Geometry

Overview

This capability provides requirements for the rendering of 3D surfaces in visualization systems, proper mesh topology and geometry for physics simulation, as well as placement, orientation and positioning.

Summary

• Geometry is most often represented as a UsdGeomMesh prim.

• Performance and proper “topological hygiene” is a key consideration for geometry and an important focus of this capability.

• USDGeom also provides other types of geometry, but this documentation focuses on meshes.

• Various other geometry types in USD are also “point based” and may share the same requirements as meshes.

Requirements

Tags	Summary	Compatibility	Validator
🔑	Assets must contain at least one imageable geometry prim.	core usd	latest+
🔑	Geometry shall be defined as such that the asset is correctly positioned and oriented at the origin (0,0,0).	core usd
🔑	All geometry shall be represented as non-subdivided mesh primitives using the UsdGeomMesh schema.	core usd	latest+
✅	Mesh geometry must be manifold	core usd	latest+
✅	Mesh topology must be valid	core usd	latest+
✅	Meshes should be positioned using xform ops, not by embedding positions into point positions.	core usd	latest+
✅	Repeated occurrences of identically shaped objects should have identical mesh connectivity	core usd	Manual
✅	All non-subdivided meshes must have normals.	core usd	latest+
✅	Mesh normals values must be valid to produce correct shading.	core usd
✅	The winding order of faces in a mesh must correctly represent the orientation (front/back) of the face.	core usd
✅	Meshes made from non opaque materials shall have thickness	core usd
⛔	World space bounds must not exceed RTX limit.	rtx	latest+
🚀	Boundable geometry primitives should have valid extent values.	openusd	latest+
🚀	Only include geometry that contributes to visualization or simulation	openusd	latest+
🚀	Use efficient mesh boundaries for performance	rtx
🚀	Meshes should maintain appropriate scale and boundary volumes	rtx	latest+
🚀	Meshes should not overlap unnecessarily	core usd
🚀	Meshes should not share the exact same space	core usd	latest+
🚀	Use indexed primvars when values are repeated	core usd	latest+
🚀	Do not subdivide meshes with Normals.	core usd	latest+
🚀	Only include primvars that are actively used	core usd	latest+
🚀	Combine small meshes into larger ones where appropriate	core usd
🚀	Use appropriate tessellation density for geometry	core usd
🚀	Use time samples only when attribute values change	core usd	latest+
🚀	Each vertex position should be unique	core usd	latest+
🚀	Avoid tessellating primitive shapes	core usd	latest+
🚀	Mesh topology should be without unused vertices, edges, or faces.	core usd	latest+
🚀	Faces should have non-zero area.Faces where all vertices are co-linear or coincident waste memory and can cause rendering artifacts.	core usd	latest+
🚀	The values of points must not exceed the limit at which a given precision can be represented using 32-bit floats.	core usd	latest+
🚀	Use appropriate vertex count for geometry	core usd
🚀	Meshes should use instancing if they are identical apart from their world space location	core usd	latest+
🚀	Boundable geometry should have non-zero extents in at least one dimension.Zero extent geometry wastes memory and may cause simulation problems.	core usd
🚀	Faces should not be lamina.Lamina faces are those that share all the same vertices. This means there are two or more identical overlapping faces. This is wasteful, and can also cause rendering artifacts if the faces have different materials. They can be created in a variety of ways, for example accidentally duplicating faces on a mesh, merging objects with coincident faces and then merging vertices, or modeling operations like booleans on meshes that have coincident faces.	core usd	latest+
🚀	Use appropriate mesh count for scene	rtx