CGAL users discussion list

[Laurent Rineau <>]

On Wednesday 08 August 2007 18:21:27 Satyajit Sarangi wrote:
> Hi Laurent and Monique,
>           I am still having a problem when extracting the infinite cell.
> When trying to extract the triangles from the infinite cell, I tried both
> the incident cell approach as well as by iterating through all the cells
> and then taking into consideration only the infinite cells. Still the
> result seems to be the same in both the cases.

I do not understand what could be your problem. Do you use CGAL in debug 
mode, 
with assertions activated?

Can you insert
  CGAL_assertion(p_DelaunayTriangulation->is_valid());
at some point just before the code that tries to compute the convex hull?

If I had to bet, you would say that your code that displays triangles is the 
problem. On the picture, it seems that a lot of triangles have the point 
(0,0,0) as vertex.

If you need oriented triangles, use the function 
p_DelaunayTriangulation->triangle(celliteratorbegin, index), that will give 
you the triangles oriented inward. If you need triangle oriented to the 
outside, inverse the orientation:

    while (celliteratorbegin != celliteratorend) 
    {
        if (p_DelaunayTriangulation->is_infinite(celliteratorbegin))
        {
          const Triangle3D t = 
p_DelaunayTriangulation->triangle(celliteratorbegin,
 celliteratorbegin->index(p_DelaunayTriangulation->infinite_vertex());

          const Point3D pa = t[0];
          const Point3D pb = t[2]; // see the inversion here
          const Point3D pc = t[1];

          // then your code that push the triangle to your list
        }
        ++celliteratorbegin;
    }

-- 
Laurent Rineau
INRIA - Sophia Antipolis
BP 93, 2004 Route des Lucioles
06902 Sophia Antipolis Cedex FRANCE
Tel: +33 4 92 38 78 62