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# What is USD?

USD, or Universal Scene Description, is an open-source framework developed by Pixar Animation Studios. It is engineered for scalability and is designed to efficiently manage and describe large-scale 3D scenes and assets. USD enables pipelines to work collaboratively with assets and scenes, assembling, disassembling, reading, writing, editing, and exchanging complex 3D content between various applications seamlessly. It provides robust tools for referencing, layering, and composing scenes, ensuring both versatility and collaborative efficiency in production workflows.

Note: To learn more, see OpenUSD's Intro to USD.

# How USD Helps Lighting and Look Development

USD offers numerous advantages to VFX and animation studios, improving both collaboration and efficiency within their pipelines.

- Streamlined Asset Management - USD ensures consistent asset representation, simplifying shader, texture, and light rig management across various look dev and lighting tools. With many industry-standard tools adopting USD, such as Maya, Houdini, Mari, and Nuke, it becomes much easier to exchange 3D data between different applications and pipelines.

- Efficient Collaboration -The layering system also offers a neat way of dividing areas of responsibility across the pipeline. Multiple artists can work on the same scene simultaneously, with one working on one aspect (or area of the scene) while another focuses on a different task. When complete, the results can be published as layers into the same USD stage.

  USD's composition engine ensures that all changes are efficiently combined. This effectively eliminates the “waterfall” approach to production, where departments are dependent on the completion of work at the previous stage in the pipeline.

- Viewport Improvements- The Hydra rendering architecture alongside USD offers high-quality, real-time previews and supports various render engines. This enables look dev and lighting artists to receive instant feedback, making the iterative process more efficient.

- Variants - USD supports the concept of variants, which let you maintain multiple alternative representations or configurations of assets. They offer an organized way to dynamically switch between versions of the same asset, enabling flexibility in production. Variants are grouped into sets of related assets, allowing you to easily pick from the set. For example, you might have multiple clothing options for a character, or different levels of detail for a mesh to tailor complexity at different stages of the workflow.

- Scalability - USD is designed to handle complex scenes efficiently. This ensures that even when dealing with sophisticated lighting setups or intricate shaders, performance remains optimized.

- Asset Sharing and Interchangability - USD makes it easier to share assets between departments. A look dev artist can create a shader and, using USD, that shader can be consistently applied and viewed by artists in other departments, such as animation or layout.

- Payloads and Deferred Loading - Payloads enable artists to load only the required parts of the scene for their work. For example, a lighting artist can delay loading geometry, attributes, or layers until they are necessary. This reduces performance and memory usage when dealing with heavy assets.

- Rich Metadata - USD allows for storing metadata, which can be used for asset tracking, version history, automation tasks, and other important details about shading or lighting decisions.

- Proceduralism - Given USD's compatibility with procedural systems, it can facilitate dynamic changes. For example, adjusting a procedural shader parameter can change the look across multiple assets.

In general, USD's innovative approach to 3D graphics data interchange brings significant value to VFX and animation studios. It enables enhanced collaboration, non-destructive editing, a standardized format, asset reusability, and eliminates the restrictive waterfall workflow. USD revolutionizes every studio's workflows, leading to more efficient pipelines.

Note: To start learning how to build a USD scene, see Building USD Scenes.

Note: To see more about USD workflows in Katana, see USD Workflows - Choose your route.