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Table of Contents

This page provides information on support for the Universal Scene Description in V-Ray for Maya.

 

Overview

 

USD or Universal Scene Description (.usd)  is a framework and file format , developed by Pixar, that allows 3D scenes and assets to be transferred and edited on multiple applications. USD focuses on workflows that allow multiple users to collaborate on a project without conflict by using non-destructive editing, asset versions and variations. For more information, visit Getting Started with USD.  

 

Workflow

Import

 

USD files can be loaded in Maya and rendered with V-Ray using the MayaUSD plugin with mayaUsdProxy nodes.

We recommend following a standard workflow with MayaUSD when rendering with V-Ray. See the video for more.

For V-Ray 5, update 2 it is recommended to use MayaUSD 0.10.0 or newer.

  • In Maya, go to Create > Universal Scene Description (USD) > Stage From File...
  • Locate the desired USD file in the directory window.
  • Click on Create.

 

 

Importing V-Ray materials using USD files

The standard workflow imports V-Ray materials as Maya materials.

 

 

  • V-Ray materials that are exported as USD files can be imported into Maya as native V-Ray materials using the mayaUSDImport command.
MEL example
mayaUSDImport -file "/path/to/file.usd" -primPath "/" -shadingMode "vray" "none"

 

 

  • Alternatively, there is an interface menu equivalent to the mayaUSDImport command. To import a USD file with native V-Ray materials, go to File > Import. In the pop-up menu, set the File Type to USD Import. Set the Plug-in Configuration to V-Ray.

Click here for UI example

 

 

 

 

 

Importing V-Ray Physical Cameras using USD files

 

USD files can be used to import V-Ray Physical Cameras and all their attributes using the mayaUSDImport command. 

MEL example
mayaUSDImport -file"/path/to/file.usd" -primPath "/"

If you are using a zip-installed V-Ray 5, update 2, for Maya or newer, make sure to set up the PXR_PLUGINPATH_NAME environment variable. Otherwise, exporting and importing V-Ray Physical Cameras is impossible. For more information on setting up environment variables, please visit the Installation from zip page.

 

 

Export

 

  • Exporting V-Ray shaders to USD versions up to 0.13.0 including:
    from File > Export All... or Export Selection... (select the Option box) > General Options and as File Type, select USD Export. Under File Type Specific Options > Geometry, set the Materials to V-Ray MaterialExporter.

    When using USD 0.15.0 or below, if V-Ray is not selected as Plug-In Configuration, but the V-Ray Materials option is enabled, the export fails with an error. If V-Ray is selected as a Plug-In Configuration, but the V-Ray Material option is disabled, the exported USD does not contain the V-Ray materials.

  • For USD version 0.15.0 or higher:
    in the File > Export All Options window, set the File Type to USD Export, choose whether the materials are to be exported as USD Preview Surface or as V-Ray materials. You can export all materials in the scene as one or multiple types of networks.

    • Alternatively, you can use the Export Materials to USD option in the V-Ray menu. For more information, please visit the Export Materials to USD page.

 

 

Click to expand for Export Options screenshots...

 

For USD versions up to 0.13.0

 

For USD version 0.15.0 or later

 

Exporting lights to USD does not require the V-Ray Material Exporter to be selected in the Export to USD menu.


Supported Maya USD Versions

  • 0.8.0 (bundled in Maya 2022)
  • 0.9.0
  • 0.10.0 (bundled in Maya 2022.1)
  • 0.11.0 (bundled in Maya 2022.2)
  • 0.12.0
  • 0.13.0
  • 0.15.0 (bundled in Maya 2022.3)
  • 0.16.0 (bundled in Maya 2023)
  • 0.17.0
  • 0.18.0 (bundled in Maya 2023.1)
  • 0.19.0 (bundled in Maya 2023.2)

Maya USD versions 0.17.0 and newer are supported on Maya 2022 and newer. Running these USD versions on earlier versions of Maya, prints out a warning.

 

 

Supported features

USD Rendering

The following features are supported when rendering USD files with V-Ray for Maya:

  • Static meshes
  • Animated transforming meshes
  • Animated deforming meshes
  • Motion blur for animated meshes
  • Particles
  • Hair
  • VDB volumes referenced in USD files
  • UsdPreviewSurface material
  • V-Ray materials encoded in USD files
  • V-Ray textures encoded in USD files
  • V-Ray lights encoded in USD files.1
  • USD light types encoded in USD files (including Maya's Spot, Direct, Point lights).
  • V-Ray Displacement and Subdivision encoded in USD files
  • Local rendering of USD edits that are not saved to USD file on disc
  • Bifrost USD graphs
  • Animation of shader parameters

  • Maya nParticles and nParticle animations6

  • USD Skel
  • Dynamic USD plugins (e.g. Golaem for USD)
  • VDB shaders

  • Custom V-Ray attributes with USD Utility Textures such as VRayUserScalar and VRayUserColor.

 

 

Rendering a scene with USD edits that are not saved to a USD file on disc will likely produce an unexpected result when using Distributed Rendering, or submitting to the Chaos Cloud, or exporting to .vrscene from Maya.

Make sure your USD edits are always saved when using these features. USD edits will generally render correctly only when rendering locally.

Assets linked in USD files may fail to resolve when using Distributed Rendering, or submitting to the Chaos Cloud, or exporting to .vrscene from Maya.

For example, if a Maya scene loads a USD file that in turn loads textures and / or other USD files.

USD Export

The following features are supported when exporting USD files from Maya with V-Ray:

  • V-Ray shaders (materials and textures). For USD version up to 0.13 the required exporter is V-Ray Material Exporter. For version 0.15 and above, the V-Ray Plug-in Configuration needs to be selected.2
  • V-Ray lights1
  • V-Ray Displacement; V-Ray Subdivision
  • V-Ray Physical Camera
  • Maya nParticles and nParticle animations6

  • Custom V-Ray attributes with USD Utility Textures such as VRayUserScalar and VRayUserColor.

  • Render elements9

 

Exporting V-Ray materials and VRayDisplacement

Materials, including V-Ray materials, can be exported to USD by using Maya's File > Export / Export Selected menu.

To export V-Ray materials to USD files without including geometry, the vrayExportUsdMaterials command can be used.

MEL example
vrayExportUsdMaterials "<path/to/usdFile.usd*>"

The example above exports all materials in the scene to a USD file. This includes V-Ray materials and Maya materials supported by V-Ray like Lambert, Blinn and usdPreviewSurface.

The vrayExportUsdMaterials command offers some additional optional flags that can be used to export VRayDisplacement and to only export the current selection:

-selection - When specified, only the selected materials are exported. Selecting a mesh will export the assigned material and its shading network, without the actual mesh. The flag is used without arguments.

-displacement - Enables export of VRayDisplacement and VRaySubdivision. The flag is used without arguments.

-help – Prints out a help message in cases where there is an error with the command.

 

Notes:

  • The optional flags can be combined.
  • The usd extension used in the file path string argument specify whether a binary .usd file or an ASCII .usda will be exported.
  • If the command has an invalid or incorrectly used flag, a corresponding error message is printed. For a more detailed message add a -help flag to the command.
  • Upon successful export, a message is printed.

 

MEL: Example usage
// Exports all scene materials.
vrayExportUsdMaterials "<path/to/usdFile.usd*>";
 
// Exports the currently selected material(s). For selected meshes, only their assigned materials are exported, without the actual mesh.
vrayExportUsdMaterials -selection "<path/to/usdFile.usd*>;

// Exports all scene materials, including VRayDisplcament and VRaySubdivision.
vrayExportUsdMaterials -displacement "<path/to/usdFile.usd*>;

// Exports the currently selected material(s), including VRayDisplacement and VRaySubdivision.
vrayExportUsdMaterials -selection -displacement "<path/to/usdFile.usd*>;

The order of flags and arguments is not strict. The flags can be placed before and/or after the string argument for the export file path.

Temporary Limitations

The following features are still in development and support for them will be added soon.

  1. Lights are supported with USD version 0.10.0 or newer.
  2. Exporting light textures are supported only with the "Export All" option
  3. Exporting V-Ray Fur to USD from Maya
  4. Detecting USD edits in IPR
  5. Importing V-Ray materials applied to particle animations from USD files
  6. nParticles and nParticle animations are supported with USD version 0.16.0. nParticle animations with an emitter are not visible in the viewport
  7. Exporting volumes to USD files
  8. Exporting a USD scene with Hair
  9. Some Render Elements are not supported for USD export. V-Ray prints out a warning when an unsupported render element is submitted for export.