> [!abstract] Summary > **GeomSubset** is a USD construct that lets you assign **different materials to different face groups of a single mesh** — without splitting it into separate prims. Strongly preferred over splitting prims for material assignment: keeps the scene graph clean and improves USD/Hydra performance. --- # What it is A **GeomSubset** is a face group **inside** a mesh prim that carries its own material binding (and other attributes). One mesh, multiple material assignments — no need to break the geometry apart. > [!tip] Best practice > **Always prefer GeomSubsets over splitting prims** for material assignment. Lower prim count = lighter USD = faster Hydra. --- # Examples ![[file-20241105232304485.png]] ![[file-20241105231951920.png]] --- # Why it matters for performance - High prim counts (hundreds of siblings) slow USD and Hydra noticeably. - Consolidating meshes and using GeomSubsets keeps the scene graph compact while preserving per-face material control. - See [[../TROUBLESHOOTING/SOLARIS General Optimisation|SOLARIS General Optimisation]] for related guidance. --- # 🔗 Related - [[../SOLARIS MOC|SOLARIS MOC]]. - [[SOLARIS PrimType|SOLARIS PrimType]]. - [[SOLARIS Scene graph details|Scene Graph details]]. - [[../TROUBLESHOOTING/SOLARIS General Optimisation|General Optimisation]]. - [[../../../../PROTOCOL/USD/Notes/USD KNOWLEDGE/USD terms and definitions|USD Terms & Definitions]].