IDs of the neighboring triangles or tetrahedra, returned as
a matrix. The elements in TN(i,:) are the neighbors
associated with ti(i).

By convention, TN(i,j) is the neighbor opposite
the jth vertex of ti(i). If
a triangle or tetrahedron has one or more boundary facets, the nonexistent
neighbors are represented as NaN values in TN.

Definitions

Triangle or Tetrahedron ID

A row number of the matrix, TR.ConnectivityList.
Use this ID to refer a specific triangle or tetrahedron.

Vertex ID

A row number of the matrix, TR.Points. Use
this ID to refer a specific vertex in the triangulation.