CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Costas Tsirogiannis wrote:
>  I have not defined a copy constructor for the augmented half-edges, 
> would that change something here?
So no, the default should be fine.

> On Tue, Jul 6, 2010 at 3:31 PM, Sebastien Loriot (GeometryFactory) 
> <sloriot.ml <http://sloriot.ml>@gmail.com <http://gmail.com>> wrote:
>
>     Did you define a copy constructor and forget to copy the object?
>     I think in your case, you should use a boost::Variant as the number of
>     possible types is only 2.
>
>
>
>     Costas Tsirogiannis wrote:
>
>
>         Here's scraps of code that are indicative of the situation:
>
>         * In the augmented halfedge class I store a CGAL::Object that
>         contains
>         * a handle, it could be either a face handle or an edge stored
>         in it:
>
>         Object  _corresponding_triangulation_object;
>
>         * And the member functions that make use of it are:
>
>          bool overlaps_with_triangulation_edge(void)
>          { bool temp = _corresponding_triangulation_object.template
>         is<Triangulation_face_handle>();
>           return !temp; }
>          void set_corresponding_triangulation_object( Object &obj )
>          { _corresponding_triangulation_object = obj; }
>
>          template< typename Triangulation_item >
>          void set_corresponding_triangulation_object( Triangulation_item
>         &t_item )
>          { _corresponding_triangulation_object =
>         Construct_object()(t_item); }
>
>          Object& corresponding_triangulation_object(void)
>          { return _corresponding_triangulation_object; }  
>
>         * So let's say that at some point some function "A"  is called
>         where it does this:
>
>         Halfedge_handle current_ph;
>
>         **** do something with current_ph ****
>
>          Halfedge_handle   target_ph, old_ph;
>
>         target_ph = fnwk.surface_polyhedron().split_edge( current_ph );
>         target_ph->vertex()->point() = p;
>
>          old_ph = target_ph->next();
>          
> target_ph->set_corresponding_triangulation_object(current_ph->corresponding_triangulation_object());
>                  
>          CGAL_assertion(target_ph->overlaps_with_triangulation_edge());
>          
> target_ph->opposite()->set_corresponding_triangulation_object(current_ph->opposite()->corresponding_triangulation_object());
>          
> CGAL_assertion(target_ph->opposite()->overlaps_with_triangulation_edge());
>          
> old_ph->opposite()->set_corresponding_triangulation_object(current_ph->opposite()->corresponding_triangulation_object());
>
>         * Up to here everything is executed ok. But in the following
>         code, after the execution
>         *of "A" is done, when I traverse the polyhedron face that
>         contains the above halfedges I get *segmentation faults  either
>         in the std::cout line or in the line where
>         *->overlaps_with_triangulation_edge() is called.
>
>
>         Halfedge_handle other_ph = ..... ;
>         Triangulation_edge entry_te = ..... ;
>         Triangulation_edge current_te = entry_te;
>
>         while( !(other_ph->overlaps_with_triangulation_edge()) ||
>         current_te == entry_te )
>          {
>             std::cout << " other_ph->vertex : "<<
>          other_ph->vertex()->point() << std::endl;
>
>            other_ph = other_ph->next();
>
>            if(other_ph->overlaps_with_triangulation_edge())
>              CGAL::assign(current_te,
>         other_ph->corresponding_triangulation_object() );
>          }
>
>          I think there is no problem with accessing the vertex point,
>         the memory error
>         has to do with the triangulation handles stored as objects in
>         the halfedges.
>
>         thanks
>
>         Constantinos
>
>
>
>
>         On Tue, Jul 6, 2010 at 7:48 AM, Sebastien Loriot
>         (GeometryFactory) <sloriot.ml <http://sloriot.ml>
>         <http://sloriot.ml>@gmail.com <http://gmail.com>
>         <http://gmail.com>> wrote:
>
>            Costas Tsirogiannis wrote:
>
>                Greetings,
>
>                I have a problem with run-time errors coming from an
>         unorthodox
>                use of handles:
>
>                 I make use of a triangulation and of an augmented
>         polyhedron_3
>                object. This augmented polyhedron
>                is a refinement of the surface represented by the
>         triangulation
>                : as some algorithm goes on, new edges
>                are added on what used to be the triangular faces. It is
>                important that the halfedges,faces and vertices
>                on the polyhedron that originate from features of the
>                triangulation should point to the corresponding triangulation
>                features.  Thus each feature stores a handle of the original
>                triangulation object: a polyhedron vertex stores a handle
>                to the original triangulation vertex of the same
>         coordinates, a
>                halfedge stores a handle to the triangulation edge or
>                face on which it lies etc.
>                 When a feature is refined eg a halfedge is split, these
>         stored
>                handles of triangulation features are copied to
>                the newly created features. And then segmentation faults
>         appear.
>
>            What do you use to split halfedges ? (the underlying question
>         being how
>            your handles are set)
>
>
>                Specifically, things go wrong when there is an attempt
>                to access the handle member object of the new feature
>         outside of
>                the function that created the feature (and copied the
>                handle object to it).  Any ideas for what could fix this?
>
>                thanks
>
>                Constantinos
>
>
>
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