CGAL users discussion list

["Jens K. Becker" <>]

Yes, they are for tetrahedrons. Thats where the infinite points come 
in. If you
give the triangulation a set of points in a plane, the triangulation algorithm
will automatically insert points so that it can make tetrahedrons.
Theoretically, they are "just somewhere in space", meaning very far away from
the points you give it. It then uses your points and these infinite points to
make tetrahedrons. This leaves you with a set of cells (each cell is a
tetrahedron) and one point of each cell is an infinite point. Get rid of these
and you have triangulated your plane. Thats how I do it.

Jens
--
Dr. J.K. Becker
University of Tuebingen - Institute for Geoscience
Sigwartst. 10 - 72076 Tuebingen (Germany)
Tel.: ++49 7071 29 73139   Fax: +49 7071 5059
web: http://www.jkbecker.de


Quoting Shi Yan 
<>:

> really? i thought the 3D triangulation is for tetrahedrons, not for
> triangles. i need definitely check the manual again.
>
> and i'm sorry, i don't quite understand what the infinite points are.
>
> thank you very much.
>
> On Thu, Oct 2, 2008 at 1:12 AM, Jens K. Becker 
> <>
>  wrote:
> > Hi Shi,
> >
> > I am not an expert with CGAL (yet), but I had the same problem. There are
> > plenty
> > of triangulation methods in 3D (all of them work in 3d if I am not
> > mistaken).
> > The resulting triangulation will be in 3D because infinite points will be
> > added
> > to your point set. If you just check for these points
> > (T.is_infinite(vertex))
> > and eliminating them should leave you with a triangulation in the plane.
> >
> > Greetings,
> >
> > Jens
> >
> > --
> > Dr. J.K. Becker
> > University of Tuebingen - Institute for Geoscience
> > Sigwartst. 10 - 72076 Tuebingen (Germany)
> > Tel.: ++49 7071 29 73139   Fax: +49 7071 5059
> > web: http://www.jkbecker.de
> >
> >
> > Quoting Shi Yan 
> > <>:
> >
> > > hello guys,
> > >
> > > i need to do triangulation inside a 3d triangle. the triangulation
> > > method provided by CGAL seems to be for 2D. so instead of me
> > > converting the 3D points into a 2D coordinate system, is there any
> > > convenient CGAL function that can do this for me?
> > >
> > > thank you very much.
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> >
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