @/home/glow/tmp/assets/full_assets/StandardShaderBall/example_materials/plastic.mtlx@ for reference introduced by @/home/glow/tmp/assets/full_assets/StandardShaderBall/layers/example_materials.usda@</standard_shader_ball_scene/materials/examples/mtlx> -- Cannot determine file format for @/home/glow/tmp/assets/full_assets/StandardShaderBall/example_materials/plastic.mtlx:SDF_FORMAT_ARGS:target=usd@. (instantiating stage on stage @/home/glow/tmp/assets/full_assets/StandardShaderBall/standard_shader_ball_scene.usda@ <0x55d062890640>)
Warning: in _ReportErrors at line 2885 of /__w/f3d-superbuild/f3d-superbuild/build/superbuild/openusd/src/pxr/usd/usd/stage.cpp -- In </standard_shader_ball_scene/materials/examples/mtlx>: Could not open asset @/home/glow/tmp/assets/full_assets/StandardShaderBall/example_materials/gold.mtlx@ for reference introduced by @/home/glow/tmp/assets/full_assets/StandardShaderBall/layers/example_materials.usda@</standard_shader_ball_scene/materials/examples/mtlx> -- Cannot determine file format for @/home/glow/tmp/assets/full_assets/StandardShaderBall/example_materials/gold.mtlx:SDF_FORMAT_ARGS:target=usd@. (instantiating stage on stage @/home/glow/tmp/assets/full_assets/StandardShaderBall/standard_shader_ball_scene.usda@ <0x55d062890640>)
Warning: in _ReportErrors at line 2885 of /__w/f3d-superbuild/f3d-superbuild/build/superbuild/openusd/src/pxr/usd/usd/stage.cpp -- In </standard_shader_ball_scene/materials/examples/mtlx>: Could not open asset @/home/glow/tmp/assets/full_assets/StandardShaderBall/example_materials/glass.mtlx@ for reference introduced by @/home/glow/tmp/assets/full_assets/StandardShaderBall/layers/example_materials.usda@</standard_shader_ball_scene/materials/examples/mtlx> -- Cannot determine file format for @/home/glow/tmp/assets/full_assets/StandardShaderBall/example_materials/glass.mtlx:SDF_FORMAT_ARGS:target=usd@. (instantiating stage on stage @/home/glow/tmp/assets/full_assets/StandardShaderBall/standard_shader_ball_scene.usda@ <0x55d062890640>)
Warning: in _ReportErrors at line 2885 of /__w/f3d-superbuild/f3d-superbuild/build/superbuild/openusd/src/pxr/usd/usd/stage.cpp -- In </standard_shader_ball_scene/materials/examples/mtlx>: Could not open asset @/home/glow/tmp/assets/full_assets/StandardShaderBall/example_materials/bubblegum.mtlx@ for reference introduced by @/home/glow/tmp/assets/full_assets/StandardShaderBall/layers/example_materials.usda@</standard_shader_ball_scene/materials/examples/mtlx> -- Cannot determine file format for @/home/glow/tmp/assets/full_assets/StandardShaderBall/example_materials/bubblegum.mtlx:SDF_FORMAT_ARGS:target=usd@. (instantiating stage on stage @/home/glow/tmp/assets/full_assets/StandardShaderBall/standard_shader_ball_scene.usda@ <0x55d062890640>)
F3D encountered an unexpected exception:
Used null prim

[Meakk]

Managed to fix the problem but there's now a new issue unrelated to USD: we cannot read EXR files from memory.
I'll open another issue.

[Meakk]

#1187

[mwestphal]

Confirmed now working without texture.

[mwestphal]

closing as the main issue is fixed