OpenUSD

Universal Scene Description

OpenUSD: An Overview

OpenUSD is a powerful, flexible, and extensible framework for representing, manipulating, and visualizing complex 3D scenes. It was developed and open-sourced by Pixar Animation Studios and is now used by numerous studios and companies worldwide.

Main Features of OpenUSD

• Scene Description: OpenUSD uses Universal Scene Description (USD) files to describe 3D scenes. These files can contain complex hierarchies of objects, along with their properties and relationships.

• Layering and References: USD files support a layering system, which allows multiple files to contribute to the final scene. This feature enables artists and technical directors to work on different aspects of a scene simultaneously.

• Performance: OpenUSD is designed to handle large scenes efficiently. It uses lazy loading and caching to keep memory usage low and support high-speed rendering and interaction.

• Extensibility: OpenUSD is highly extensible, allowing developers to add new object types, properties, and behaviors. This feature makes it possible to customize OpenUSD to fit specific production needs.

How OpenUSD Works

OpenUSD represents 3D scenes as a hierarchy of objects, known as prims. These prims can have various types, such as meshes, lights, or cameras, and they can be organized into parent-child relationships.

Each prim can have multiple properties, which describe its behavior and appearance. Properties can be simple values, like a mesh's color, or complex data structures, like a light's shadow map.

To create a scene, artists and developers can create and edit USD files, which are text files that describe the scene's prims and their properties.

For example, a USD file might contain the following:

#usda 1.0
def "World"
{
    def Sphere "MySphere"
    {
        double3 xformOp:translate = (10, 0, 0)
        uniform token[] xformOpOrder = ["xformOp:translate"]
    }
}

This file describes a scene with a single sphere, which is translated 10 units along the X axis.

OpenUSD in the Industry

Since its release, OpenUSD has been adopted by many companies in the VFX and animation industries. Its ability to handle large, complex scenes efficiently makes it ideal for high-end production work.

Some notable adopters of OpenUSD include:

• Pixar Animation Studios: Pixar uses OpenUSD extensively in their production pipeline. They use it to represent scenes in their films, from initial layout to final rendering.

• Industrial Light & Magic (ILM): ILM has integrated OpenUSD into their proprietary tools and workflows. They use it to manage complex scenes and assets for their visual effects work.

• DreamWorks Animation: DreamWorks has adopted OpenUSD as their primary scene description format. They use it to streamline their production process and increase collaboration between artists and technical directors.
• NVIDIA Omniverse

In conclusion, OpenUSD is a powerful tool for representing and manipulating 3D scenes. Its flexibility, performance, and extensibility make it an excellent choice for studios of all sizes.