Triangle Mesh

Represents a 3D object’s surface using vertices connected into triangular faces.

A triangle mesh is the most common surface representation in 3D graphics: a set of vertex coordinates plus an index of which three vertices form each triangle, together tracing out an object’s surface, optionally with normals, colors, and texture coordinates. GPUs render in units of triangles, so most 3D assets are stored as meshes, in formats like OBJ, STL, PLY, DAE, and glTF. Compared with a point cloud, a mesh has faces and connectivity, so it can be rendered and used for collision directly. Robot description files in URDF and MJCF use meshes to describe a link’s visual appearance and collision shape; but engines like MuJoCo only use a mesh’s convex hull for collision, so concave objects like cups and bowls need convex decomposition first. The outputs of 3D reconstruction and of the SMPL human body model are also meshes.

ExampleImporting a mug’s OBJ model directly into MuJoCo for collision treats it as a convex hull, which effectively “seals” the cup’s opening so a small ball can’t be dropped inside; only after decomposing it into several convex pieces with CoACD can objects actually be placed inside the cup.

Also called

Mesh, Polygon Mesh

Related

Point Cloud · Voxel · Mesh File (STL / OBJ / DAE / glTF) · Collision Geometry (Collider) · Convex Decomposition · Unified Robot Description Format

Sources

Wikipedia: Polygon mesh
MuJoCo XML Reference: asset/mesh（「collision detection works with the convex hull of the mesh」）