Advanced guide to 3D Materials

A 3D object is made of digital data intended to recreate a surface in relief. This surface is rendered by a mesh composed of polygons, in particular triangles and quads.

diagram of the composition of a 3D polygon

A mesh is therefore made of faces, edges and vertices, and can be more or less complex depending on the number of polygons it is made of.

For technical reasons, only quads and triangles are used when creating a 3D mesh. Any polygon with more than 4 vertices, also called an N-Gon, must be avoided.

What is a 3D mesh topology?

The topology of a 3D surface refers to the organisation of edges and vertices within a mesh. A bad topology can cause errors as well as various problems when editing your 3D model (particularly if the model contains N-Gons or Loose points).

Conversely, a good topology allows for faster and cleaner work when editing and deforming a 3D mesh.

What makes a good topology

A topology considered good is mostly composed of quads (which greatly facilitates so-called “manual” modelling work, unlike triangles) and contains Loops.

A loop is a set of faces and edges which, once selected, forms a continuous loop. These loops allow a segment of the 3D model to be selected quickly, and prove very useful for models containing many polygons.

A model containing good loops will deform better once animated, and will be simpler to handle when editing certain parameters.

How to work with the topology of scanned objects

Typically, meshes generated by digitising objects from point clouds are considered bad topologies.

Indeed, the topology is generated according to algorithms built from the information recognised in the point cloud. It can also turn out to be Non-Manifold.