Figure 4
From: An ordered topological representation of 3D triangular mesh facial surface: concept and applications

Ordered pattern extraction (a) Three concentric facet rings in an ideal mesh. (b) Three concentric rings in mesh surface from which we derived cross patterns in the directions 9-3/7-1, 1-7/11-5, and 9-3/11-5. (c) Four quadrant grids facets constructed around a root facet in a ideal mesh. (d) An example of a grid composed of four quadrants extracted from a triangular mesh surface.