CGAL users discussion list

[Efi Fogel <>]

The manual indicates that you should the other function (the one that accepts a halfedge).

Frankly, I would say that a 3rd function, which accepts a vertex, is due.

We may add it, but for now, again, it seems that you should be set.

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On Wed, Dec 23, 2015 at 2:08 PM, Mateus Bellomo <> wrote:

An extreme point of an edge e would be e->target() or e->source().

2015-12-23 4:37 GMT-02:00 Efi Fogel <>:

On Tue, Dec 22, 2015 at 9:33 PM, Mateus Bellomo <> wrote:

Hello,

I want to compute the visibility region of a point q inside a polygon (without holes) that is an Arrangement_2 face. I'm trying to use compute_visibility(q, f, out_arr) but I'm getting segmentation fault. The manual [1] says that q must be in the interior of face f and I'm using a point that belongs to an edge (in fact it is the extreme of an edge). It is considered a point to belongs an edge to be interior of a face?

No, of course not. The geometric embedding of an edge e is an open curve c, and the endpoints of the curve c are the geometric embeddings of the 2 vertices incident to the edge e. Similarly, the geometric embedding of a face f are the points in the interior of the face, and the curves on the boundary are the geometric embeddings of the edges incident to the face f.

I also noticed that is another compute_visibility(q, e, out_arr) where q belong to edge e. But I didn't understand what happens if q is an extreme point of e.

What is an extreme point of an edge?

Thanks in advance.

Mateus

[1] http://doc.cgal.org/latest/Visibility_2/classVisibility__2.html#a7d83efebd4f1b1ec86c3f0d07f47038b