The render delegate currently supports the following features:

• RPrim Support
  • Mesh
    • All primvars are supported, st/uv is accessible through the built-in uv attribute on the mesh
    • Normal primvars are translated to Arnold built-in attributes
    • Support for the displayColor primvar
    • Subdivision settings
  • Volume
  • Points
• SPrim Support
  • Materials
    • Arnold shaders are supported, the info:id attribute is used to determine the shader type
    • UsdPreviewSurface is translated to Arnold shaders
    • UsdTransform nodes
    • Per-face material assignments
  • Lights
    • Distant Light
    • Sphere Light
    • Disk Light
    • Rect Light
    • Cylinder Light
    • Dome Light
    • Shaping Parameters
  • Light and Shading Linking
  • ExtComputation
  • HdCamera
    • Perspective projection
• BPrim Support
  • Render Buffer
  • OpenVDB Asset
• Point Instancer, including nesting of Point Instancers and instancing Volumes
• Selection in USD View and other applications using the primId AOV
• Displaying the Color, Depth, and PrimID AOVs
• Motion Blur
  • Deformation
  • Transformation
• Rendervar support
  • Raw Rendervars
  • Primvar Rendervars
  • LPE Rendervars
  • SourceName parameter
  • DataType parameter
  • Setting up Arnold filters via "arnold:filter_type"
    • Filtering parameters via "arnold:param_name"
    • Filtering parameters via "arnold:filter_node_entry:param_name"
• USD Skel support
• HdExtComputation support for poly meshes
• 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
• Basis Curves support
  • Remapping uv/st to uvs
  • Remapping normals to orientations
• Pause and Resume API
• Half and Double types
• USDZ texture support. For usdz files, tx files are saved in a folder named .usdz_tx.

Limitations

• Crash on Linux at startup with usdview : Currently, the Arnold library needs to be ld-preloaded to avoid the crash, e.g. LD_PRELOAD=/path_to_arnold/bin/ [libai.so](http://libai.so) usdview scene.usda
• Ignoring primvars:arnold:basis on curves
• No support for periodic or pinned curves
• 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 coordsys support
• No support for orthographic cameras

Node Registry Plugin

The Node Registry plugin supports the current features:

• Registering Sdr nodes for every built-in shader and custom shader
  • Setting up the asset URI either to <built-in> or to the path of the shader library providing the shader.
  • Creating all parameters.

Limitations

• No nodes registered for
  • Shapes
  • Lights
  • Filters
  • Drivers
• No node is registered for the options node
• Metadata is not converted for any node

Arnold USD Procedural

The Arnold procedural supports the vast majority of USD shapes:

• USD Geom primitives
  • UsdGeomMesh
  • UsdGeomCurves
  • UsdGeomBasisCurves
  • UsdGeomPoints
  • UsdGeomCube
  • UsdGeomSphere
  • UsdGeomCone
  • UsdGeomCylinder
  • UsdPointInstancer
  • UsdVolume
  • UsdGeomCamera
  • primvars are translated as user data
• USD Lux primitives
  • UsdLuxDistantLight
  • UsdLuxDomeLight
  • UsdLuxDiskLight
  • UsdLuxSphereLight
  • UsdLuxRectLight
  • UsdLuxGeometryLight
  • Support for textured lights (dome, rectangle, and geometry)
• USD native shaders
  • UsdPreviewSurface
  • UsdPrimVar
  • UsdUVTexture
  • Per-channel connections via adapter nodes
  • UsdTransform nodes
• UsdSkel support
• Arnold shaders supported as UsdShade nodes (where info:id gives the shader type)
• Support for any additional Arnold parameter in USD nodes (e.g. attribute primvars:arnold:subdiv_iterations in a UsdGeomMesh)
• Support for any Arnold node type (e.g. USD type ArnoldSetParameter gets rendered as Arnold set_parameter node)
• Support for multi-threaded parsing of a USD file
• UsdRender schema support
• Half and Double types
• Usd Purpose

Limitations

Currently unsupported:

• Nurbs