CGAL users discussion list

[Monique Teillaud <>]

Hi,

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* Each facet p,q,r of the convex hull is
- the finite facet of an infinite cell p,q,r,inf
- one of the facets of a finite cell p,q,r,s
These two cells must be neighbors in the data structure.
You must be very careful with orientation (see Sec 39.1)

* When two facets p,q,r and p,q,s of the convex hull share a common edge 
p,q, then their respective infinite cells p,q,r,inf and p,q,s,inf are 
neighbors through a common facet p,q,inf.
Here again, be careful with orientation.


In fact, it is easier (and safer) to just read the vertices of your 
external triangulation, and construct a CGAL triangulation from scratch 
by inserting the corresponding points...

Best,
        Monique Teillaud

Le 18/07/12 17:56, Simon Perkins a écrit :
> Hello
>
> I'm writing a loader that will read information from an external file
> format into the CGAL Triangulation_3 data structure. One thing that may
> be problematic is that the file format doesn't explicitly define the
> infinite cells intrinsic to CGAL's representation and so I will have to
> create them myself. I don't find this too daunting but I'm not sure how
> the neighbours of an infinite cell should be configured. It seems clear
> to me that the one can set the neighbour of the infinite vertex to be
> the finite cell sharing a facet with the infinite cell, but I'm not sure
> how to handle the neighbours of the other three vertices on the facet
> itself.
>
> Would it be valid to set them to a random finite cell for example?
>
> kind regards
>    Simon


--
Monique Teillaud
INRIA Sophia Antipolis - Méditerranée
http://www.inria.fr/sophia/members/Monique.Teillaud/