[vtkusers] wrong sub-extent processed by vtkImageConstantPad if combined with vtkDiscreteMarchingCubes and MPI

[Grothausmann, Roman Dr.]

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