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Re: [cgal-discuss] facet iterator


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  • From: Manuel Caroli <>
  • To:
  • Subject: Re: [cgal-discuss] facet iterator
  • Date: Thu, 13 Aug 2009 18:33:04 +0200

Dear Michal,

I suggest you have a more in-depth look at the documentation of the 3D triangulation package and the 3D triangulation data structure package.
I will try to give you some short hints, but I cannot repeat the whole documentation.


wrote:
Hi,
I have a question. What does it means facet in 3D triangulation? For
Facets are the 2-simplices (triangles) that are contained in the triangulation.
example, consider the cell (a,b,c,d) of the triangulation. Contains the
triangluation following facets only? :
If you are talking of a triangulation of the points a, b, c, and d yes. But there are also infinite facets (see documentation). Note that facets are only represented implicitly, i.e. as a Cell_handle and an index (see documentation).

a,b,c
a,b,d
a,d,c
b,d,c


Or are there two facets for each side of each triangle? :
I don't understand this.

a,b,c
c,b,a
a,b,d
b,b,a
a,d,c
c,d,a
b,d,c
c,d,d


Which kind will give me following code? :
It iterates through all the facets of the triangulation visiting each facet exactly once. (see doc).

for (Dh::Facet_iterator it = T.facets_begin(); it != T.facets_end(); ++it)
{
};


I have another question too. How can I determine incident cells of the
facet denoted by thee vertex handels?
If you are given three vertices you can use the function is_facet to get one of the cells it is incident to. You can get the other cell using the neighboring relation.

best

Manuel



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