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https://github.com/autodesk/arnold-usd

Arnold components for USD
https://github.com/autodesk/arnold-usd

arnold houdini hydra katana maya usd

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Arnold components for USD

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README 

        

Arnold USD

==========



This repository contains a set of components and tools to use the [Arnold](https://www.arnoldrenderer.com) renderer with Pixar's [Universal Scene Description](https://github.com/PixarAnimationStudios/USD). 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](CONTRIBUTING.md).



## Building and installation



Please follow the [building instructions](docs/building.md). To use the components, provided you installed in ``, set the following environment variables:



- Add `/procedural` to `ARNOLD_PLUGIN_PATH` for the Arnold `usd` procedural.

- Add `/lib/python` to `PYTHONPATH` for the Python schema bindings.

- Add `/plugin` to `PXR_PLUGINPATH_NAME` for the Hydra render delegate and the Node Registry plugin.

- Add `/lib/usd` to `PXR_PLUGINPATH_NAME` for the USD schemas.

- Add `/lib` to `LD_LIBRARY_PATH` on Linux, `PATH` on Windows and `DYLD_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

- 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 Shadow 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

    - 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 `` 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 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](https://github.com/LumaPictures/usd-arnold)

- RodeoFX's [OpenWalter](https://github.com/rodeofx/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