Draft REP 158 standardizes OpenUSD for cross-platform robot simulation

The ROS community has opened Draft REP 158 for public discussion, proposing a standard way to use OpenUSD (Universal Scene Description) for simulation asset interoperability. The proposal addresses a critical gap: while URDF and SDF serve ROS well, OpenUSD has become a broader industry standard for Physical AI, but lacks standardized semantics for ROS concepts like TF trees. Without regulation, its flexibility could lead to proprietary extensions and fragmentation. The REP defines four pillars: a standardized asset baseline (mandating MKS units, Z-up coordinates, and a modular Extract-Transform-Load structure that separates visual, physics, and simulator-specific layers); declarative ROS interface schemas (engine-agnostic schemas like RosContextAPI for topics, services, actions, and frames); export and conversion rules (guaranteeing down-conversion to glTF 2.0 and URDF with standard PBR materials); and ecosystem tooling including a community registry and a compliance checker.

Community feedback has already raised practical concerns. For instance, user khalidbourr highlighted the asymmetry between unsupported visual features (which can be safely ignored) and unsupported physics properties (which silently change behavior, e.g., concave mesh collisions approximated as convex hulls). The REP will need to address how simulators signal what they dropped or approximated. Proponents argue that this standard is essential for interoperable simulation in ROS, enabling assets to be built once and used across Gazebo, O3DE, Isaac Sim, Newton, MuJoCo, and Genesis. By isolating proprietary extensions into optional layers and mandating compliance checks, the REP aims to prevent vendor lock-in while fostering a collaborative ecosystem for robotics simulation.