CGAL users discussion list

["Jens K. Becker" <>]

Ah, you are right, this is exactly what happens. For some reason, with the
Homogeneous<Gmpz> there were never more than 2 facets of the same 
polyhedron in
the same plane (probably just pure luck). Now there are very often 3, 
sometimes
more in the same plane. Merging the first two facets works, merging the
resulting facet with the third does not work anymore.
There is a logical error in my code since I do not deal with this correctly.
Nice! Well, no, not nice, but at least I know now what to do.

Thanks very much, I will let you know if it works when I changed the code.

Jens Becker
--
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 Camille Wormser 
<>:

> > > CGAL error: precondition violation!
> > > Expr: circulator_size(h->vertex_begin()) >= size_type(3)
> > > while trying to remove a halfedge
> >
> > This means that you have degenerate faces, probably because some of  
> > the collapsing you did before was not acceptable, because the link  
> > condition was not satisfied.
>
>
> Sorry, I answered a bit too fast:
>
> In fact it means that there is a vertex with only 2 incident edges.  
> This can happen when you join facets (my link condition was not  
> relevant, since you do not maintain a triangulation), and it is  
> perfectly valid.
>
> The problem is that you cannot join two facets whose common boundary  
> consists in two or more consecutive edges: it would result in a  
> dangling edge.
>
> To deal with that, you should first remove this degree 2 vertex by  
> joining it with one of its two neighbors, check that these two  
> neighbors have degree greater than 2 (otherwise apply the same  
> treatment), and then you can merge the two facets.
> --
> Camille
>
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