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

[Grothausmann, Roman Dr.]

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