CGAL users discussion list

[Laurent Rineau <>]

On Tuesday 24 June 2008 16:48:08 Hui Ding wrote:
> Thanx, but what do you mean about "first" "second" of Facet f?? you mean:
> f ->vertex(( (f+1)+1 )&3)f ->vertex(( (f+1)+2 )&3)f ->vertex(( (f+1)+3
> )&3)??

Have you ever read parts of the documentation of CGAL 3D Triangulations?!

If Tr is a 3D triangulation, "Tr::Facet" is the 
type "std::pair<Cell_handle,int>".

On Tuesday 24 June 2008 17:15:08 Hui Ding wrote:
> Well, because when I try to do something like this:
>
>   std::ofstream oFile("output",std::ios::out);
>   for(Facet_iterator fit =
> c2t3.facets_begin();fit!=c2t3.facets_end();fit++){ oFile<<
> fit.first->vertex((fit.second+1)&3)->Point();
>      oFile<< fit.first->vertex((fit.second+2)&3)->Point();
>      oFile<< fit.first->vertex((fit.second+3)&3)->Point();
>   }
>
> it comes the errors:
> error C2227: left of '->Point' must point to class/struct/union/generic
> type error C2039: 'first' : is not a member of 'CGAL::Filter_iterator<I,P>'
> etc.

Here you assume, incorrectly, that Face_iterator is the same type (or at 
least 
has the same API) as Facet. And you misspelled "point()" as "Point()"!

Use the following:

  for(Facet_iterator fit = c2t3.facets_begin();fit!=c2t3.facets_end();fit++){
      oFile<< fit->first->vertex((fit->second+1)&3)->point();
      oFile<< fit->first->vertex((fit->second+2)&3)->point();
      oFile<< fit->first->vertex((fit->second+3)&3)->point();
   }

You can use a code a bit more clear:

  typedef Tr::Cell_handle Cell_handle;

  for(Facet_iterator fit = c2t3.facets_begin();fit!=c2t3.facets_end();++fit)
  {
      const Cell_handle& ch = fit->first;
      const int facet_index = fit->second;
      oFile<< ch->vertex((facet_index+1)&3)->point();
      oFile<< ch->vertex((facet_index+2)&3)->point();
      oFile<< ch->vertex((facet_index+3)&3)->point();
   }

I hope that will give you the will to read some parts of the documentation.

-- 
Laurent Rineau, PhD
Engineer at GeometryFactory
http://www.geometryfactory.com/