wtf is openusd?

This repository is a study guide for a professional certification exam on OpenUSD. OpenUSD, short for Universal Scene Description, is an open source framework first developed at Pixar for describing complex three dimensional scenes in a way that many artists and many software packages can work on the same scene without stepping on each other. The README is written as a series of short modules that walk through the concepts the exam is known to test. The early modules introduce the basic building blocks. A Stage is the loaded scene, inside it lives a Scenegraph, a tree of items called Prims with paths that look like file paths. Prims hold Attributes, the named values such as a sphere's radius or a mesh's points, and Relationships that point at other prims. Schemas are blueprints that say what a particular kind of prim is supposed to contain, with familiar examples being meshes, materials, and lights. A large section is devoted to composition, which the author flags as the heaviest part of the test at twenty three percent. Composition is the rule set that decides how data spread across many small files is layered together into one final scene. There is a memorable strength ordering, given the mnemonic LIVERPS, that ranks the different ways one file can pull in or override another: local opinions, inherits, variants, references, payloads, and specializes, from strongest to weakest. Further sections cover asset structure, instancing for efficient duplication, building pipelines that convert formats like FBX or Alembic into USD, debugging with the usdview viewer, and exam strategy tips for each blueprint topic. The full README is longer than what was shown.