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USD-Arnold

USD Schemas and tools for exchanging Arnold shader information between multiple 3rd party packages.

Project Goals

• Have a centralized set of schemas describing Arnold materials.
• Provide writers and readers for rendering applications for seamlessly transferring shader information from one application to another.

Modules

Current

• usdAi schema.
  • AiNodeApi - Handling generic Arnold nodes.
  • AiShapeAPI - Handling Arnold shape options, like visibility, sidedness, self-shadows, and receive-shadows.
  • AiMaterialAPI - Defining Arnold shader relationships.
  • AiProcedural - Schema for Arnold's procedural node.
  • AiVolume - Schema for Arnold's volume node.
• Shader exporter for usdMaya. A custom shading mode exporter for Maya that exports all Arnold shader definitions via MtoA. We support MtoA-1.2 and MtoA-1.4.
• Tools for usdKatana. Ops for describing and reading in procedurals to Katana.
• Arnold render delegate.
• Arnold shader discovery and parsing.

Planned

• Adding a material importer for usdKatana. For more information, see building USD.
• Making sure USD-Arnold works with a base installation of USD.
• Build all the packages at once.
• Add windows support.

Building

Our build process is designed to build USD-Arnold as multiple rez packages, so the different components need to be built separately from the main schema.

At this moment USD-Arnold relies on several customizations and fixes to USD, most of which have their PR and waiting to be merged back.

Use our custom build of USD

Building Luma Pictures' flavor of USD is the easiest option, we provide a set of new features, mostly to usdMaya and usdKatana, none of which are breaking any existing behavior in USD. Clone the repository at https://github.com/LumaPictures/USD and build the branch tg/luma/luma following the official build instructions. Note, we changed the default implementation for TfHashMap and TfHashSet to improve stability, make sure you build all your plugins using this version.

Use the official version and apply patches

Clone the latest dev version of USD, and apply the following change to support importing arnold materials in Katana:

Replace the file with Luma's version.

Build enviroment

Requirements

We use and test with the following library versions.

You can use configuration variables to enable/disable individual components during the build process. These are the following.

• BUILD_USD_PLUGIN - Generating the schemas.
• BUILD_USD_IMAGING_PLUGIN - Building the render delegate and ndr plugins.
• BUILD_USD_MAYA_PLUGIN - Building the usdMaya plugin.
• BUILD_USD_KATANA_PLUGIN - Building the usdKatana plugin.

TODO: Finish.

Contributing

TODO.