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

[Bill Lorensen]

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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