CGAL - Boost create undirected graph

Question

I've created a 3D Volume mesh using Cgal's documentation and I was succesfully able to visualize my c3t3 (Complex 3 in triangulation 3) object. The mesh is composed of several connected components the number of which i want to find using boost.

Dealing with c2t3 (cimplex 2 in triangulation 3) in the past i iterated over the vertices of the, make pairs with a vertex_descriptor and then again iterate over the edges finding the vertices and by using add_edge i created the undirected graph and finally return the number of c.c.

Now, the c3t3 object only provides iterators about vertices nad cells (not edges - only can be implicitly found). Can you help me pass the c3t3 object to a graph structure of Boost?

So far i did:

for (Cell_iterator c_it=c3t3.cells_in_complex_begin(); c_it != c3t3.cells_in_complex_end(); ++c_it)
{

  Vertex_descriptor vd1 = boost::add_vertex(graph);
  Vertex_descriptor vd2 = boost::add_vertex(graph);
  Vertex_descriptor vd3 = boost::add_vertex(graph);
  Vertex_descriptor vd4 = boost::add_vertex(graph);

  C3t3::Vertex_handle v0 = c_it->vertex(0);
  C3t3::Vertex_handle v1 = c_it->vertex(1);
  C3t3::Vertex_handle v2 = c_it->vertex(2);
  C3t3::Vertex_handle v3 = c_it->vertex(3);

  vertex_id_map.insert(std::make_pair(v0, vd1));
  vertex_id_map.insert(std::make_pair(v1, vd2));
  vertex_id_map.insert(std::make_pair(v2, vd3));
  vertex_id_map.insert(std::make_pair(v3, vd4));
}

Now i have to create the edges but i don;t know where to find the correct edges correspond to my c3t3 object.. Thank you for your help in advance

You have not reacted to the answer from Michael Simbirsky. Has it answered your question? — lrineau

Michael Simbirsky Michael Simbirsky · Accepted Answer · 2013-12-01T05:44:39

CGAL provides "Boost Graph adapters" for many of its classes (at least for triangulations, arrangements and for polyhedral surfaces). See more details in CGAL BGL page.

Essentially all DCEL- or similar structures can be viewed as a combination of two graphs, "primary" for vertex-edge relationships and "dual" for cell-edge relationships; CGAL provides Boost graph adapters for both.

If this out-of-box graphs are not good for you, than you have to answer your central question: how do you iterate over edges of a given cell (i.e. over edges of the "dual" graph) or over edges of a given vertex (i.e. over edges of the "primal" graph).

CGAL - Boost create undirected graph

1 Answers