CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

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:>>
>
>     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:>>
> >
> >         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