Add an algorithm to convert a surface mesh to a polyhedralsurface which preserves the topology (!730) · Merge requests · SFCGAL / SFCGAL

Description

At the moment, there are two algorithms which generate a polyhedralsurface from a cgal surface mesh:

extrude straight skeleton
split3D

The current mesh to polyhedral surface converter is quite simple: it converts each face into a patch. It works reliably, however, it has 2 side effects:

the resulted phs is triangulated: each patch is a triangle
the topology is not preserved. The phs does not contain any holes. The holes are visible but the polyhedralsurface is triangulated aroud the holes

This new algorithm preserves the tolopogy:

the output is not triangulated
the patches contain the holes

its implementation is quite simple:

perform a deep search to extract all the coplanar surfaces of the mesh. Each coplanar surface will be a patch
for each coplanar surface, extract the boundary cycles with PMP::extract_boundary_cycles:
- if there is only one cycle, this is the exterior ring of the patch
- if there are more than one hole, sort them by area. The largest one is the exterior ring. The other ones are the inner rings.