CGAL users discussion list

[Asher Kamiraze <>]

OK. May this simple hack inspired from the 3D version will work?

  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 <>

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 <>

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