CGAL users discussion list

["Laurent Rineau (GeometryFactory)" <>]

Le jeudi 17 novembre 2011 12:53:09 Juan Carlos Lopez Alfonso a écrit :
> Hi:
> 
> Well, I am following in details the examples and the documentation, but
> without lucky. I have used the input data of the examples in order to find
> more simplicity. My input set of points is "bunny_5000" and when I use the
> Alpha_Shape_3 class I dont see any desired results. Please see the
> following images:
> 
> http://dl.dropbox.com/u/2516160/bunny1.png
> http://dl.dropbox.com/u/2516160/bunny2.png
> 
> I have followed the first example in the charapter of Alpha_Shape_3 and for
> this reason my code is very simple.
> 
> http://dl.dropbox.com/u/2516160/code.txt

Let me quote your code:

> void Export2OFF(char * filedir, const Alpha_shape_3 &T, const
> std::map<Vertex_handle, int> &Vertices, const std::list<Cell_handle>
> &cells) {
> 
>         ofstream myfile (filedir);
>         if (myfile.is_open())
>         {
>               
>               myfile << "OFF" << "\n";
>               myfile << Vertices.size() << ' ' << cells.size() << ' ' << 0 
> << "\n";
>               
>               std::map<Vertex_handle, int>::const_iterator vit;
>               for (vit = Vertices.begin(); vit != Vertices.end(); vit++)
>               {
>               
>                       myfile << vit->first->point().x() << ' ' << 
> vit->first->point().y()
>                       << ' ' << vit->first->point().z() << "\n";>           
>   
>               }
>               
>               std::list<Cell_handle>::const_iterator itr;
>               for (itr = cells.begin(); itr != cells.end(); itr++)
>               {
>               
>                       Cell_handle cit = *itr;
>                       myfile << 4 << ' ' << 
> Vertices.find(cit->vertex(0))->second-1 << ' '
>                       << Vertices.find(cit->vertex(1))->second-1 << ' ' <<
>                       Vertices.find(cit->vertex(2))->second-1 << ' ' <<
>                       Vertices.find(cit->vertex(3))->second-1 << "\n";      
>           
>               }

The OFF format is for polygonal faces only. "4" does not mean that the lines 
is a tetrahedron. Here you put in the OFF file some non planar faces with 4 
vertices. I am not surprised that you OFF viewer display non-sense.

-- 
Laurent Rineau, PhD
R&D Engineer at GeometryFactory           http://www.geometryfactory.com/
Release Manager of the CGAL Project       http://www.cgal.org/