OpenUSD
OpenUSD, short for Open Universal Scene Description (originally Universal Scene Description or USD), is an open-source framework for describing, composing, simulating, and interchanging 3D scenes and assets between software tools.[1] It was developed internally at Pixar over many years for its film pipeline and released as open-source software on July 26, 2016.[2] Rather than a single file format, USD is a scene graph and a composition engine: it lets large teams assemble complex scenes non-destructively from many layered contributions, which has made it a common authoring and interchange "pipeline" format for visual effects, animation, design, robotics, and increasingly for virtual reality, augmented reality, and the metaverse.[3]
The name "OpenUSD" came into common use in 2023, when stewardship of the technology moved to a multi-company alliance.[4]
Background and history
The composition techniques at the core of USD, which allow 3D "scene graphs" to be built up and edited without overwriting source data, evolved at Pixar across several generations of its proprietary tools, with the USD project itself initiated in 2012 around the time of the film Brave.[5][6] Pixar invented USD to manage the overwhelming complexity of many different APIs and file formats inside a single 3D production pipeline.[5] Recognizing that other studios faced the same problem, Pixar published the source code in 2016 under a modified Apache license so that the wider industry could extend and benefit from it.[2][3]
The first open release shipped alongside Hydra, a high-performance preview renderer able to display large data sets interactively, plus integration plugins for tools such as Autodesk Maya and Foundry Katana.[2] Software vendors including Autodesk and The Foundry committed to integration, and over the following years USD import and export spread to most major 3D applications.[2][3]
How USD works
USD organizes a scene as a hierarchical scene graph of objects (called prims). Its defining feature is composition: a final scene is assembled from multiple contributions that are combined according to well-defined rules, so that different artists and tools can edit the same scene in parallel without destroying one another's work.[3] The main composition mechanisms, known as composition arcs, are summarized below.[7]
| Composition arc | Purpose |
|---|---|
| Sublayers (layering) | Non-destructively stack multiple layers of scene data, with stronger layers overriding weaker ones. |
| References | Bring in (reference) another USD file or asset and reuse it within the current scene. |
| Payloads | A special kind of reference that can be loaded or unloaded on demand, for deferred loading of heavy content. |
| Variants and variant sets | Package switchable alternatives (for example different looks or states) that can be selected per scene. |
| Inherits | Establish class-like inheritance so that changes propagate to all instances. |
| Specializes | Provide fallback or specialized values that weaker opinions can refine. |
These arcs let a studio or platform express the same asset many ways and recompose it for different uses, which is why USD is often described as an authoring and interchange format rather than a simple geometry container.[7]
File formats
USD defines several on-disk encodings that share the same data model.[3]
| Extension | Description |
|---|---|
| .usd | A generic USD file that may use either the ASCII or the binary encoding. |
| .usda | Human-readable ASCII encoding. |
| .usdc | Binary encoding, known as the Crate format, optimized for size and fast loading. |
| .usdz | A package (an uncompressed ZIP archive) that bundles a USD file together with its textures, audio, and other assets into a single portable file. |
The .usdz package format is the encoding most associated with AR delivery, because it collects everything an asset needs into one self-contained file that is convenient to share and view.[3][8]
Alliance for OpenUSD
On August 1, 2023, Pixar, Adobe, Apple, Autodesk, and NVIDIA announced the Alliance for OpenUSD (AOUSD) to promote the standardization, development, evolution, and growth of Universal Scene Description.[4] The alliance was formed as a project of the Joint Development Foundation (JDF), an affiliate of the Linux Foundation, and aims to define written specifications for the technology and to drive greater interoperability of 3D tools and data across industries.[4][9] Steve May, Chief Technology Officer at Pixar, was named the initial chairperson.[4][9]
At launch, AOUSD organized work into specification efforts that grew over time into working groups covering the core specification, materials, geometry, and physics, with the materials and geometry groups added in March 2024 and a physics group in November 2024.[9] In December 2023 the alliance published a multi-year roadmap toward a formal core specification.[9] The alliance also collaborates with the Khronos Group on aligning OpenUSD with the glTF delivery format.[10]
By early 2026 the alliance reported momentum following ratification of the OpenUSD Core Specification 1.0, and welcomed additional members including Qualcomm Technologies, which highlighted a commitment to interoperability across the XR device ecosystem.[11]
Role in VR, AR, and the metaverse
OpenUSD has become a foundational technology for spatial computing because it provides a shared way to author and exchange the rich 3D scenes that VR and AR experiences require.[4]
NVIDIA Omniverse
NVIDIA Omniverse is built on OpenUSD; NVIDIA builds OpenUSD into its Omniverse libraries and frameworks and uses it as a common data layer for collaborative 3D workflows, digital twins, and simulation.[12] NVIDIA has positioned USD as a candidate common language for the open metaverse and the industrial metaverse.[13] Omniverse also added OpenXR support to extend its USD-based scenes to XR headsets.[14]
Apple visionOS and USDZ
The .usdz package format was introduced by Apple, developed together with Pixar, and announced at WWDC in June 2018 as the first file format for sharing 3D augmented reality content on Apple platforms, debuting with the AR Quick Look feature in iOS 12.[8] AR Quick Look lets users view USDZ models of virtual objects in 3D and place them in their real-world surroundings, with support for animation and audio, directly inside built-in apps such as Safari, Messages, Mail, News, and Notes on iPhone, iPad, and Apple Vision Pro.[15]
USD is central to Apple's spatial computing platform. When AOUSD was announced, Mike Rockwell, Apple's vice president of the Vision Products Group, said that "OpenUSD will help accelerate the next generation of AR experiences, from artistic creation to content delivery," and called USD "an essential technology for the groundbreaking visionOS platform, as well as the new Reality Composer Pro developer tool."[16] Reality Composer Pro uses USD's composition features to let multiple people work in parallel on 3D models, materials, and sounds, and to prepare assets authored in other applications for use in visionOS apps.[17]
Relationship to glTF
OpenUSD is generally treated as complementary to glTF, the runtime 3D asset transmission format maintained by the Khronos Group, rather than as a competitor.[10] An authoring format and a delivery format have different design goals: USD is built for flexibility, assembling many tools into sophisticated pipelines to create high-end content, while glTF is built to be lightweight, compact, and efficient to process and render at runtime on a wide range of platforms, down to web browsers on mobile phones.[18] In practice scenes are often authored and composed in USD and then delivered to end users as glTF, and AOUSD and Khronos have worked together to improve interoperability between the two so that content created in OpenUSD pipelines can be published through glTF.[10][18]
See also
References
- ↑ "OpenUSD". Pixar. https://www.pixar.com/openusd.
- ↑ 2.0 2.1 2.2 2.3 "Open Source Release". Pixar. 2016-07-26. https://openusd.org/release/press_opensource_release.html.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 "Universal Scene Description". https://en.wikipedia.org/wiki/Universal_Scene_Description.
- ↑ 4.0 4.1 4.2 4.3 4.4 "Pixar, Adobe, Apple, Autodesk, and NVIDIA Form Alliance for OpenUSD to Drive Open Standards for 3D Content". Joint Development Foundation. 2023-08-01. https://www.linuxfoundation.org/press/announcing-alliance-for-open-usd-aousd.
- ↑ 5.0 5.1 "Pixar's Universal Scene Description to be Open-Sourced". 2016-07-26. https://www.awn.com/news/pixar-s-universal-scene-description-be-open-sourced.
- ↑ "Introduction to USD". Pixar. https://openusd.org/release/intro.html.
- ↑ 7.0 7.1 "USD Glossary: Composition Arcs". Pixar. https://openusd.org/release/glossary.html.
- ↑ 8.0 8.1 "Apple Announces New USDZ Augmented Reality File Format Coming in iOS 12". 2018-06-04. https://www.macrumors.com/2018/06/04/apple-announces-usdz-file-format/.
- ↑ 9.0 9.1 9.2 9.3 "Alliance for OpenUSD". https://en.wikipedia.org/wiki/Alliance_for_OpenUSD.
- ↑ 10.0 10.1 10.2 "Building Bridges in 3D: AOUSD and Khronos Collaborate on OpenUSD and glTF Interoperability". https://www.khronos.org/blog/building-bridges-in-3d-aousd-and-khronos-collaborate-on-openusd-and-gltf-interoperability.
- ↑ "Alliance for OpenUSD Announces New Member Milestones and Industrial Momentum Following Core Specification 1.0". 2026-03-25. https://www.linuxfoundation.org/press/aousd_prmarch2026.
- ↑ "What Is OpenUSD and How It Works?". NVIDIA. https://www.nvidia.com/en-us/omniverse/usd/.
- ↑ "Universal Scene Description as the Language of the Metaverse". NVIDIA. https://developer.nvidia.com/blog/universal-scene-description-as-the-language-of-the-metaverse/.
- ↑ "Nvidia Omniverse gets spatial computing update with OpenXR support". 2023-08-08. https://mixed-news.com/en/nvidia-omniverse-gets-spatial-computing-update-with-openxr-support/.
- ↑ "Quick Look - Augmented Reality". Apple. https://developer.apple.com/augmented-reality/quick-look/.
- ↑ "Pixar, Adobe, Apple, Autodesk, and NVIDIA form Alliance for OpenUSD". Apple. 2023-08-01. https://www.apple.com/newsroom/2023/08/pixar-adobe-apple-autodesk-and-nvidia-form-alliance-for-openusd/.
- ↑ "Explore the USD ecosystem - WWDC23". Apple. 2023. https://developer.apple.com/videos/play/wwdc2023/10086/.
- ↑ 18.0 18.1 "Why glTF is the JPEG for the metaverse and digital twins". https://venturebeat.com/technology/why-gltf-is-the-jpeg-for-the-metaverse-and-digital-twins.