[vtkusers] vtkDiscreteMarchingCubes and vtkMarchingCubes do not handle sub-extents correctly

[Bill Lorensen]

Roman,

I think that only algorithms that implement ThreadedExecute() will
properly work in your situation. vtkMarchingCubes and
vtkDiscreteMarchingCubes do not implement that method.

I suggest using vtkContourFilter instead of vtkMarchingCubes. There is
no equivalent for vtkDiscreteMarchingCubes.

Perhaps in the future I can look at DiscreteMarchingCubes.

Bill

On Wed, Nov 25, 2015 at 1:53 PM, Bill Lorensen <bill.lorensen at gmail.com> wrote:
> Roman,
>
> With your sample programs and my data, I can reproduce the bad results
> for Marching and DiscreteCubes. (without ImagePad - that is another
> issue).
>
> Now to find the bugs....
>
> Bill
>
> On Wed, Nov 25, 2015 at 11:27 AM, Bill Lorensen <bill.lorensen at gmail.com> wrote:
>> Looks like a bug. I'll take a look.
>>
>>
>> On Wed, Nov 25, 2015 at 9:04 AM, Grothausmann, Roman Dr.
>> <grothausmann.roman at mh-hannover.de> wrote:
>>> I just noticed that vtkDiscreteMarchingCubes and also vtkMarchingCubes do
>>> not handle sub-extents correctly. It seems both filters do not handle the
>>> translation of each sub-extent. If the result is saved in a PVTP-file and
>>> opened in ParaView, the content of each VTP-file is placed over the others.
>>> In contrast vtkContourFilter does handle the translation of each sub-extent
>>> correctly, the content of each VTP-file is positioned correctly, see e.g.
>>> https://github.com/romangrothausmann/VTK-CLIs/blob/9eac8644101360d18f2ff70928d457aabddbbbf0/marching-cubes_MPI.cxx
>>>
>>> On 24/11/15 14:26, Grothausmann, Roman Dr. wrote:
>>>>
>>>> Dear mailing list members,
>>>>
>>>>
>>>> Trying to cap the output of vtkDiscreteMarchingCubes by applying
>>>> vtkImageConstantPad on the input before does not work if running
>>>> vtkStreamingDemandDrivenPipeline by e.g. a vtkMPIController.
>>>>
>>>> If I run this program with the parameter for capping, i.e. employing
>>>> vtkImageConstantPad:
>>>>
>>>> https://github.com/romangrothausmann/VTK-CLIs/blob/9eac8644101360d18f2ff70928d457aabddbbbf0/discrete_marching-cubes_MPI.cxx#L90
>>>>
>>>>
>>>> I get an error such as:
>>>> vtkImageData (0x1868190): GetScalarPointer: Pixel (0, 0, 341) not in
>>>> memory.
>>>>   Current extent= (249, 499, 0, 479, 0, 429)
>>>>
>>>> It seems that vtkImageConstantPad processes the wrong sub-extent. Would
>>>> that be
>>>> a filter internal problem or of my code?
>>>>
>>>> Could the problem be related to the fact that I try to combine structured
>>>> extent
>>>> (Index (IJK) based, not using ghost levels) with piece-based extent that
>>>> uses
>>>> ghost levels?
>>>>
>>>> The problem even occurs when the extent is not extended at all.
>>>> The program works as expected if vtkImageConstantPad is avoided.
>>>>
>>>> Any help or hints are very much appreciated
>>>> Roman
>>>>
>>>
>>> --
>>> Dr. Roman Grothausmann
>>>
>>> Tomographie und Digitale Bildverarbeitung
>>> Tomography and Digital Image Analysis
>>>
>>> Institut für Funktionelle und Angewandte Anatomie, OE 4120
>>> Medizinische Hochschule Hannover
>>> Carl-Neuberg-Str. 1
>>> D-30625 Hannover
>>>
>>> Tel. +49 511 532-2900
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>>
>>
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>
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