tinyusdz/tests/feat/mtlx

MaterialX Export Feature Tests

This directory contains tests for the MaterialX XML export functionality in TinyUSDZ.

Overview

The MaterialX export feature allows converting TinyUSDZ materials (particularly OpenPBR Surface Shader) to MaterialX 1.38 XML format, which is compatible with Three.js WebGPU renderer and other MaterialX-compliant renderers.

Building and Running Tests

Prerequisites

1. Build the main TinyUSDZ library first:

   cd ../../../
   mkdir -p build && cd build
   cmake ..
   make
   

Build the Test

From this directory:

make

Run the Test

make run

This will:

• Create a RenderMaterial with OpenPBR shader properties
• Export it to MaterialX XML format
• Save the output to example_openpbr_material.mtlx
• Display the generated XML

Clean Build Artifacts

make clean

View Help

make help

Test Files

• threejs_mtlx_export_example.cc - Demonstrates MaterialX export API usage
• Makefile - Standalone build configuration
• README.md - This file

Expected Output

The test creates a MaterialX 1.38 XML document with:

• <open_pbr_surface> shader node with all OpenPBR parameters
• <surfacematerial> that references the shader
• Proper type declarations (float, color3, vector3)

Example material properties tested:

• Base layer (metallic gold-like material)
• Specular reflections
• Clear coat layer
• Emission settings
• Geometry modifiers (normal, tangent, opacity)

Integration

This export functionality is part of the Three.js material exporter in:

• src/tydra/threejs-exporter.hh
• src/tydra/threejs-exporter.cc

The API is simple:

ThreeJSMaterialExporter exporter;
std::string mtlx_output;
bool success = exporter.ExportMaterialX(material, mtlx_output);

MaterialX Schema Support

Currently supports:

• ✅ OpenPBR Surface Shader → <open_pbr_surface> (MaterialX 1.38)
• ✅ UsdPreviewSurface → <standard_surface> (fallback)
• ✅ All 35+ OpenPBR parameters
• ✅ Texture node references
• ✅ Constant value exports

Further Reading

• MaterialX Specification
• OpenPBR Surface Documentation
• Three.js MaterialX Support