CGAL users discussion list

[Andreas Fabri <>]

Hi Rob,

Note that the mesh simplification algorithm has the notion of
an EdgeCollapseSimplificationVisitor

http://www.cgal.org/Manual/3.4/doc_html/cgal_manual/Surface_mesh_simplification_ref/Concept_EdgeCollapseSimplificationVisitor.html#Cross_link_anchor_1340

This allows you to keep track of which edges get contracted.



In the example section of the User Manual
http://www.cgal.org/Manual/3.4/doc_html/cgal_manual/Surface_mesh_simplification/Chapter_main.html#Subsection_42.4.2

the second example entitled "Example Using an Enriched Polyhedron"
even shows how to use/implement such a visitor.

Best regards,

andreas


Rob wrote:
> Pierre,
>
>   Thank you very much for pointing me in this direction.  I've never
> used VTK before, and so hadn't thought to conduct that search.  I'd
> always assumed it was geared toward volume data, which is why I didn't
> think to look.  Upon further inspection, I stumbled across this thread
> (http://markmail.org/message/rgq35pb2p66x7nez).  Though this too is a
> bit outdated (from 2004), it seems to suggest that obtaining the actual
> progressive mesh information, rather than just the decimated mesh, might
> be difficult to do.  Either way, I'll look into VTK more to see how
> difficult obtaining the list of performed edge collapses might be.  If
> not, it seems that CGAL provides all the necessary Euler operations to
> perform the decimation myself, in which case I could maintain the
> necessary info on the edge collapses and vertex splits.  Would anyone
> else using CGAL be interested in an implementation of progressive meshes
> (if it turns out not to be patented by Microsoft)?
>
> Cheers,
> Rob
>
>
> Pierre JUILLARD wrote:
> > I see however that the publication is a little bit old...
> > VTK is now at version 5.2.1
> >
> >
> > Cheers,
> >
> > Pierre
> >
> >
> >
> > 2009/1/25 Pierre JUILLARD 
> > <>
> >
> >   
> > > Ok, so I come back with another suggestion.
> > >
> > > I had a look on the link you gave me and looked at the movies.
> > > It is actually a behaviour of ParaView which you may know (open source
> > > software base on VTK for scientific data visualization):
> > > http://www.paraview.org/
> > >
> > > I indeed noticed that when I was making a 3D mesh rotate, such
> > > simplifications were carried out (most probably to decrease the CPU load).
> > > As this software is based on VTK, I simply typped in Google: "vtk
> > > progressive mesh", and I found many results.
> > > You should tried.
> > >
> > > I most notably found this paper (Mesh Decimation Using VTK) which describe
> > > the classes in VTK allowing mesh decimation:
> > > http://www.cg.tuwien.ac.at/courses/Seminar/SS2002/Knapp_paper.pdf
> > >
> > > If you want to have a close look on these classes, I would recommend going
> > > to the doxygen documentation:
> > > http://www.vtk.org/doc/nightly/html/classes.html
> > >
> > > Regards,
> > >
> > > Pierre
> > >
> > >
> > > 2009/1/24 
> > > <>
> > >
> > > Pierre,
> > >     
> > > >  Thanks for the suggestion, but this is not really what I mean by the term
> > > > progressive mesh.  Rather, what I meant was the progressive mesh structure
> > > > introduced by Hoppe
> > > > (http://research.microsoft.com/en-us/um/people/hoppe/proj/pm).
> > > >  Basically, the
> > > > reason I asked on the CGAL discuss list is because it seems like CGAL
> > > > takes on
> > > > part of the way to implementing this structure.  Namely, they provide the
> > > > EdgeCollapsable mesh concept.  I was just curious how difficult it would
> > > > be to
> > > > implement and properly keep track of the edge collapses and to reintroduce
> > > > removed vertices with a vertex split.  I also wanted to see if anyone else
> > > > had
> > > > done this, as I  see no real use in re-inventing the wheel.
> > > >
> > > > Thanks,
> > > > Rob
> > > > --
> > > > You are currently subscribed to cgal-discuss.
> > > > To unsubscribe or access the archives, go to
> > > > https://lists-sop.inria.fr/wws/info/cgal-discuss
> > > >
> > > >       
> > >