CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

The output to the polyhedron is triangulated and nef simplify planar 
facets probably.

The fact that facets are triangulated in the polyhedron is a bug.
I added it to my TODO list and will post the fix here when done.

Sebastien.


On 10/29/2013 08:52 PM, KeithSloan52 wrote:
> I am new to CGAL and not really understanding, just following examples.
>
> I am testing some code with a hull or two cubes.
>
> When I try an iterate around the resulting facets, I just get facets with 3
> vertex where as if I look at the same input data with OpenSCAD ( That uses
> CGAL ) I see mostly facets with 4 vertex, so wondering what I am doing
> wrong.
>
> relevant sections of code are
>
>          typedef CGAL::Simple_cartesian<double>     Kernel;
>          typedef Kernel::Point_3                    Point_3;
>          typedef CGAL::Polyhedron_3<Kernel>         Polyhedron;
>          typedef Polyhedron::Vertex_iterator        Vertex_iterator;
>          typedef Polyhedron::Facet                  Facet;
>          typedef Polyhedron::Facet_iterator         Facet_iterator;
>          typedef Polyhedron::Halfedge_handle        Halfedge_handle;
>          typedef Polyhedron::Halfedge_around_facet_circulator
> Halfedge_around_facet_circulator;
>
>          // Define Vector of Vertexes
>          std::vector<Point_3> points;
>          // define polyhedron to hold convex hull
>    //Polyhedron_3 poly;
>          Polyhedron poly;
>
>          // compute convex hull of non-collinear points
>          CGAL::convex_hull_3(points.begin(), points.end(), poly);
>
>          len = poly.size_of_vertices();
>    std::cout << "The convex hull contains " << len << " vertices" <<
> std::endl;
>
>          Facet_iterator bfi = poly.facets_begin();
>          for ( ; bfi != poly.facets_end(); ++bfi)
>              {
>              cout << "Facet :" << endl;
>              Halfedge_around_facet_circulator j = bfi->facet_begin();
>              // Facets in polyhedral surfaces are at least triangles.
>              //CGAL_assertion( CGAL::circulator_size(j) >= 3);
>              //cout << "Start Vertex :" << j->vertex()-> point() << endl;
>              do {
>                 cout << "Vertex : " << j->vertex()-> point() << endl;
>                 } while ( ++j != bfi->facet_begin());
>              }
>
> If I look at the code OpenSCAD is using, I see that they immediately convert
> the polyhedron to a Nef polyhedron, but I don't understand the difference
> between the two.
>
>
>
> --
> View this message in context: 
> http://cgal-discuss.949826.n4.nabble.com/Convex-Hull-3D-Reposted-tp4658329.html
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