For as long as we have been creating digitally synthesized images, we have needed ways to describe the 3D scenes we are synthesizing in a way that is mathematical enough for computers to understand, but which is also understandable and manipulatable by technologists and artists.

This article tells the story of some of the challenges Pixar faced in describing, sharing, and transporting 3D scenes as our pipeline evolved over 25 years, from creating the first feature-length computer animated movie, to making it possible for our productions' artistic visions to keep growing in richness and collaboration. Thus, we present Universal Scene Description (USD), Pixar's open-source software for describing, composing, interchanging, and interacting with incredibly complex 3D scenes.

USD is a cornerstone of Pixar's pipeline and has been on a rapid and broad adoption trajectory, not only in the VFX industry, but also for consumer/Web content and game development.

When Pixar set out to make Toy Story in the early '90s, we had industry-leading, commercially-available products at the front and back of our 3D pipeline - Alias' PowerAnimator at the front for modeling, and Pixar's own RenderMan at the back. But to handle the scale of making a feature-length animation, we needed to invent or improve a suite of custom tools and data formats for everything that needed to happen between modeling and rendering.

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