Let’s start the year with something long overdue: The Alliance for OpenUSD (AOUSD) has released OpenUSD Core Specification 1.0, establishing the first formally ratified, production-ready core standard for OpenUSD. The specification defines the foundational behavior of OpenUSD, including how scene data is structured, composed, resolved, and exchanged across tools.
Rather than introducing new features, the Core Specification documents and standardises existing OpenUSD fundamentals as a normative reference. Its stated purpose is to reduce ambiguity between implementations and provide a shared baseline for interoperability across DCCs, engines, and pipeline tools.
A normative foundation for OpenUSD
According to AOUSD, Core Specification 1.0 defines the minimum required behavior software must implement to claim OpenUSD compliance. This includes formal rules for syntax, composition, and deterministic value resolution. By moving these definitions from implicit behavior to an explicit specification, AOUSD aims to reduce fragmentation and ensure that OpenUSD scenes behave consistently when transferred between applications. The specification is explicitly positioned as foundational, with future standards expected to build on top of it rather than redefining core mechanics.
What the Core Specification defines
OpenUSD Core Specification 1.0 standardises six core technical areas.
- It defines grammar and data types, specifying the formal language rules and primitive data representations used by OpenUSD.
- It introduces a document data model that describes how scene data is structured independently of file format.
- The specification provides a normative description of the composition algorithm, defining how multiple USD layers are combined non-destructively into a composed scene.
- It formalises stage population and value resolution, ensuring predictable construction of scene graphs and deterministic resolution of authored values.
- It defines file format specifications for USDA, USDC, and USDZ, covering text-based, binary, and packaged OpenUSD data.
- Finally, it introduces a compliance framework with conformance criteria and reference tests that allow developers to validate implementations against the specification.
Implications for production pipelines
For studios and pipeline developers, the Core Specification provides a clear technical contract for OpenUSD behavior. Tools that conform to the specification should interpret layering, composition, and value resolution in the same way, reducing ambiguity when assets move between applications.
The scope of the release is intentionally limited. The Core Specification does not define materials, animation semantics, physics, or rendering behavior. These areas are expected to be addressed by future AOUSD working groups through layered specifications built on top of the core.
Compliance and roadmap
Alongside the specification, AOUSD provides compliance tests and reference materials intended to support validation of conforming implementations. This enables vendors to verify behavior against a shared standard rather than relying on informal compatibility.
AOUSD has indicated that future revisions will extend the specification incrementally while maintaining compatibility with Core Specification 1.0. Follow-up releases are expected to refine compliance testing and expand coverage without altering the foundational behavior defined in this release.
With Core Specification 1.0, OpenUSD transitions from a widely adopted technology to a formally standardised foundation, establishing a stable base for vendor-neutral interoperability across 3D production pipelines.
AOUSD Official Announcement
https://aousd.org/news/core-spec-announcement/
AOUSD Blog: Foundations of Open 3D Development
https://aousd.org/blog/foundations-of-open-3d-development-introducing-aousd-core-specification-1-0/
