tinyusdz/models/OPENPBR_TESTS_README.md

OpenPBR MaterialX Test Files

This directory contains synthetic USDA test files demonstrating OpenPBR materials with textures.

Test Files

Basic Material Tests

1. openpbr-brick-sphere.usda - Simple diffuse material with brick texture

   • OpenPBRSurface with base_color from texture
   • Low metalness (0.0), medium roughness (0.7)
   • Uses: textures/brick.bmp

2. openpbr-metallic-cube.usda - Metallic material with checkerboard texture

   • High metalness (0.8), low roughness (0.2)
   • Specular IOR: 1.5
   • Uses: textures/checkerboard.png

3. openpbr-emissive-plane.usda - Emissive material with cat texture

   • Emission from texture (emission_luminance: 10.0)
   • Low base weight (0.5)
   • Uses: textures/texture-cat.jpg
   • Note: Uses explicit Mesh - material detectable by Tydra

4. openpbr-glass-sphere.usda - Glass/transmission material

   • Zero base weight, full transmission (0.95)
   • Zero roughness for clear glass
   • Transmission color: slight blue tint

5. openpbr-subsurface-sphere.usda - Subsurface scattering material

   • Base color and subsurface color from texture
   • Subsurface weight: 0.5, radius: 0.1
   • Radius scale: (1.0, 0.5, 0.3) for realistic SSS
   • Uses: textures/01.jpg

6. openpbr-coated-cube.usda - Clear coat material

   • Brick texture base with clear coat layer
   • Coat weight: 0.8, coat roughness: 0.1
   • Coat IOR: 1.5
   • Uses: textures/brick.bmp

Multi-Object Scene

7. openpbr-multi-object.usda - Scene with multiple objects and materials
   • BrickSphere: Rough brick material
   • MetalCube: Smooth gold-colored metal (no texture)
   • GlassSphere: Clear glass with transmission
   • GroundPlane: Checkerboard pattern (5x tiled)
   • Note: Only GroundPlane material (CheckerMaterial) is detectable by Tydra as it's an explicit Mesh

Texture Files

All test files reference textures in the textures/ subdirectory:

• brick.bmp - 64x64 red brick pattern with gray mortar (generated)
• checkerboard.png - Black and white checkerboard pattern
• texture-cat.jpg - Cat photo texture
• 01.jpg - Color texture for subsurface scattering

Material Structure

All materials follow this structure:

def Scope "_materials"
{
    def Material "MaterialName"
    {
        token outputs:surface.connect = <path/to/OpenPBRSurface.outputs:surface>

        def Shader "OpenPBRSurface"
        {
            uniform token info:id = "OpenPBRSurface"
            // OpenPBR parameters (inputs:base_color, etc.)
            token outputs:surface
        }

        def Shader "TextureName" (optional)
        {
            uniform token info:id = "UsdUVTexture"
            asset inputs:file = @./textures/filename@
            float2 inputs:texcoord.connect = <path/to/Primvar.outputs:result>
            color3f outputs:rgb
        }

        def Shader "Primvar" (optional)
        {
            uniform token info:id = "UsdPrimvarReader_float2"
            int inputs:index = 0
            float2 outputs:result
        }
    }
}

Shader Node IDs

• OpenPBRSurface: OpenPBR surface shader (info:id = "OpenPBRSurface")
• UsdUVTexture: Texture sampler (info:id = "UsdUVTexture")
• UsdPrimvarReader_float2: UV coordinate reader (info:id = "UsdPrimvarReader_float2")

Note: MaterialX node definition IDs (e.g., "ND_open_pbr_surface_surfaceshader") are not currently supported. Use the simplified USD shader IDs above.

Tydra RenderScene Conversion Notes

The Tydra render converter currently only detects materials bound to explicit Mesh primitives. Parametric primitives (Sphere, Cube) are not converted, so their materials won't appear in RenderScene.

Files with detectable materials:

• openpbr-emissive-plane.usda (uses Mesh)
• openpbr-multi-object.usda (only GroundPlane/CheckerMaterial detected)

Files with non-detectable materials (parametric primitives):

• openpbr-brick-sphere.usda
• openpbr-metallic-cube.usda
• openpbr-glass-sphere.usda
• openpbr-subsurface-sphere.usda
• openpbr-coated-cube.usda

These files still parse correctly and can be used for testing MaterialX parsing, but won't export materials via the WASM MaterialX dumper CLI.

Testing

Native Build

# Parse test
./build/tusdcat models/openpbr-brick-sphere.usda

# Note: OpenPBRSurface may show as "[???] Invalid ShaderNode" in output
# This is a pprinter limitation, not a parsing error

WASM MaterialX Export

cd web/js
npm run dump-materialx -- ../../models/openpbr-emissive-plane.usda -v
npm run dump-materialx -- ../../models/openpbr-multi-object.usda -f json

OpenPBR Parameters Demonstrated

• Base Layer: base_weight, base_color, base_metalness, base_roughness
• Specular: specular_weight, specular_roughness, specular_ior
• Transmission: transmission_color, transmission_weight
• Emission: emission_color, emission_luminance
• Subsurface: subsurface_color, subsurface_weight, subsurface_radius, subsurface_radius_scale
• Coat: coat_weight, coat_roughness, coat_ior, coat_color
• Geometry: geometry_thin_walled (for glass)

Related Files

• create_brick_texture.py - Python script to generate brick.bmp texture
• polysphere-materialx-001.usda - More complex MaterialX scene from Blender