USD Considerations

SimReady 3D Art Asset Structure

Every SimReady 3D art asset is made up of a combination of USD files that reference one another, and provide flexibility when composed in various ways to suit a consumers’ needs. This also allows the consumer the ability to easily edit and version specific components independently; leveraging the power of USD composition arcs and modularity.

At its core, a SimReady 3D art asset contains the following set of component .USD files:

SimReady component files

Image of a typical SimReady 3D art asset with its various component USD files

Component Breakdown

Each SimReady 3D art asset is composed of 5 individual component files.

  1. [Asset_Name]_inst.USD - This is the core SimReady file and contains all of the static geometry and named OmniPBR/OmniGlass materials. This file gets referenced by both the core [Asset_Name].USD file and its physics file. Changing this core file will impact everything downstream.

    • Base Static Geometric Model information includes:

      • Static Geometry Primitives and XForms

      • Static Geometry UVs

      • Transform hierarchy

        • Render looks

        • All applied OmniPBR.MDL & OmniGlass.MDL materials

        • All Texture Map References

  2. [Asset_Name].USD - This file represents the entry point for non-PhysX enabled assets, and it is immediately useful for Omniverse simulations that do not require physics. It includes:

    • Reference to [Asset_Name]_inst.USD for all static geometry and materials

    • It holds all applied semantic labels on the 3D art asset reside within this file

  3. [Asset_Name]_tagged.USD - As the name implies, this file is designed to house all of the tagging information that makes a SimReady 3D art asset discoverable within searches. It is not intended to be used directly within a simulation or scene file, and is strictly used to store relevant metadata about the object that can be queried by Omniverse without having to load a 3D art asset itself into memory.

    • This file contains a copy of the same semantic labels found in the [Asset_Name].USD file

    • Tagging metadata for search

      • Descriptions

      • Tags

      • Versions

      • This file is extendable and can hold additional metadata as needed for quick retrieval

  4. [Asset_Named]_with_physx.USD - This file represents a SimReady 3D art asset that is immediately useful within Omniverse simulations that require physics. It is designed to reference the other .USD files while adding specific PhysX physics information to the file. It also holds all information that associates the original OmniPBR.MDL files with physical SimPBR.MDL materials.

    • PhysX simulation schemas and data

      • Rigid Body Schemas

      • Collision Properties

      • Baked Collision Meshes

        • Physical Material Assignments

        • Material properties should represent the visual materials assigned in - the [Asset_Named]_inst.USD

  5. [Asset_Name]_with_physx_tagged.USD (deprecating)

    • Asset Management metadata (similar to the [Asset_Name]_tagged.USD information) pertaining specifically to the Physx physics file

Component Hierarchy Diagram