CGAL users discussion list

["Fernando Cacciola" <>]

Hi Qianqian,

The reason this doesn't just work is that border edges are not collapsed per-se 
but those non-border edges adjacent to the border vertices are, so the border 
vertices are moved.

One way to do what you need is via a placement policy wrapper whicch would 
return boost:::none for any edge adjacent to a border vertex.

Here's an example off the top of my head:

template<class GetPlacement_>
struct Placement_with_fixed_border_vertices : GetPlacement_
{
 typedef GetPlacement_ GetPlacement ;

 typedef typename GetPlacement::Profile Profile ;

 typedef typename GetPlacement::result_type result_type ;

 result_type operator()( Profile const& aProfile ) const
 {
    if ( is_border_vertex(aProfile.v0()) || is_border_vertex(aProfile.v1()) )
          return boost::none ;
    else
         return this->GetPlacement::operator()(aProfile);
 }

  bool is_border_vertex( typename Profile::const_vertex_descriptor v )
  {
     // whatever works for you enriched polyhedron, i.e.: true if any adjacent 
halfedge is a border.
  }
} ;


HTH

Fernando Cacciola
GeometryFactory