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

[Bill Lorensen]

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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