CGAL users discussion list

[Daniel Abler <>]

Dear All,

I would like to create a Mesh_Domain_3, and subsequently a 
Mesh_complex_3_in_triangulation_3, from multiple polyhedral surface meshes 
(Polyhedral_3) so that each Polyhedral becomes one subdomain in the new 
Mesh_complex_3_in_triangulation_3. 
Some of the polyhedral surface meshes have common boundaries (i.e. vertices 
at same coordinates), none of them intersect. 

I tried two approaches, but neither of them solves my problem... Being new to 
CGAL, I am somewhat overwhelmed by the library and would really appreciate 
any pointer in the right direction.


My attempts so far:

1) Polyhedral_mesh_domain_3

Has an undocumented  (CGAL 4.6) constructor
 Polyhedral_mesh_domain_3(
                                InputPolyhedraPtrIterator begin,
                                InputPolyhedraPtrIterator end,
                                const Polyhedron& bounding_polyhedron,
                                CGAL::Random* p_rng = NULL)
that allows creation of a Polyhedral_mesh_domain_3 from an iterator over 
pointers to Polyhedrons:

std::list<Polyhedron*> poly_pointer_list = [...]
Polyhedron * bounding_surface_polygon = [...]
Mesh_domain domain(poly_pointer_list.begin(),poly_pointer_list.end(), 
*bounding_surface_polygon);
C3t3 c3t3 = CGAL::make_mesh_3<C3t3>(domain, criteria, no_exude(), 
no_perturb());

This results in a single domain, comprising the enclosed volumes of all 
Polyhedrons in poly_pointer_list. Also, an using the same approach with  
Polyhedral_mesh_domain_with_features_3.h seems not to be possible.

Once the MeshDomain is created, it should be possible to tag the faces of 
each sub-polyhedron with different MeshDomain_3::Surface_patch_index, as had 
been suggested in a previous post:
http://cgal-discuss.949826.n4.nabble.com/3D-mesh-creation-Mesh-complex-3-in-triangulation-3-from-multiple-polyhedral-surface-meshes-Polyhedro-td4660833.html#a4660876

Would this solve the problem and is there an example available for such 
construction?


2) Labeled_mesh_domain_3 with customised 
Polyhedral_to_implicit_labeling_function_wrapper following discussion thread: 
http://cgal-discuss.949826.n4.nabble.com/How-to-mesh-multiple-domain-multiple-Polyhedrals-td4659743.html

This makes use of CGAL/Mesh_3/polyhedral_to_labeled_function_wrapper.h for 
creation of  Labeled_mesh_domain_3  from Polyhedrons. 
An additional wrapper allows multiple Polyhedrons (wrapped by 
polyhedral_to_labeled_function_wrapper) to be passed to Labeled_mesh_domain_3.

This approach works in principle but becomes very slow for larger volumes and 
multiple submeshes. 
Also it seems that the meshing procedure does not terminate when the bounding 
box has been chosen too small.


Many thanks in advance for any hints towards improving either of those 
approaches or another alternative method for Mesh creation from multiple 
polyhedrons.

daniel