USD For Unity

Overview

USD (Universal Scene Description) is a file format that can store time-sampled 3D scene. It is something like 'Better Alembic' or 'Better FBX' developed by Disney / Pixar.
This plugin allow you to import USD or Alembic scene to Unity and export Unity scene to USD or Alembic file. The above image is exported scene of Candy Rock Star in usdview.

Requirements

• Supported platform is Windows (64 bit), Mac (64 bit) and Linux (64 bit).
• On Windows, VS2015 runtime must be installed (usually installed on recent version of Windows).
• Tested on Unity 5.4, 5.5, 5.6 and likely works on other 5.x versions.

Usage

• Import this package: USDForUnity.unitypackage
• On Linux, you need to build the plugin from source
• Assets -> "Import USD or Alembic" and select file

Some of USD's features are supported, some of others are not.

• Xform, Camera and Mesh schemas are supported. Mesh topology can be dynamic.
• Animation can be interpolated, which was not supported by AlembicImporter.
• Normals and tangents can be generated on the fly. But generating tangent is very very slow and not recommended to do it at runtime.
• You can precompute normals and tangents via "Precompute normals / tangents" button. It precomputes normals (+ tangents) and store them into USD file.
• Variant is supported. You can switch variant sets and variants via inspector.
• Reference & instance is supported. Mesh data is shared among instances that have same master.
• Payload is supported. All payloads will be loaded when the scene is loaded.
• Subdivision is not supported. It is planned but unlikely to come soon.
• NURBS is not supported.
• Point instancer is not supported yet.

Notes

• This plugin is designed to stream data directory from USD (or Alembic) files because storing all vertex cache data in memory is sometimes impractical. For this reason, USD files must be in StreamingAssets directory at runtime. We are planning to add converter instead of direct USD file streaming for better performance and runtime portability (just like built-in FBX importer is doing).

• This plugin doesn't care about materials as USD itself doesn't support material schema. I heard USD will support material schema that can store basic PBR parameters. When it is done, this plugin will adapt to it. Apart from that, we are planning to add NVIDIA's MDL support as we have clients who are using it.

• This plugin supports import & export skinning animation (bone + vertex weight). But these data are stored in custom attributes and unlikely to compatible with other tools for now. I heard USD's mesh schema will support bone + weight attributes. When it is done, this plugin will adapt to it.
  Custom attributes in Mesh schema that this plugin uses:

    int maxBoneWeights
    int[] boneIndices
    float[] boneWeights
    matrix4d[] bindposes
    token rootBone
    token[] bones
    float2[] primvars:uv
    float4[] tangents

• You can build this plugin from source.
• Windows: Just open Plugin/usdi.sln with VisualStudio2015 and build. Pre-built USD libraries are included in this repository (It is based on our fork that includes some bug fixes and optimizations for Windows).
• non-Windows: There is cmake build file (Plugin/CMakeLists.txt). In this case you must build USD by yourself, but building this plugin is straightforward as required libraries are almost same as USD. I confirmed it works on Mac and Ubuntu 16 (Unity for Linux is here).

License

MIT