Glossary for USD workflows section
Whether you're new to USD, working with Omniverse, or building digital twins, understanding the terminology is crucial for effective communication and learning. This comprehensive glossary covers every key term from the USD Tutorial Series, organized by category for easy navigation.
By the end of this reference, you'll have a clear understanding of all USD, Omniverse, and digital twin terminology used throughout the tutorial series.
Table of Contents
How to Use This Glossary
Quick Reference Format
Each entry includes:
Term - Clear definition
Context - Where it's used
Example - Practical application
See Also - Related terms
Difficulty Levels
🟢 Beginner - Essential concepts for newcomers
🟡 Intermediate - Technical implementation details
🔴 Advanced - Complex composition and optimization
USD Core Concepts
USD (Universal Scene Description) 🟢
Definition: Open-source framework developed by Pixar for describing, composing, and authoring 3D scenes and interchange between different tools and renderers.
Context: The foundation of the entire tutorial series; enables non-destructive, layered 3D workflows.
Example: A USD stage can combine geometry from Maya, materials from Substance, and animations from Blender in a single scene.
See Also: Stage, Prim, Layer, Composition Arcs
Prim (Primitive) 🟢
Definition: The basic building block of USD scenes; represents any object, group, or component in the scene hierarchy.
Context: Every element in a USD scene (geometry, lights, cameras, materials) is a prim.
Example: /World/Factory/Machine_001 - a hierarchical prim path representing a machine in a factory.
See Also: Stage, Prim Path, Scene Graph
Stage 🟢
Definition: The complete 3D scene composed from multiple USD layers and files; the final result of composition.
Context: What you see and work with in applications like Omniverse Composer or usdview.
Example: A factory floor stage combining building geometry, equipment, and lighting from different sources.
See Also: Layer, Composition, Root Layer
Layer 🟡
Definition: A single USD file that contains scene data; multiple layers compose together to create the final stage.
Context: Enables non-destructive editing by separating different types of data (geometry, materials, overrides).
Example: One layer for base geometry, another for materials, and a third for variant overrides.
See Also: Layer Stack, Sublayer, Root Layer
LIVRPS 🔴
Definition: The composition strength hierarchy (Local, Inherits, Variants, References, Payloads, Specializes) that determines which opinion wins when multiple sources define the same property.
Context: Critical for debugging composition conflicts and understanding why certain values appear in the final scene.
Example: A local transform (L) always overrides a referenced transform (R), regardless of layer order.
See Also: Composition Arcs, Opinion, Layer Stack
Composition Arcs 🟡
Definition: The mechanisms (references, payloads, variants, inherits, specializes) that combine multiple USD sources into a single stage.
Context: How USD achieves modularity and reusability across different files and assets.
Example: A reference arc brings in external geometry, while a variant arc switches between different material configurations.
See Also: LIVRPS, Reference, Payload, Variant
Reference 🟡
Definition: A composition arc that brings in data from another USD file or prim path.
Context: Enables modularity by allowing scenes to reference external assets.
Example: references = @bolt.usda@</Bolt> brings in a bolt model from an external file.
See Also: Payload, Composition Arcs, Asset
Payload 🟡
Definition: A composition arc similar to reference but with lazy loading - the data is only loaded when needed.
Context: Performance optimization for large scenes with heavy assets.
Example: Large CAD assemblies use payloads to load detailed geometry only when viewed.
See Also: Reference, Lazy Loading, Performance
Variant 🟡
Definition: A composition arc that provides switchable alternatives for a prim (different materials, LODs, configurations).
Context: Enables asset configuration without duplicating geometry.
Example: A car model with "red", "blue", and "green" paint variants.
See Also: Variant Set, LIVRPS, Asset
Variant Set 🟡
Definition: A collection of related variants that can be switched between.
Context: Organizes related alternatives (materials, LODs, configurations) in a logical group.
Example: A "color" variant set with "red", "blue", "green" options.
See Also: Variant, Asset, Configuration
Instancing 🟡
Definition: A system for efficiently reusing identical geometry by sharing a single prototype across multiple instances.
Context: Critical for performance in scenes with repeated elements (bolts, windows, furniture).
Example: 1000 identical bolts share one prototype, saving 99% of memory usage.
See Also: Prototype, Performance, Memory
Prototype 🔴
Definition: The shared internal prim that contains the data for all instances of an instanceable object.
Context: Created automatically by USD when prims are marked as instanceable = true.
Example: All instances of a bolt reference the same hidden prototype prim.
See Also: Instancing, Instanceable, Memory
Prim Path 🟢
Definition: The hierarchical address of a prim in the scene graph, similar to a file path.
Context: How you reference and locate specific objects in USD scenes.
Example: /World/Factory/ProductionLine_A/Machine_001/Bolt_025
See Also: Scene Graph, Prim, Hierarchy
Property 🟡
Definition: An attribute or relationship that belongs to a prim (transform, material binding, custom data).
Context: The actual data stored on prims - what makes them meaningful.
Example: xformOp:translate = (10, 0, 0) is a transform property.
See Also: Attribute, Relationship, Prim
Opinion 🔴
Definition: A value for a property coming from a specific layer or composition arc.
Context: USD's term for competing values that need resolution through LIVRPS.
Example: Two layers providing different materials for the same object create competing opinions.
See Also: LIVRPS, Composition, Layer Stack
Omniverse Platform
Omniverse 🟢
Definition: NVIDIA's real-time collaboration and simulation platform built on USD.
Context: The primary platform for working with USD in industrial and creative applications.
Example: Multiple users editing the same 3D scene simultaneously across different applications.
See Also: USD, Nucleus, RTX, Collaboration
Nucleus 🟡
Definition: Omniverse's centralized server that enables real-time collaboration, versioning, and asset management.
Context: The "collaboration brain" that keeps all users synchronized.
Example: A Nucleus server hosts shared assets and enables live collaboration across global teams.
See Also: Omniverse, Collaboration, Version Control
Omniverse Composer 🟢
Definition: General-purpose authoring application for creating and editing USD scenes.
Context: Primary tool for scene assembly, material assignment, and USD workflow management.
Example: Used to combine CAD imports, add materials, and set up variant systems.
See Also: Omniverse, USD, Authoring
Omniverse Create 🟡
Definition: Advanced authoring application with additional modeling and creative tools.
Context: More feature-rich than Composer, aimed at content creators and technical artists.
Example: Used for complex scene authoring, advanced material work, and creative workflows.
See Also: Omniverse Composer, Authoring, Creative Tools
RTX Renderer 🟡
Definition: NVIDIA's real-time ray tracing renderer integrated into Omniverse applications.
Context: Provides photorealistic rendering without time-consuming pre-computation.
Example: Real-time ray-traced reflections and global illumination for digital twin visualization.
See Also: Rendering, Ray Tracing, Photorealism
CloudXR 🔴
Definition: NVIDIA's cloud-based XR streaming service for deploying 3D content to any device.
Context: Enables instant XR experiences without local hardware requirements.
Example: Streaming architectural walkthroughs to mobile devices and headsets.
See Also: XR, Streaming, Cloud Computing
Connector 🟡
Definition: Plugin or integration that connects external applications (Maya, Blender, etc.) to Omniverse.
Context: Enables live sync between DCC tools and Omniverse workflows.
Example: Maya connector allows artists to work in Maya while changes sync to Omniverse.
See Also: Integration, DCC, Live Sync
File Formats & Extensions
USDA (USD ASCII) 🟢
Definition: Human-readable text format for USD files, useful for editing and debugging.
Context: Preferred for small files, debugging, and version control.
Example: Configuration files, variant definitions, and debugging sessions.
See Also: USD, USDC, Text Format
USDC (USD Crate) 🟡
Definition: Binary format for USD files, optimized for performance and file size.
Context: Preferred for large geometry files and production assets.
Example: Heavy CAD assemblies and final published assets.
See Also: USD, USDA, Binary Format
USDZ 🟡
Definition: Compressed USD format optimized for mobile and web delivery.
Context: Apple's preferred format for AR Quick Look and VisionOS applications.
Example: Product visualization on iOS devices and AR experiences.
See Also: USD, Mobile, AR
MDL (Material Definition Language) 🟡
Definition: NVIDIA's physically-based material description language used in Omniverse.
Context: Defines realistic material properties for RTX rendering.
Example: Automotive paint, metals, and complex layered materials.
See Also: Material, Shader, RTX
Composition & Architecture
Layer Stack 🟡
Definition: The ordered collection of layers that compose together to create the final stage.
Context: Determines the priority and combination of different data sources.
Example: Root layer → material layer → variant layer → session layer.
See Also: Layer, Composition, LIVRPS
Root Layer 🟡
Definition: The primary layer that defines the stage's structure and references other layers.
Context: The entry point for loading a USD stage.
Example: The main scene file that references all other assets and layers.
See Also: Layer, Stage, Sublayer
Sublayer 🟡
Definition: A layer that is composed into another layer, creating a layered hierarchy.
Context: Enables non-destructive editing and team collaboration.
Example: Adding a materials sublayer to a geometry layer.
See Also: Layer, Composition, Layer Stack
Session Layer 🔴
Definition: A temporary layer that holds ephemeral changes (UI selections, temporary overrides).
Context: Changes that shouldn't be saved to the persistent scene.
Example: Temporary material assignments during review sessions.
See Also: Layer, Temporary, UI
Inherits 🔴
Definition: A composition arc that applies class-based inheritance to prims.
Context: Enables object-oriented design patterns in USD.
Example: Multiple machines inheriting common properties from a machine class.
See Also: LIVRPS, Composition Arcs, Class
Specializes 🔴
Definition: A composition arc that creates specialized versions of base prims.
Context: Template-based inheritance for creating variations.
Example: Specialized versions of a base vehicle for different configurations.
See Also: LIVRPS, Composition Arcs, Template
Tools & Applications
usdview 🟢
Definition: Pixar's reference USD viewer and debugging tool.
Context: Essential for understanding USD composition and debugging issues.
Example: Inspecting layer stacks, viewing prototypes, and debugging composition conflicts.
See Also: USD, Debugging, Pixar
USDView 🟢
Definition: Same as usdview - Pixar's reference USD viewer (alternative spelling).
Context: Essential debugging and inspection tool for USD developers.
Example: Analyzing scene composition and validating USD structure.
See Also: usdview, Debugging, Inspection
Maya USD Plugin 🟡
Definition: Autodesk's official USD integration for Maya.
Context: Enables direct USD workflows within Maya for modeling and animation.
Example: Loading USD stages directly in Maya viewport for editing.
See Also: Maya, DCC, Integration
Blender USD Support 🟡
Definition: Built-in USD import/export and workflow support in Blender.
Context: Open-source DCC integration with USD workflows.
Example: Importing USD assets for modeling and exporting back to USD.
See Also: Blender, DCC, Open Source
Houdini Solaris 🔴
Definition: SideFX's USD-based context within Houdini for scene assembly and rendering.
Context: Professional USD workflows for complex scene assembly.
Example: Procedural scene assembly and USD-based lighting workflows.
See Also: Houdini, DCC, Procedural
ShapeFX Loki 🟡
Definition: Third-party USD viewer and editing tool based on OpenDCC.
Context: Alternative to usdview with additional features for USD workflows.
Example: USD file inspection and basic editing operations.
See Also: USD, Viewer, Third Party
Digital Twins & Industrial
Digital Twin 🟢
Definition: A virtual representation of a physical object or system that uses real-time data.
Context: Primary use case for USD in industrial applications.
Example: A virtual factory floor that mirrors the real production line with live sensor data.
See Also: IoT, Simulation, Manufacturing
IoT Integration 🟡
Definition: Connecting Internet of Things sensors and devices to USD-based digital twins.
Context: Enables real-time data visualization in 3D environments.
Example: Temperature sensors feeding live data to equipment visualizations.
See Also: Digital Twin, Real-time Data, Sensors
CAD Integration 🟡
Definition: Importing and working with Computer-Aided Design files in USD workflows.
Context: Essential for industrial and manufacturing applications.
Example: Converting SolidWorks assemblies to USD for digital twin creation.
See Also: CAD, Manufacturing, Import
Assembly 🟡
Definition: A collection of parts and components that form a complete product or system.
Context: Common structure in manufacturing and industrial USD workflows.
Example: A machine assembly with hundreds of bolts, brackets, and mechanical parts.
See Also: CAD, Manufacturing, Components
BIM (Building Information Modeling) 🟡
Definition: Intelligent 3D model-based process for architecture and construction.
Context: USD integration with architectural and construction workflows.
Example: Revit models converted to USD for real-time collaboration and visualization.
See Also: Architecture, Construction, Revit
Performance & Optimization
Lazy Loading 🟡
Definition: Deferring data loading until it's actually needed.
Context: Performance optimization technique used by payloads.
Example: Large CAD assemblies load only visible parts, improving startup time.
See Also: Payload, Performance, Memory
LOD (Level of Detail) 🟡
Definition: Multiple versions of an asset with different complexity levels.
Context: Performance optimization for real-time applications.
Example: High-detail model for close-up views, low-detail for distant views.
See Also: Performance, Optimization, Variants
Instancing 🟡
Definition: Reusing identical geometry efficiently by sharing data.
Context: Critical for performance in scenes with repeated elements.
Example: 1000 identical bolts using one shared prototype instead of 1000 copies.
See Also: Prototype, Memory, Performance
Streaming 🔴
Definition: Loading and displaying content progressively as needed.
Context: Enables working with massive datasets that exceed system memory.
Example: Large architectural models stream in detail as the camera moves.
See Also: Performance, Memory, Loading
Debugging & Troubleshooting
Yellow V Circle 🟡
Definition: UI indicator in Omniverse showing variant-related issues or conflicts.
Context: Common debugging scenario in USD workflows.
Example: Material variants not switching properly due to composition conflicts.
See Also: Debugging, UI, Variants
Blue I Circle 🟡
Definition: UI indicator in Omniverse showing inheritance-related issues.
Context: Debugging tool for composition problems.
Example: Class inheritance conflicts in complex USD hierarchies.
See Also: Debugging, UI, Inherits
Composition Conflict 🔴
Definition: When multiple sources provide different values for the same property.
Context: Common issue requiring LIVRPS understanding to resolve.
Example: Two layers assigning different materials to the same object.
See Also: LIVRPS, Debugging, Opinion
Material Binding 🟡
Definition: The process of assigning materials to geometry in USD.
Context: Common source of composition conflicts and debugging issues.
Example: Geometry assigned to different materials from different layers.
See Also: Material, Binding, Conflict
Validation 🔴
Definition: Checking USD files for errors, consistency, and compliance.
Context: Quality assurance for USD pipelines and workflows.
Example: Automated scripts checking for broken references and naming violations.
See Also: Quality Assurance, Pipeline, Automation
Industry & Applications
Manufacturing 🟢
Definition: Industrial production applications using USD for digital twins and visualization.
Context: Major use case for USD in industrial settings.
Example: Factory floor layouts, production line optimization, and equipment monitoring.
See Also: Digital Twin, Industrial, Production
Architecture 🟢
Definition: Building and construction industry applications using USD.
Context: USD workflows for architectural visualization and collaboration.
Example: Building information modeling and real-time design review.
See Also: BIM, Construction, Visualization
Entertainment 🟢
Definition: Film, games, and media applications using USD.
Context: USD's original domain, now expanding to other industries.
Example: Movie production pipelines and game asset workflows.
See Also: Film, Games, Media
XR (Extended Reality) 🟡
Definition: Virtual, Augmented, and Mixed Reality applications.
Context: USD enables efficient content delivery to XR devices.
Example: AR product visualization and VR training simulations.
See Also: VR, AR, Immersive
Simulation 🟡
Definition: Physics and behavior simulation integrated with USD scenes.
Context: Digital twin applications requiring dynamic behavior.
Example: Stress testing, fluid dynamics, and mechanical simulations.
See Also: Physics, Digital Twin, Analysis
Common Acronyms
USD 🟢
Universal Scene Description - The foundational technology
LIVRPS 🔴
Local, Inherits, Variants, References, Payloads, Specializes - Composition hierarchy
DCC 🟡
Digital Content Creation - Tools like Maya, Blender, Houdini
CAD 🟡
Computer-Aided Design - Engineering design tools
BIM 🟡
Building Information Modeling - Architectural design process
IoT 🟡
Internet of Things - Connected sensors and devices
XR 🟡
Extended Reality - VR, AR, and Mixed Reality
RTX 🟡
Real-Time Ray Tracing - NVIDIA's rendering technology
LOD 🟡
Level of Detail - Performance optimization technique
API 🔴
Application Programming Interface - Software integration interface
MDL 🔴
Material Definition Language - NVIDIA's material system
GPU 🟡
Graphics Processing Unit - Hardware for rendering and computation
Quick Reference Cards
File Extensions Quick Reference
.usda- USD ASCII (human-readable).usdc- USD Crate (binary, optimized).usdz- USD ZIP (compressed for mobile).mdl- Material Definition Language
LIVRPS Priority Order
Local - Direct edits (highest priority)
Inherits - Class-based inheritance
Variants - Switchable alternatives
References - External file inclusion
Payloads - Lazy-loaded external files
Specializes - Template inheritance (lowest priority)
Common Tools
usdview - USD inspection and debugging
Omniverse Composer - Scene authoring
Maya USD - DCC integration
Nucleus - Collaboration server
Performance Tips
Use instancing for repeated geometry
Use payloads for large assets
Use LOD variants for optimization
Use USDC for production files