[vtkusers] streaming vtkMarchingCubes?

[Dominik Szczerba]

On Sun, 2009-07-26 at 19:29 +0200, Dominik Szczerba wrote:
> On Sun, 2009-07-26 at 12:35 -0400, Bill Lorensen wrote:
> > I am surprised at this. vtkMarchingCubes should produce manifold and
> > oriented surfaces. There should be no duplicate points.
> > vtkMarchingCubes can produce multiple, topologically disconnected
> > surfaces. vtkDiscreteMarchingCubes can (and should) produce
> > geometrically continuous but topologically disconnected surafces.
> > 
> > Can you provide a test dataset that reproduces the problem?
> > 
> 
> I hanged a small sample on:
> 
> http://otoro.itis.ethz.ch/~dominik/tmp/test.vtk
> 
> I got this while segmenting a smooth scalar field on a (Windows virtual)

not segmenting but running vtkMarchingCubes on a smooth scalar field -
sorry. -- Dominik

> machine with very little memory. I do not get this on a (linux real)
> machine with lots of memory.
> 
> Running connectivity filter you will notice a few disconnected regions.
> It goes away after merging coincident points (and the number of points
> is reduced indicating degenerate original points).
> 
> I just need to get a warning when the output is in such condition to not
> have to merge points by default, which degrades performance.
> 
> -- Dominik
> 
> > Bill
> > 
> > On Sun, Jul 26, 2009 at 8:27 AM, Dominik Szczerba<dominik at itis.ethz.ch> wrote:
> > > I have experimentally found out that vtkMarchingCubes can generate
> > > geometrically continuous but topologically disconnected isosurfaces,
> > > i.e. the isosurface is cut into stripes along one axis with duplicate
> > > points on the edges. How do I get a control of this behavior,
> > > especially, to know if there will be disconnected stripes so I should
> > > merge the points (I need topological consistency)?
> > >
> > > -- Dominik
> > >
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