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[Andre Massing <>]

Hi all!

I guess it is probably just a matter of my lacking comprehension, but I have 
difficulties to interpret the outcome of a Polyhedron to Nef_polyhedron 
conversion. I startet with the four points of the "unit" or standard 
tetrahedron, built up a tetrahedron via the make_tetrahedron member function 
of the Polyhedron class and after that created a Nef_polyhedron. When I 
iterate over the points by the attached code, it gives me output like

Source point -0 -1 1
Target point -0 -1 -0

which confuses me because the tetrahedron was defined by (0,0,0), (1,0,0), 
(0,1,0) and (0,0,1) as the iteration over the vertices of the polyhedron also 
shows (beside the strange minus in front of 0) How to I have to intepret 
this? 
Demostrating code is attached.

Any enlightment are highly appreciated!
Andre
#include <CGAL/Exact_predicates_exact_constructions_kernel.h>
#include <CGAL/Nef_polyhedron_3.h>
#include <CGAL/Polyhedron_3.h>

typedef CGAL::Exact_predicates_exact_constructions_kernel Kernel;
typedef CGAL::Polyhedron_3<Kernel>  Polyhedron_3;
typedef CGAL::Nef_polyhedron_3<Kernel> Nef_polyhedron_3;
typedef Nef_polyhedron_3::Point_3 Point_3;

int main()
{

  Point_3 a(1.0, 0.0, 0.0);
  Point_3 b(0.0, 1.0, 0.0);
  Point_3 c(0.0, 0.0, 1.0);
  Point_3 d(0.0, 0.0, 0.0);

  //Build a tetrahedron
  Polyhedron_3 P;
  P.make_tetrahedron(a,b,c,d);
  for  (Polyhedron_3::Vertex_iterator vi = P.vertices_begin(); vi != P.vertices_end(); ++vi)
  {
    std::cout <<"Point in Polyhedron: " << vi->point() <<std::endl;
  }

  std::cout << std::endl;

  Nef_polyhedron_3 NP(P);

  std::cout << "Iteration along face ...\n";
  int face_counter = 0;
  for(Nef_polyhedron_3::Halffacet_const_iterator f = NP.halffacets_begin (),
      end = NP.halffacets_end();
      f != end;
      ++f)
  {
    if(f->is_twin()) 
      continue;
    std::cout <<"########################################" << std::endl;
    std::cout << "Face number " << face_counter++  << std::endl; 
    for(Nef_polyhedron_3::Halffacet_cycle_const_iterator fc = f->facet_cycles_begin(),
	cycles_end = f->facet_cycles_end();
	fc != cycles_end;
	++fc)
    {
      int edge_counter = 0;
      if ( fc.is_shalfedge() )
      {
	std::cout <<"++++++++++++++++++++++++++++++++++++++++" << std::endl;
	std::cout << "Edge number " << edge_counter++  << std::endl; 
	Nef_polyhedron_3::SHalfedge_const_handle se = fc;
	Nef_polyhedron_3::SHalfedge_around_facet_const_circulator hc(se);
	Nef_polyhedron_3::SHalfedge_around_facet_const_circulator he(hc);
	std::cout <<"Edge consist of points: " << std::endl;
	CGAL_For_all(hc,he)
	{
	  Point_3  source_point(hc->source()->point());
	  Point_3  target_point(hc->target()->point());
	  std::cout <<"----------------------------------------" << std::endl;
	  std::cout <<"Source point " << source_point << std::endl;
	  std::cout <<"Target point " << target_point <<std::endl;
	}
      }
    }
  }
  return 0;
}