What is Universal Scene Description (USD)? #burningquestion

As USD is being adopted more and more around the globe, it’s important for artists to be familiar with what it can do.

Universal Scene Description, or USD, is a powerful scene encoding format for content creation that enables 3D applications to exchange assets using a common language. It gives artists the option to load only the portion that they need, instead of loading everything, saving time and processor. Most importantly, USD provides a universal language so that projects can be shared between multiple artists in various departments in different studios.^[2]

Key Things to Know about USD

It All Started with Brave

USD is the fourth generation of “composed scene description” for Pixar^[4]. Developed by Pixar and first used in the film Brave back in 2010, and is the heart of their 3D graphics pipeline^[1]. It is known as the Presto system and has been used on every Pixar feature since^[4]. Over the last decade, Pixar continues to mature, refine, and stabilize the code, releasing it as open source^[1].

USD is Highly Scalable and Efficient with Collaboration as a Core Feature

Because of these reasons, and the fact that it’s open source, USD has been widely adopted worldwide by software developers, 3D artists, game designers, AR Designers, and the metaverse.

USD allows artists to collaborate on complex projects with considerable detail and share huge files with little latency. “When multiple artists are working on a project, USD uses layers to separate out each user’s work and when figures out which change to apply to the final scene using each layer’s “opinion strength,” which is based on the characteristics of each user’s layer. This method takes advantage of the fact that USD files can be merged and manipulated by overlaying multiple files and folders into a single scene.”^[7] USD is the perfect tool for large-scale projects from animation studios.

Parallel Workflows

USD provides a Common Language between 3D Applications, allowing them to read the same data with different tools. This language is for “defining, packaging, assembling, and editing 3D data, facilitating the use of multiple digital content creation applications.”^[5] In other words, USD allows artists working in different departments, like animation, lighting, or layout can collaborate using different tools.

Speed

USD can quickly transmit very large projects with complex scenes with tens of thousands of pieces of geometry and shading through the pipeline. It’s speed comes from it’s consise format that bakes down all of these properties, allowing for efficiency in loading and processing.^[10] Because of this, and it’s scalability and efficient collaboration, USB

USD is an Agnostic Format

USD doesn’t require any specific filesystem or persistent storage.^[6] It uses Material prims, Shader prims, and UsdShade networks, so it’s also agnostic about the underlying shading and rendering system.^[7]

NVIDIA developed a language, Material Definition Language (MDL), which is open-source and defines the aspects of how materials function in USD.^[6] MDL simplifies shaders for preview and VR use. MDL has been adopted by Adobe, Chaos, and Epic’s Unreal Engine.

USD is Widely Adopted

Most 3D applications now support the USD format including Maya, 3ds Max, Cinema 4D, ZBrush, Nvidia Omniverse, Blender, Houdini, and more.^[3] Currently used by 3D and visual effects artists, game developers, and Metaverse developers, USD is also being adopted into other industries like architecture, robotics, manufacturing, and more.^[8]

USD Tutorials & Resources

Create 3D workflows with USD – Video from WWDC 2021

Introduction to USD

Reality Converter beta – From Apple’s Developer’s site: “The Reality Converter app makes it easy to convert, view, and customize USDZ 3D objects on Mac. Simply drag and drop common 3D file formats, such as .obj, .gltf, and .usd, to view the converted USDZ result, customize material properties with your own textures, and edit file metadata. You can even preview your USDZ object under a variety of lighting and environment conditions with built‑in IBL options.”

Universal Scene Description (OpenUSD): 4 Superpowers to Get You Started

From NVIDIA Developer, Aaron Luk, one of the founders of Pixar USD and a senior engineering energy for Omniverse, gives you 4 USD Superpowers to unlock the possibilities for 3D workflows.

A USD (Universal Scene Description) primer for ARTISTS

Matt from the Maya Learning Channel breaks USD down beautifully. He explains that USD will just take a change in mindset for 3D artists. He explains that if you have any interest in working at a big studio, you need to be familiar with USD. Most importantly, Matt gives you some terminology, such as Prims, or Primitive, the smallest unit in USD, and explains how it actually works.

See also, Maya-USD on GitHub

Sources/References

1. Pixar’s USD Pipeline, Renderman.Pixar.com.
2. USD Frequently Asked Questions, Graphics.Pixar.com
3. Universal Scene Description, Wikipedia.
4. Heritage of USD at Pixar, OpenUSD.org.
5. USD Shader Attributes, Referencing MDL Definitions in USD, NVIDIA Developer.
6. What You Need to Know About Universal Scene Description — From One of Its Founding Developers, NVIDIA Omniverse, Aaron Luk, Senior Engineering Manager, USD Ecosystem, February 16, 2023.
7. Unlocking collaborative workflows with USD, GarageFarm.NET.
8. What is a USD File? 3D Storage, Collaboration, and its Role in the Metaverse, by Sonia Schechter, CMO for 3D Cloud by Marxent.
9. What is Universal Scene Description?, NVIDIA Developer.
10. USD: what it is and why it matters, Ian Failes, Befores & Afters, December 11, 2019.

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