Everything you could possibly want to know (and probably, to be honest, a fair bit more) about Objects.Geometry.Mesh

This table describes in technical terms what Objects.Geometry.Mesh is and isnt. However, there is a lot of alternate terminology and expectations between industries. so This page hopefully explains this table in a little more detail, aswell as the actual implementation of the Mesh object model.

Feature Supported?
Vertices Data ✅ position (x,y,z) : double, color(argb) : int, texture coordinates(u,v) : double
Non-Manifold Geo ✅ Fully supported
Complex/self intersection ✅ (supported, but may render/triangulate funny in some apps)
N-gons ✅ but since we rely on triangulation, there are performance concerns with large (n > 50) n-gons
Edge Loops ❌ only face loops
Inner loops ❌ Inner loops must be split/triangulated (see triangulation)
Normals & Tangents ❌ Calculated through CCW indices and shared vertices
Custom vertex data ❌ Not supported out of the box
Multiple render materials ❌ See #displayValues
NURBS/BREP/SPLINE/SDF ❌ Only polygon mesh data
Number of vertices/faces 32bit int max value (tho some host applications may be limited to 16)

vertices

Mesh.vertices stores a flat list of x,y,z vertices.

What do I mean by a flat list?, I mean the x, y, z components have been flattened into one big long list of doubles!

This means that the length of the list should always be a multiple of 3. It also means that mesh.vertices.Count gives you a value that is 3 times the number of actual vertices in that mesh. You should use mesh.VerticesCount for the actual number of vertices.

Note for developers not using .NET or Python SDK: this property is chunked, and you cannot guarantee that the size of a chunk will be a multiple of 3 (in fact, they aren’t by default)

faces aka indices/face loops/outer loops

Polygon faces can have an arbitrary number of vertices. The number of vertices we call the cardinality of the face, or simply n.

For tringles n = 3 , for quads n = 4, and anything higher we call “n-gons”.

Mesh.faces stores a flat list of ints to represent polygon faces.

The first int in each face represents the cardinality in the face (n), The next n ints are the vertex indices for that face.