CGAL users discussion list

Hi,

I'm trying to do a grey_level_image triangulation (like described in the 
on-line manual Chapter X) and output the result into a STL file.

The 3d image triangulation seems to work fine but I just don't get it how to 
extract the mesh faces (with their correct normal vector) to create the STL 
output. I do get something similar to what I expect but a lot of faces have 
inverted normal-vectors. Some faces are completely deteriorated.

Anyway, I'm not very familiar with the whole thing of geometric triangulation 
(not with CGAL either). I read a lot of manuals and CGAL Lib documentation, 
but this didn't help me to understand what would be the right soloution.

Here is how I tried to extract the surface triangles:

for ( CGAL::Surface_mesh_default_triangulation_3::Finite_facets_iterator i = 
tr.finite_facets_begin(); i != tr.finite_facets_end(); ++i) {
        Cell_handle h=i->first;

//         if ( h->next()->next()->next() != h) {
//             cerr << " format error: polyhedron in file is not 
triangulated." << endl;
//             exit( 1);
//         }
        Point p;
        Point q;
        Point r;

//ignore origin points
                int index=0;
                do {
                        p = h->vertex(index)->point();
                        ++index;
                } while ((p.x() < 0.1)&&(p.y() < 0.1)&&(p.z() < 
0.1)&&(index<5));
                do {
                q = h->vertex(index)->point();
                        ++index;
                } while ((q.x() < 0.1)&&(q.y() < 0.1)&&(q.z() < 
0.1)&&(index<5));
                do {
                r = h->vertex(index)->point();
                        ++index;
                } while ((r.x() < 0.1)&&(r.y() < 0.1)&&(r.z() < 
0.1)&&(index<5));

        // compute normal
                Vector n;
                n = CGAL::cross_product( q - p , r - p );
        Vector norm = n / sqrt( n * n );
        *p_out << "    facet normal " << norm << endl;
        *p_out << "      outer loop " << endl;
        *p_out << "        vertex " << p << endl;
                *p_out << "        vertex " << q << endl;
                *p_out << "        vertex " << r << endl;
        *p_out << "      endloop " << endl;
        *p_out << "    endfacet " << endl;
    }

Maybe someone could give me a hint about what I am doing wrong.

Is there a possibility to get the Surface Triangles of a Triangulation 
directly instead of iterating through the facet-cells?

Thanks a lot, Tobi