[vtkusers] Proving a surface mesh of closeness

[Michael Jackson]

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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