CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 03/23/2012 03:26 PM, Juan Carlos Lopez Alfonso wrote:
> Hi,
>
> Thank you for your answer. But about this, I can't remove points, I am
> looking for a Triangulation function to remove tetrahedrons. Is there
> any form to do that?
If you can't remove point, then I don't see any solution.
You can't simply say remove a tetrahedron from a triangulation, because
you would have a "void" (this is not specific to CGAL).
You said you can't mark tetrahedra as exterior so I think there is no 
solution to your problem.

If you don't restrict yourself to Delaunay you might make some
face flipping operations but it's a bit tricky (and I am not sure
it will solve your small edge problem).

Sebastien.


> Regards
> Juan Carlos
>
> On Thu, Mar 22, 2012 at 10:54 PM, Sebastien Loriot (GeometryFactory)
> <>
>   wrote:
> > On 03/21/2012 05:04 PM, Juan Carlos Lopez Alfonso wrote:
> > > Hi,
> > > thank you for your answer, but this solution don't solve my problem,
> > > because I need to iterate the set of tetrahedrons which are incident
> > > in the infinite vertex. Some thing like this:
> > >
> > > T.incident_cells(T.infinite_vertex(), std::back_inserter(infinite_cells));
> > >
> > > and for this reason I need to eliminate some of them of the
> > > triangulation in order to have other external tetrahedrons.
> > >
> > > any other idea?
> >
> > Maybe removing one on the two points that are too close from the
> > triangulation?
> >
> > Sebastien
> >
> > > Best Regards
> > > Juan Carlos
> > >
> > > On Wed, Mar 21, 2012 at 4:51 PM, Mariette Yvinec
> > > <>
> > >     wrote:
> > > > One way to do it
> > > > is  to instantiate the triangulation with
> > > > a base cell class of type Triangulation_cell_base_with_info_3
> > > > that supports additionnal information stored in the triangulation cells.
> > > > Then you may add a boolean in each cell
> > > > to mark tetrahedra inside/outside the domain of interest.
> > > >
> > > >
> > > > Le 21/03/12 12:32, Juan Carlos Lopez Alfonso a écrit :
> > > >
> > > > Hi all,
> > > >
> > > > I have a question related with a delaunay triangulation. I have
> > > > triangulated a set of points and I want to know how I can remove some
> > > > tetrahedrons of this triangulation.
> > > >
> > > > For example I have the following triangulation: Delaunay T;
> > > > and I have iterated over all tetrahedrons and when one edge of one of
> > > > them is more than a defined threshold, I want to eliminate this
> > > > tetraheron of T. The idea is eliminate external tetrahedrons in order
> > > > to obtain a nonconvex domain triangulation. I need eliminate this
> > > > tetrahedrons of T, because I need to iterate the set of tetrahedrons
> > > > which are incident in the infinite vertex. Some thing like this:
> > > >
> > > > T.incident_cells(T.infinite_vertex(),
> > > > std::back_inserter(infinite_cells));
> > > >
> > > > Is there any form to eliminate tetrahedrons of T?
> > > >
> > > > Best regards
> > > > Juan Carlos
> > > >
> > > >
> > > > --
> > > > Mariette Yvinec
> > > > Geometrica project team
> > > > INRIA  Sophia-Antipolis
> >
> >
> > --
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