This README visualizes a subset of the graphical tests and serves as an artifact for discussion around
- the conformance of guc and the MaterialX glTF PBR implementation
- UsdPreviewSurface limitations and shading differences
- existing problems in guc and involved technologies.
Note: please see run_tests.sh for additional notes and deactivated tests.
glTF-Asset-Generator (source)
| Index | USD+UsdPreviewSurface | USD+MaterialX | glTF Ref. |
|---|---|---|---|
| Accessor_Sparse | |||
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| Accessor_SparseType | |||
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| Buffer_Interleaved | |||
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| Instancing | |||
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| Material | |||
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| Material_AlphaBlend | |||
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| Material_AlphaMask | |||
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| Material_DoubleSided | |||
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| Material_MetallicRoughness | |||
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| Mesh_PrimitiveAttribute | |||
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| Mesh_PrimitiveMode | |||
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| Mesh_PrimitiveVertexColor | |||
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| Mesh_Primitives | |||
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| Mesh_PrimitivesUV | |||
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| Node_Attribute | |||
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| Node_NegativeScale | |||
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| Texture_Sampler | |||
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glTF-Sample-Models (source)
Complex Models
| Name | USD+UsdPreviewSurface | USD+MaterialX |
|---|---|---|
| 2CylinderEngine |  |
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| ABeautifulGame |  |
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| DamagedHelmet |  |
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| IridescenceLamp |  |
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| IridescentDishWithOlives |  |
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| MosquitoInAmber |  |
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| SheenCloth |  |
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| StainedGlassLamp |  |
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| ToyCar |  |
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Feature Tests
| Name | USD+UsdPreviewSurface | USD+MaterialX |
|---|---|---|
| AlphaBlendModeTest |  |
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| AttenuationTest |  |
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| ClearCoatTest |  |
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| EmissiveStrengthTest |  |
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| EnvironmentTest |  |
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| IridescenceDielectricSpheres |  |
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| IridescenceMetallicSpheres |  |
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| LightsPunctualLamp |  |
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| MetalRoughSpheres |  |
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| MetalRoughSpheresNoTextures |  |
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| MultiUVTest |  |
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| NormalTangentMirrorTest |  |
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| NormalTangentTest |  |
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| OrientationTest |  |
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| SpecularTest |  |
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| TextureCoordinateTest |  |
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| TextureEncodingTest |  |
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| TextureSettingsTest |  |
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| TextureTransformTest |  |
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| TextureTransformMultiTest |  |
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| TransmissionRoughnessTest |  |
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| TransmissionTest |  |
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| UnlitTest |  |
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| VertexColorTest |  |
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| Name | USD+UsdPreviewSurface | USD+MaterialX |
|---|---|---|
| Camera_01 |  |
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| CoffeeCart_01 |  |
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| Fangyi |  |
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| Loewe_von_Asparn |  |
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| Perseverance |  |
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| Space_Shuttle |  |
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| MaterialVariants | ||
|---|---|---|
| Variant | UsdPreviewSurface | MaterialX |
| Midnight (0, default) |  |
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| Beach (1) |  |
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Minor observations:
- Brightness differences
Between the UsdPreviewSurface and glTF PBR shading models, the specular response is most likely the cause (see MetalRoughSpheresNoTextures). - Missing transmission color attenuation
For instance, in the TransmissionTest sample model. This seems to be a current limitation of HdStorm's MaterialX integration. - TextureSettingsTest seems to fail
It's actually working, but backface culling is disabled by default. - Environment map artifacts
These were introduced with USD v25.05 and are logged here.
Failures:
- Material_04 looks more specular than it should
This hints at an actual issue in either 1) guc's handling of normal maps, 2) the MaterialX glTF PBR implementation, 3) MaterialXGenGlsl or 4) HdStorm. - ToyCar model cloth is too bright and has shading artifacts
The artifacts exist in MaterialXView too, suggesting an issue with the GLSL sheen implementation, or the MaterialX glTF PBR. - Storm handles greyscale images incorrectly
This can f.i. be seen in TextureLinearInterpolationTest. Logged as MaterialX issue #2257.