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<!-- SPDX-License-Identifier: Apache-2.0 -->Arnold USD
This repository contains a set of components and tools to use the Arnold renderer with Pixar's Universal Scene Description. Notably, the following components are included:
- Hydra render delegate
- Arnold procedural for USD
- Schemas to describe an Arnold scene in USD
Contributions are welcome! Please make sure to read the contribution guidelines.
Building and installation
Please follow the building instructions. To use the components, provided you installed in <arnold-usd_dir>
, set the following environment variables:
- Add
<arnold-usd_dir>/procedural
toARNOLD_PLUGIN_PATH
for the Arnoldusd
procedural. - Add
<arnold-usd_dir>/lib/python
toPYTHONPATH
for the Python schema bindings. - Add
<arnold-usd_dir>/plugin
toPXR_PLUGINPATH_NAME
for the Hydra render delegate and the Node Registry plugin. - Add
<arnold-usd_dir>/lib/usd
toPXR_PLUGINPATH_NAME
for the USD schemas. - Add
<arnold-usd_dir>/lib
toLD_LIBRARY_PATH
on Linux,PATH
on Windows andDYLD_LIBRARY_PATH
on Mac.
Hydra Render Delegate
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
- Mesh
- 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
- Arnold shaders are supported, the
- Lights
- Distant Light
- Sphere Light
- Disk Light
- Rect Light
- Cylinder Light
- Dome Light
- Shaping Parameters
- Light and Shadow Linking
- ExtComputation
- HdCamera
- Perspective projection
- Materials
- 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
- Using motion vectors on Points
- 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 polymeshes
- 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
- Deep render products
- Basis Curves support
- Remapping uv/st to uvs
- Remapping normals to orientations
- Pause and Resume API
- Half and Double types
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 usdview scene.usda
- Ignoring primvars:arnold:basis on curves
- No support for periodic or pinned curves
- No field3d volume grids
- 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
- Can't open textures from usdz files
- No support for orthographic cameras
- Face-varying primvars are not correctly interpolated
- Possible flicker when using cryptomatte: this is due to the prototypes not being named in a deterministic way. Setting the environment variable
USD_ASSIGN_PROTOTYPES_DETERMINISTICALLY
should fix this issue.
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.
- Setting up the asset URI either to
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 procedural supports the following features:
- 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
- Light Linking
- Multiple frames in a single file
Limitations Currently unsupported:
- Nurbs
Arnold USD Procedural
The scene delegate supports the following features:
- Arnold built-in shapes
- Render time procedurals shipped with the core
Limitations Currently unsupported:
- Custom procedurals
- Lights
- Displaying Arnold schemas with non-Arnold render delegates
Testsuite
Running the arnold-usd testsuite requires the latest version of Arnold, that can be downloaded at https://www.arnoldrenderer.com/arnold/download/ It is not supported for older versions of Arnold.
Acknowledgments
- Luma Pictures' usd-arnold
- RodeoFX's OpenWalter
- Ben Asher
- Sebastien Blaineau-Ortega
- Chad Dombrova
- Guillaume Laforge
- Julian Hodgson
- Thiago Ize
- Pal Mezei
- Paul Molodowitch
- Nathan Rusch
- Frederic Servant
- Charles Flèche
- Raymond Kreppene
- Julien Deboise
- Jerry Gamache
- Tom Minor
- Cyril Pichard