CGAL users discussion list

[Martin Baeker <>]

YIKES!

That looks really evil, but I'll try it. My application is very
simple, so it may work.

Thanks a huge lot,

Martin.

> People who knows about Nef_polyhedron may be in vacation.
>
> In the meantime here is a DIRTY solution without any guarantee
> on the correctness of the structure after using it. Please use it with 
> caution (and do not expect any support if using it).
>
> This is  compiling on my machine:
>
> Nef_polyhedron nef;
> for (Nef_polyhedron::Vertex_const_iterator
>     it=nef.vertices_begin();it!=nef.vertices_end();++it)
> {
>  const Nef_polyhedron::Vertex* v=    &(*it);
>  Nef_polyhedron::Vertex* v_nc =const_cast<Nef_polyhedron::Vertex*>(v);
>  v_nc->point()=Point(0,0,0);
> }
>
> S.
>
> Martin Baeker wrote:
> > Dear all,
> >
> > this is my desperate third attempt to find someone who can help me
> > iterating over Vertices of a Nef_polyhedron in a non-const way (see below).
> >
> > Any light whatsoever shed on this will be most gratefully received.
> >
> > Pretty please??? <making Bambi eyes>
> >
> > Martin.
> >
> >
> >
> > Dear all,
> >
> > yesterday I asked about modifying a vertex of a Nef_polyhedron.
> >
> > By now I understand the following:
> > Obviously, I should use a
> > Nef_polyhedron::Vertex_iterator
> > insetad of a Nef_polyhedron::Vertex_const_iterator.
> >
> > The only problem I have is that this does not work because
> > the function vertices_begin()
> > seems to be const, so I cannot iterate my iterator.
> >
> > According to the manual, there should be a non-const version of this,
> > but I'm at a loss how to call it. I found that vertices_begin() is
> > defined in SNC_decorator.h and SNC_const_decorator.h, but *both* are
> > included in Nef_polyhedron_3.h Nef_polyhedron_3.h contains the follwoing 
> > declaration
> >
> > template <typename Kernel_, typename Items_ = typename 
> > CGAL::Default_items<Kernel_>::Items, typename Mark_ = bool>
> > class Nef_polyhedron_3 : public CGAL::Handle_for< 
> > Nef_polyhedron_3_rep<Kernel_, Items_, Mark_> >,
> >                            public 
> > SNC_const_decorator<SNC_structure<Kernel_,Items_,Mark_> >
> >
> > Is it this that is responsible for the choice? if so, how do I access
> > the non-const version of vertices_begin? Do I need to modify
> > Nef_polyhedron_3.h itself? That seems a "bit" dangerous to me...
> >
> > Any help would really be appreciated, since I'm completely lost...
> >
> > Martin.
> >
> >
> >
> >                    Priv.-Doz. Dr. Martin Bäker
> >                    Institut für Werkstoffe
> >                    Technische Universität Braunschweig
> >                    Langer Kamp 8
> >                    38106 Braunschweig
> >                    Germany
> >                    Tel.: 00-49-531-391-3073
> >                    Fax   00-49-531-391-3058
> >                    e-mail 
> > <>
> >
> > ---------- Forwarded message ----------
> > Date: Tue, 17 Aug 2010 10:18:53 +0200 (CEST)
> > From: Martin Baeker 
> > <>
> > To: CGAL Mailinglist 
> > <>
> > Subject: Modifying a vertex of a Nef_Polyhedron
> >
> > Dear all,
> >
> > I'm trying to loop over the vertices of a Nef_Polyhedron and modify
> > the coordinates of one of the vertices:
> >
> >       for(Nef_polyhedron::Vertex_const_iterator
> >           v = Cube.vertices_begin(),
> >           end = Cube.vertices_end();
> >             v != end; ++v)
> >         {
> >           if ( v->point() ==tip)
> >               v->point() = Nef_polyhedron::Point_3(0,0,0);//tip.x(), 
> > tip.y(), secondHeight);
> >                 break;
> >             }
> >
> > The trouble is that v seems to be const and cannot be modified, at
> > least that's how I understand the compiler error:
> >
> > error: passing ‘const CGAL::Point_3<CGAL::Cartesian<CGAL::Gmpq> >’ as 
> > ‘this’ argument of ‘CGAL::Point_3<CGAL::Cartesian<CGAL::Gmpq> >& 
> > CGAL::Point_3<CGAL::Cartesian<CGAL::Gmpq> >::operator=(const 
> > CGAL::Point_3<CGAL::Cartesian<CGAL::Gmpq> >&)’ discards qualifiers
> >
> > There seems to be no such thing as a non-constant Vertex-iterator - so
> > how can I loop over vertices in a way that I can modify their coordinates?
> >
> > Any help greatly appreciated, as usual,
> >
> > Martin.
> >
> > PS: Here's my bunch of Definitions, just in case:
> >
> > typedef CGAL::Cartesian<CGAL::Gmpq>   Kernel;
> > typedef CGAL::Polyhedron_3<Kernel>                           Polyhedron;
> > typedef CGAL::Nef_polyhedron_3<Kernel>  Nef_polyhedron;
> > typedef Kernel::Plane_3  Plane_3;
> > typedef Kernel::Ray_3  Ray_3;
> > typedef Kernel::Point_3    Point;
> > typedef Kernel::Segment_3    Segment;
> > typedef Kernel::Line_3    Line;
> > typedef Kernel::Vector_3  Vector_3;
> > typedef EKernel::Plane_3  EPlane_3;
> > typedef EKernel::Point_3    EPoint;
> > typedef EKernel::Vector_3  EVector_3;
> > typedef Polyhedron::Halfedge_handle 
> > Halfedge_handle;
> > typedef Polyhedron::Halfedge_around_facet_circulator 
> > Halfedge_facet_circulator;
> > typedef Polyhedron::Halfedge_iterator Halfedge_iterator;
> > typedef Polyhedron::Facet_handle                          Facet_handle;
> > typedef Polyhedron::Facet                          Facet;
> > typedef Polyhedron::Facet_iterator                   Facet_iterator;
> > typedef Kernel::Aff_transformation_3  Aff_transformation_3;
> > typedef Nef_polyhedron::Vertex_const_handle Vertex_const_handle;
> > typedef Nef_polyhedron::Halfedge_const_handle Halfedge_const_handle;
> > typedef Nef_polyhedron::Halffacet_const_handle Halffacet_const_handle;
> > typedef Nef_polyhedron::Volume_const_handle Volume_const_handle;
> > typedef Nef_polyhedron::Object_handle Object_handle;
> >
> >
> >                    Priv.-Doz. Dr. Martin Bäker
> >                    Institut für Werkstoffe
> >                    Technische Universität Braunschweig
> >                    Langer Kamp 8
> >                    38106 Braunschweig
> >                    Germany
> >                    Tel.: 00-49-531-391-3073
> >                    Fax   00-49-531-391-3058
> >                    e-mail 
> > <>
>
>
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                   Priv.-Doz. Dr. Martin Bäker
                   Institut für Werkstoffe
                   Technische Universität Braunschweig
                   Langer Kamp 8
                   38106 Braunschweig
                   Germany
                   Tel.: 00-49-531-391-3073
                   Fax   00-49-531-391-3058
                   e-mail 
<>