[vtkusers] streaming vtkMarchingCubes?

[Bill Lorensen]

I looked at the vtk file and indeed it has multiple surfaces. How did
you generate this polydata? Can you tell me the pipeline you used?

On Sun, Jul 26, 2009 at 1:29 PM, Dominik Szczerba<dominik at itis.ethz.ch> 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)
> 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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>
>