CGAL users discussion list

[Bo Zhou <>]

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
*/