CGAL users discussion list

[Juan Carlos Lopez Alfonso <>]

Hi Sebastien and Laurent:

Thank you for your answers and for your help, I am very thankful.

Only one question more if is possible. In the answer of Laurent about the off file, I am not sure what He is saying. Please could you explain with more detail, give me some code or reference about it?

Best regards and thank you again

Juan Carlos

On Fri, Nov 18, 2011 at 10:32 AM, Laurent Rineau (GeometryFactory) <> wrote:

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/

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