CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 05/31/2014 03:34 PM, Kobi Gurkan wrote:
> Hello,
>
> I'm trying to implement a limited 3D arrangement with multiple
> Nef_polyhedron_3.
> Before approaching it, I'm struggling with the concept of "shells",
> specifically on how to iterate on shells of a volume.
>  From what I understand, iterating using shells_begin() would give me
> each time a shell, which is, from the documentation:
> A |Shell_entry_iterator| is assignable to |SFace_handle|.
> But, I'm not dealing with SFaces at all - I want the regular Halffaces.
> Is there a better example for a case like mine or an explanation? I
> would really appreciate it.
>
> Thanks,
> Kobi
You can use the function

void    visit_shell_objects (SFace_const_handle f, Visitor &V) const

http://doc.cgal.org/latest/Nef_3/classCGAL_1_1Nef__polyhedron__3.html#a7a5e49319c66778abbf3cb6e702ca246

Visitor must provide:
      void visit(Halffacet_const_handle) {} //in you case this one 
should no be empty
      void visit(SFace_const_handle) {}
      void visit(Halfedge_const_handle) {}
      void visit(Vertex_const_handle) {}
      void visit(SHalfedge_const_handle) {}
      void visit(SHalfloop_const_handle) {}

You can also look at the implementation of the function
in the file CGAL/Nef_3/SNC_const_decorator.h.

Sebastien.