CGAL users discussion list

[Laurent Rineau <>]

Thomas, your code was quite difficult to understand. You cannot assume us to 
even try. Nevertheless, it was challenging, and I tried.

I understand that, given a facet 'f', and an edge of that facet, you want to 
turn around the edge, avoiding infinite facets, and 'f' itself.

Your mistake is the following test:
>        if ((fCirc->first == f.first) && (fCirc->second == f.second)) {
>          continue;

It is possible that fCirc is not equal to f, but is equal to      
t_.mirror_facet (f). It depends of the orientation of the circulator around 
the edge.

To correct that test, you can turn it into:

  if(*fCirc == f || *fCirc == f_mirror)
    continue;

given that you can put the following before the 'for' loop:

  const Facet f_mirror = t_.mirror_facet(f);



You can also use a different form of the incident_facets function:

     Rt_Facet_circulator fCirc = t_->incident_facets(f.first,
                                                     vertices[i%3],
                                                     vertices[(i+1) % 3],
                                                     f);
     Rt_Facet_circulator fCircEnd = fCirc;
     // here *fCirc == f
     ++fCirc;
     // here *fCirc is the facet just after f
     faceCounter = 0;

     // the following test should be useless 
     // if t_.dimension()==3
     if( fCirc != fCircEnd)
       do {
          // [...]
     }

That way, you control the initialization of the Tr::FacetCirculator, and you 
can be sure that fCirc will never be equal to f or to its mirror in the 
do/while loop.

-- 
Laurent Rineau
INRIA - Sophia Antipolis
BP 93, 2004 Route des Lucioles
06902 Sophia Antipolis Cedex FRANCE
Tel: +33 4 92 38 78 62 (Fax: +33.4.97.15.53.95)