# USD > [!abstract] About > Entry point for everything **USD** (Universal Scene Description) in the PROTOCOL pipeline. Covers theory, glossary, file formats, advanced courses, studio-scale references, performance optimization, and practical workflows (environment setup, file conversion, `.usda` analysis, memory allocator tuning). ## 🧭 Reading Order for Newcomers 1. [[Notes/USD KNOWLEDGE/6.30 USD Theory|6.30 USD Theory]] — the *why* and core concepts (layers, prims, variants, purposes, kinds, components, assemblies, payloads, layer stack). 2. [[Notes/USD KNOWLEDGE/USD terms and definitions|USD terms and definitions]] — quick glossary to fix vocabulary. 3. [[Notes/USD KNOWLEDGE/USD Extension|USD Extension]] — `.usd` / `.usda` / `.usdc` / `.usdz` trade-offs. 4. [[Notes/USD Practice/USD Analysing usda files|USD Analysing usda files]] — read a real `.usda` to make the theory concrete. 5. [[Notes/USD KNOWLEDGE/USD From 0 to pro - L4 WS|USD From 0 to pro — L4 WS]] — extended course: history, four pillars, toolset, languages. 6. [[Notes/USD KNOWLEDGE/ANIMAL LOGIC use of USD|ANIMAL LOGIC use of USD]] — studio-scale example. 7. [[Notes/USD Practice/USD Maximizing Performance - by pixar|USD Maximizing Performance — by Pixar]] — optimization once the fundamentals are in place. ## 📚 Fundamentals - [[Notes/USD KNOWLEDGE/6.30 USD Theory|6.30 USD Theory]] — layers, variants, sublayers vs references, stage, prims, opinions, purpose/kind, components vs assemblies, payloads, layer stacks. - [[Notes/USD KNOWLEDGE/USD terms and definitions|USD terms and definitions]] — concise glossary of core USD terms with code examples. - [[Notes/USD KNOWLEDGE/USD Extension|USD Extension]] — when to use ASCII vs binary vs packaged formats. ## 🎓 Advanced Theory - [[Notes/USD KNOWLEDGE/USD From 0 to pro - L4 WS|USD From 0 to pro — L4 WS]] — history, non-destructive composition, parallel workflow, four pillars, composition, toolset, C++/Python/USDA. - [[USD Survival Guide - Lucas Scheller]] — external survival guide reference. ## 🏢 Studio References - [[Notes/USD KNOWLEDGE/ANIMAL LOGIC use of USD|ANIMAL LOGIC use of USD]] — entity-fragment architecture at scale. — PDF on USD-at-scale production workflows. ## ⚙️ Optimization - [[Notes/USD Practice/USD Maximizing Performance - by pixar|USD Maximizing Performance — by Pixar]] — Pixar's performance guidance. - [[Notes/USD Practice/USD Jemalloc use|USD Jemalloc use]] — memory allocator: why it matters for USD/Houdini on Linux vs Windows 11. ## 🛠️ Practice - [[Notes/USD Practice/USD Environment Setup|USD Environment Setup]] — USD environment variables and initial setup. - [[Notes/USD Practice/USD Convert from USDC to USDA|USD Convert from USDC to USDA]] — command-line conversion between USD file formats. - [[Notes/USD Practice/USD Analysing usda files|USD Analysing usda files]] — reading and interpreting a `.usda` file. ## 📖 Resources - [[USD Ressources]] — external links, tutorials, and reading list. ## 🔗 Related - [[../../THE PROTOCOL VAULT|THE PROTOCOL VAULT]] — root of the PROTOCOL pipeline documentation.