CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Sorry this is this that I posted in my first
mail + setting Infinity to -1 and UNDEFINED to -2
(that you are missing here).

S.


Asher Kamiraze wrote:
> Thank you Sebastien
>
> I finally did that and it seems to work:
>
>   Alpha_shape_2(Dt& dt, NT alpha = 0, Mode m = REGULARIZED)
>       :_alpha(alpha), _mode(m), 
>       use_vertex_cache(false), use_edge_cache(false)
>   {
>       Dt::swap(dt);
>       if (dimension() == 2)
>       {
>           // Compute the associated _interval_face_map
>           initialize_interval_face_map();
>
>           // Compute the associated _interval_edge_map
>           initialize_interval_edge_map();
>
>           // Compute the associated _interval_vertex_map
>           initialize_interval_vertex_map();
>
>           // merge the two maps
>           initialize_alpha_spectrum();
>       }
>   }
>
> Thank you for your help.
>
> Regards,
>
> Asher
>
> 2011/5/19 Sebastien Loriot (GeometryFactory) <sloriot.ml 
> <http://sloriot.ml>@gmail.com <http://gmail.com>>
>
>     Asher Kamiraze wrote:
>
>         OK. May this simple hack inspired from the 3D version will work?
>
>
>     That's what I did too.
>
>
>     S.
>
>
>          Alpha_shape_2(Dt& dt, NT alpha = 0, Mode m = REGULARIZED)
>            :_alpha(alpha), _mode(m),     use_vertex_cache(false),
>         use_facet_cache(false)
>            {
>              Dt::swap(dt);
>              if (dimension() == 2) initialize_alpha();
>            }
>
>         Regards,
>
>         Asher
>
>         2011/5/19 Mariette Yvinec 
> <
>         
> <mailto:>
>         
> <mailto:
>  
> <mailto:>>>
>
>
>            I see ...
>            In 3D you may construct  the Alpha_shape from the Triangulation
>            so that you can enter your vertices wih their info
>            in the triangulation and then build the Alpha_shape from the
>            triangulation.
>
>            In 2D, such a constructor does not seem to exist.
>            Obviously, we should add it.
>
>            Regards,
>            Mariette
>
>
>            Le 19/05/11 15:52, Asher Kamiraze a écrit :
>
>                Hi,
>
>                2011/5/19 Mariette Yvinec 
> <
>             
> <mailto:>
>                
> <mailto:
>             
> <mailto:>>>
>
>
>                    push_back should be private too.
>
>
>                Yes, that's what I thought.
>                
>                    If you use push_back,
>                     the triangulation will be updated but not the
>             alpha_shapes...
>
>                    I don't see any problem in what you propose.
>
>
>                Since I can use neither push_back nor insert, how can I
>             attach
>                info to a vertex?
>                If it is a triangulation, I add a point and get the returned
>                vertex, then attach the info on it. With alpha shapes, I
>             have to
>                give as input a range of points, and do not know how to
>             attach
>                info of the resulting vertices.
>
>                Regards,
>
>                Asher
>
>
>
>                    Le 19/05/11 12:46, Asher Kamiraze a écrit :
>
>                        Hi all,
>
>                        Is there a way to build an alpha_shape_2 with info?
>                        Something similar to a triangulation with info.
>                        I have also noticed that insert() is private in
>                        alpha_shape_2, but, push_back is not. Isn't it a
>             problem?
>
>                        Here is what I am trying to do:
>
>
>                           typedef
>                        CGAL::Exact_predicates_exact_constructions_kernel
>                                              K;
>
>                           struct vertex_info { Point point3d; };
>                           struct face_info {};
>
>                           typedef
>                      
>              CGAL::Triangulation_vertex_base_with_info_2<vertex_info,K>
>                                     Vb_2;
>                           typedef
>                      
>              CGAL::Constrained_triangulation_face_base_with_info_2<face_info,K>
>                             Fb_2;
>
>                           typedef CGAL::Alpha_shape_vertex_base_2<K,
>             Vb_2> Vb;
>                           typedef CGAL::Alpha_shape_face_base_2<K, Fb_2>
>              Fb;
>
>                           typedef
>             CGAL::Triangulation_data_structure_2<Vb,Fb>                
>                                TDS_2;
>                           typedef CGAL::Delaunay_triangulation_2<K  ,
>             TDS_2>                                         DT_2;
>
>                           typedef CGAL::Alpha_shape_2<DT_2> Alpha_shape_2;
>
>
>                                   Alpha_shape_2 alpha_shape(0.5);
>                                   // How to insert points in alpha_shape
>             with
>                        attached info?
>
>                        Hope you could help
>
>                        Best regards
>
>                        Asher
>
>
>                    --         Mariette Yvinec
>                    Geometrica project team
>                    INRIA  Sophia-Antipolis
>
>
>
>
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>
>
>            --     Mariette Yvinec
>            Geometrica project team
>            INRIA  Sophia-Antipolis  
>
>
>
>
>
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