CGAL users discussion list

["Jens K. Becker" <>]

Hi Bo,

The problem is not to add info to facets, cells or vertices, I can do
that. The problem is to decide which facet belongs to a polyhedron and
which is "just" a facet of a cell.

Jens 
On Sat, 2009-06-06 at 19:55 +0800, Bo Zhou wrote:
> Jens K. Becker wrote: 
> > Hi all,
> > 
> > I am puzzling over this problem for quite some time now and just cant
> > find a solution... I have a set of polyhedra that share facets and
> > vertices. Obviously, each facet can only belong to two polyhedra while a
> > vertex might belong to much more. If I want to delete a facet (or a
> > vertex) or add a facet (or a vertex) to one polyhedron, I have to add
> > the same to other polyhedra too. The most convenient would be to
> > construct a (Delaunay) triangulation of the part of the polyhedra where
> > things are going to happen, do whatever has to be done and reconstruct
> > the polyhedra from that triangulation. But how? The problem is the
> > reconstruction because I cannot think of any way how to decide which
> > facet of the triangulation belongs to which polyhedron. Is there an easy
> > way to do this? Or a hard way?
> > 
> > The triangulation would typically consist of 20-30 vertices only, I can
> > store which vertex belongs to which polyhedron in the vertices and/or I
> > could store which facet belongs to which polyhedron (before
> > inserting/deleting things from the triangulation) but I did not figure
> > out a way how to reconstruct it from this information. 
> > 
> > I tried to have a look at the example in CGAL3.4 that does remeshing of
> > a polyhedron, but did not really understand what is happening there (and
> > could not get it to compile neither, but that's another story). 
> > 
> > If anybody has any ideas, I would be very happy. He/she will be invited
> > for beers (wine, water you decide...) should we ever meet!
> > 
> > Thanks for any help,
> > 
> > Jens Becker
> > 
> >   
> Hello,
> I think maybe the meshes you need to deal with are like this one (from
> SIGGRAPH 2000 Course Notes Subdivision for Modeling and Animation) if
> I have not misunderstood the situation you illustrated.
> 
> To mark the facets to which mesh they belongs, maybe you can redefine
> some basic structure like the demo
> "examples/Polyhedron/polyhedron_prog_color.cpp" or in PDF manual page
> 1523, it redefined the half-edge structure to add a color component.
> 
> -- 
> /**
> * Bo Zhou
> * Blog : http://jedimaster.cnblogs.com
> * Mobile : +86 13451813691
> */
-- 
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