[vtkusers] streaming vtkMarchingCubes?

[Dominik Szczerba]

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)
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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