CGAL users discussion list

[Monique Teillaud <>]

Well, in both cases (finite or infinite vertex), the circulator goes 
ccw, seen from the vertex.

In the case of the infinite vertex, think of the triangulation as if it 
were on a sphere, with the infinite vertex as the pole. The infinite 
vertex sees its incident vertices traversed in ccw order by the 
circulator. But if you look from the interior of the convex hull, then 
you see the vertices of the convex hull traversed in cw order by the 
circulator.

--
Monique Teillaud
http://www.inria.fr/sophia/members/Monique.Teillaud/
INRIA Sophia Antipolis - Méditerranée
Institut National de Recherche en Informatique et Automatique

Le 21/06/13 07:45, Sebastien Loriot (GeometryFactory) a écrit :
> It is not documented but if you are at the infinite vertex it will be
> cw, and ccw otherwise.
>
> Sebastien.
>
> On 06/20/2013 06:24 PM, Raul Gallegos wrote:
> > Hello,
> >
> > I am getting the voronoi cell (a Polygon_2) from a Vertex_handle, on a
> > constrained Delaunay Triangulation.
> >
> > Getting the points of the Polygon is easy when all the faces aren't
> > constrained (blind), because you only use a Circulator to get all the
> > faces incident to the Vertex_handle and get their circumcenters.
> >
> > When there is Constrained it becomes a pain, because you need to
> > calculate the points of that polygon that intersect with the constraint.
> >
> > I got this points by using the middle point of the current Vertex_handle
> > comparing it with the vertex_handle on the current face of the
> > circulator, and it works, I get the points.
> >
> > I have a problem understanding which is the order of a circulator, is it
> > cw? ccw?, because to get a Polygon_2 I have to get the points in order,
> > if not it becomes a totally different Polygon.
> >
> > Can someone help me with this? first let me understand which is the
> > order of a Circulator (for 2D meshes) and maybe if there is an easier
> > way to get the voronoi cell from a Vertex_handle for Constrained
> > Delaunay Triangulations.
> >
> > Thank you.
> > --
> > Raul O. Gallegos Hidalgo