[vtkusers] Proving a surface mesh of closeness

[Dominik Szczerba]

That can be true accidently for an arbitrary mesh.

Dominik

On Friday 03 October 2008 07:52:05 pm Michael Jackson wrote:
> T=2V-4
>
> Where T is the number of triagles and V is the number of vertices.
> Something about Euler's Polyhedra equation...
>
>
> Mike
>
> On Oct 3, 2008, at 1:14 PM, Marie-Gabrielle Vallet wrote:
> > I think there is a easier way of checking the surface closeness. I
> > mean using vtk facilities, instead of writing a (yet another) new
> > algorithm.
> >
> > VTK library has algorithms to extract a mesh boundary, i.e. the set
> > of faces (in 3D) or edges (in 2D) that are not shared by two cells.
> > See vtkFeatureEdges. The mesh is close if and only if this set is
> > empty. If it not, you can visualize the holes that must still be
> > closed.
> >
> > Pamela is trying to do the same thing today. Have a look at the
> > thread "get boundary triangles from a mesh" on this mailing list.
> >
> > By the way, Charles, are you sure you are not re-inventing the wheel ?
> >
> > Marie-Gabrielle
> >
> > >  Date: Fri, 3 Oct 2008 08:17:31 +0200
> > >  From: Dominik Szczerba <dominik at itis.ethz.ch>
> > >  Subject: Re: [vtkusers] Proving a surface mesh of closeness
> > >  To: vtkusers at vtk.org
> > >  Message-ID: <200810030817.31796.dominik at itis.ethz.ch>
> > >  Content-Type: text/plain;  charset="utf-8"
> > >
> > >  If it is manifold then pick the 1st element and make sure each
> >
> > one it has the
> >
> > >  proper number of neighbors (for triangles: 3). Mark the element
> >
> > as 'visited'
> >
> > >  and visit all his neighbors, repeating the procedure. At the end,
> >
> > if number
> >
> > >  of visited elements equals to number of elements in the mesh and
> >
> > all have
> >
> > >  their expected neighbors the mesh is closed.
> > >
> > >  DS
> > >
> > >  On Friday 03 October 2008 02:48:59 am Charles Monty Burns wrote:
> > >  > Hello,
> > >  >
> > >  > I repaired a surface mesh and want to prove whether the mesh is
> >
> > totally
> >
> > >  > closed or not. Save is save ...
> > >  >
> > >  > How can I do this?
> > >  >
> > >  > Greetings
> > >
> > >  --
> > >  Dominik Szczerba, Ph.D.
> > >  Computational Physics Group
> > >  Foundation for Research on Information Technologies in Society
> > >  http://www.itis.ethz.ch
> >
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-- 
Dominik Szczerba, Ph.D.
Computational Physics Group
Foundation for Research on Information Technologies in Society
http://www.itis.ethz.ch