CGAL users discussion list

[Monique Teillaud <>]

Hi,

The symbolic perturbation is coded in Delaunay_triangulation_3.h, in 
class Perturbation_order. The side_of_sphere predicate uses this 
perturbation, so that it never returns 0.

Your question is interesting, but I don't see an easy way to mark 
tetrahedra on the fly, knowing the way the algorithm is coded...
As Laurent suggested, you can iterate on facets after the triangulation 
is constructed, call the non-perturbed predicate on their incident 
cells, and mark facets of tetrahedra that lie inside the polyhedral 
regions (using CGAL::Triangulation_cell_base_with_info_3).

Best,
        Monique Teillaud

Le 19/03/13 09:07, Philipp Blanke a écrit :
> Hello!
>
> I'd like to construct a Delaunay complex for a point set that contains
> several degenerate cases, i. e., >4 cospherical points. The doc says
> that the  Delaunay_triangulation_3 code solves the local disambiguity by
> using a perturbation scheme.
>
> If the tetrahedra that were constructed using this scheme would be
> marked, I could merge them in a preprocessing step to get a Delaunay
> complex consisting of convex polyhedra.
>
> Where in the code is the perturbation scheme used to select a possible
> tetrahedrization? I did not find this.
>
> Best regards,
> Philipp


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