CGAL users discussion list

[Michael Jeulin-L <>]

Hi,

Sorry to disturb you, but I have a problem with the package Alpha Shape 2.
The triangulation is working fine, but I don`t succeed to extract the shapes
from Alpha_Shape. The number of shapes stay always at 0 whatever the value of
alpha.

So my soft never go into this loop :

for (Alpha_Shape_Edges_Iterator
edge_alpha_it=_alphaShape.alpha_shape_edges_begin();
edge_alpha_it!=_alphaShape.alpha_shape_edges_end(); edge_alpha_it++)
                a++;

Here is the CGAL  typedef that i use :

typedef CGAL::Triangulation_euclidean_traits_xy_3<K> Gt;
typedef CGAL::Delaunay_triangulation_2<Gt>  Delaunay;

typedef Delaunay::Vertex            Vertex;
typedef Delaunay::Face              Face;
typedef Delaunay::Face_handle       Face_handle;
typedef Delaunay::Point_iterator    Point_iterator;
typedef Delaunay::Vertex_circulator Vertex_circulator;
typedef Delaunay::Edge_iterator     Edge_iterator;
typedef std::pair<Face_handle,int>  Edge;
typedef Delaunay::Face_iterator     Face_iterator;


typedef CGAL::Alpha_shape_vertex_base_2<K>          Vb;
typedef CGAL::Alpha_shape_face_base_2<K>            Fb;
typedef CGAL::Triangulation_data_structure_2<Vb,Fb> Tds;
typedef CGAL::Delaunay_triangulation_2<K,Tds> Triangulation_2;
typedef CGAL::Alpha_shape_2<Triangulation_2>  Alpha_Shape;

//Alpha shape and the types
typedef Alpha_Shape::Face               Alpha_Face;
typedef Alpha_Shape::Vertex             Alpha_Vertex;
typedef Alpha_Shape::Edge               Alpha_Edge;
typedef Alpha_Shape::Face_handle        Alpha_Face_Handle;
typedef Alpha_Shape::Vertex_handle      Alpha_Vertex_Handle;
typedef Alpha_Shape::Face_circulator    Alpha_Face_Circulator;
typedef Alpha_Shape::Vertex_circulator  Alpha_Vertex_Circulator;
typedef Alpha_Shape::Locate_type        Alpha_Locate_Type;
typedef Alpha_Shape::Face_iterator      Alpha_Face_Iterator;
typedef Alpha_Shape::Vertex_iterator    Alpha_Vertex_Iterator;
typedef Alpha_Shape::Edge_iterator      Alpha_Edge_Iterator;
typedef Alpha_Shape::Edge_circulator    Alpha_Edge_Circulator;
typedef Alpha_Shape::Alpha_iterator     Alpha_Iterator;
typedef Alpha_Shape::Alpha_shape_edges_iterator Alpha_Shape_Edges_Iterator;

And here is my computation :

void XX::calculateShapes(double alpha)
{
    _alphaShape.set_alpha(alpha);
    _alphaShape.make_alpha_shape(_points2d.begin(), _points2d.end());

    //cout << "calculate shape with alpha " << alpha << endl;
    //cout << "Number Of alpha " << _alphaShape.number_of_alphas() << endl; 
}

I would be very grateful if someone have an idea of the problem and could help
me.

Regards.