Arnold USD Toolset

Arnold USD is a toolset for Universal Scene Description . The project contains several tools:

• Arnold Procedural
• Arnold to USD converter command line executable
• Hydra Render Delegate
• Set of USD schemas to describe an Arnold scene using USD

Building and Dependencies

Building

Contributing to the Project

Contributing

Setting up environment

After compiling and installing the project

• Add <prefix>/bin to PATH for the Arnold to USD writer executable.
• Add <prefix>/lib/python to PYTHONPATH for the python schema bindings.
• Add <prefix>/plugin to PXR_PLUGINPATH_NAME for the Hydra Render Delegate.
• Add <prefix>/lib/usd to the PXR_PLUGINPATH_NAME for the USD Schemas.
• Add <prefix>/lib to LD_LIBRARY_PATH on Linux, PATH on Windows and DYLD_LIBRARY_PATH on Mac.

Features and Limitations

Procedural

Features

• USD shapes : UsdGeomMesh, UsdGeomCurves, UsdGeomPoints, UsdGeomCube, UsdGeomSphere, UsdGeomCone, UsdGeomCylinder. Support for primvars (user data)
• USD Lights : UsdLuxDistantLight, UsdLuxDomeLight, UsdLuxDiskLight, UsdLuxSphereLight, UsdLuxRectLight, UsdLuxGeometryLight.Support for textured lights (dome and rectangle).
• USD native shaders : UsdPreviewSurface, UsdPrimVar*, UsdUVTexture
• Arnold shaders supported as UsdShade nodes (where info:id gives the shader type)
• Support for any additional arnold parameter in USD nodes (ex: attribute arnold:subdiv_iterations in a UsdGeomMesh)
• Support for any arnold node type (ex: Usd type ArnoldSetParameter gets rendered as arnold set_parameter node)
• Support for multi-threaded parsing of a USD file

Limitations

• Nurbs
• Point Instancer
• Cameras

Render Delegate

Features

• RPrim Support
  • Mesh
    • All primvars are supported, st/uv is accessible through the built-in uv attribute on the mesh
    • Support for the displayColor primvar
    • Subdivision settings
  • Volume
• SPrim Support
  • Material
    • Pixar Preview surfaces are translated to arnold nodes, otherwise the info:id attribute is used to determine the shader type
  • Distant Light
  • Sphere Light
  • Disk Light
  • Rect Light
  • Cylinder Light
  • Dome Light
• BPrim Support
  • Render Buffer
  • OpenVDB Asset
• Point Instancer
  • Including nesting of Point Instancers
• Selection in USD View and other applications using the primId aov
• Displaying the Color, Depth and PrimID AOVs
• Motion Blur
  • Deformation
  • Transformation
• Render Settings via the Render Delegate
  • Sampling parameters
  • Threading parameters
  • Ignore parameters
  • Profiling and logging parameters
  • Switching between CPU and GPU mode seamlessly
  • Default values are configurable through environment variables for most of these parameters

Limitations

• No motion blur support for the Point Instancer attributes
• Can’t preview arbitrary primvar AOVs
• No basisCurves
• No field3d volume grids
  • Not all the parameters are accessible through the render settings
  • Texture Cache size
• Texture generation parameters (automip, autotile)
• No normal maps on the UsdPreviewSurface
• Only converging renders are supported (ie. it’s not possible to block the viewport until the render finishes)
• No HdExtComputation and UsdSkel computation via the render delegate
• No of physical camera parameters
• No points
• No coordsys support

Acknowledgments

In alphabetical order:

• Ben Asher
• Chad Dombrova
• Nathan Rusch
• Paul Molodowitch