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 hygene” 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	core usd
🔑	Asset transforms shall be defined such that the asset is correctly positioned and oriented at the origin (0,0,0).	core usd
🔑	Transforms and pivots should be positioned at intuitive points on the asset to ensure expected behavior during placement and rotation.	core usd	Manual
🔑	All geometry shall be represented as mesh primitives using the UsdGeomMesh schema.	core usd
✅	Mesh geometry must be manifold	core usd	latest+
✅	Mesh topology must be valid	core usd	latest+
✅	Meshes should be positioned using transformations, not by embedding positions into point positions.	core usd
✅	Repeated occurrences of identically shaped objects should have identical mesh connectivity	core usd	Manual
✅	Normals should be authored to accurately represent the intended surface appearance.	core usd	Manual
⛔	UsdGeomMesh (that is not utilizing subdivision) needs to have normal attributes.	rtx
⛔	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
🚀	Use efficient mesh boundaries for performance	rtx
🚀	Meshes should maintain appropriate scale and boundary volumes	rtx
🚀	Meshes should not overlap unnecessarily	core usd
🚀	Meshes should not share the exact same space	core usd
🚀	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
🚀	Each vertex position should be unique	core usd	latest+
🚀	Avoid tessellating primitive shapes	core usd
🚀	Mesh topology should be without unused vertices, edges, or faces.	core usd	latest+
🚀	Faces should have non-zero area.	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
🚀	Use appropriate mesh count for scene	rtx