CGAL users discussion list

["Louis Feng" <>]

Hello,

I'm trying to construct a 2D triangle mesh from a list of vertices and
faces. I didn't want to use Polyhedron because I needed some properties from
the 2D triangulation class. I'm using Triangulation_2 and
Triangulation_data_structure_2. Basically I use T.tds() to get a reference
to the internal data structure. Then I add vertices and faces to it. But
this has become very confusing and I couldn't find examples on this.

An outline of my code:

triDS.set_dimension(2);
for(...) {
  VertexHandle vHandle = triDS.create_vertex();
  vHandle->set_point(Point2(...));
}
for(...) {
  FaceHandle fHandle = triDS.create_face(vHandle1, vHandle2, vHandle3); }

When I check triDS.is_valid() at the end, it returns false. More
interestingly, before I add anything to triDS, when I check the vertices,
edge, etc. I get this 

Triangulation vertices: 0
Triangulation faces: 1
Triangulation full faces: 1
Triangulation edges: 1

So am I suppose to clear this before I add something to it? Looking at the
template file for the data structure, it check this:

case 2:
    result = result &&  edge_count == 3*face_count/2 ;
    CGAL_triangulation_assertion(edge_count == 3*face_count/2);
    break;

I'm not sure what the expected behavior is. Could someone tell me what I'm
doing wrong and how this class suppose to be used? Thanks!

Louis