[vtkusers] vtkImageAppend Runtime Error

Siavash Khallaghi siavashk at ece.ubc.ca
Thu Sep 17 15:24:51 EDT 2015

After a lot of debugging, I found the culprit. It has nothing to do with
vtkImageAppend, but the inputs that I was supplying to the filter.
Basically, overlapImage has bad memory sometimes (I don't know why).

overlapImage is the output of a vtkExtractVOI filter and has
mapper->GetInput() as input data. I was writing it out after the update
call, and everything worked fine, so I did not suspect it.

After the vtkExtractVOI update call, I set the the extent of the
overlapImage to be between (0, 0, 0) and (Nx, Ny, Nz), where is N is the
number of pixels in each dimension. This is because I do calculations with
the assumption that the extent starts from (0, 0, 0). Now something really
weird happens:

I noticed that after overlapImage->SetExtent(0, Nx, 0, Ny, 0, Nz), I can no
longer write out the overlapImage. If I write it out, it would be empty
(size of 0 KB). So when I was passing it to vtkImageAppend, it would also
crash my program.

Here is an example set of numbers for the extent:

overlapImage extent before SetExtent: 501, 1910, 251, 1007, 0, 0
overlapImage extent after SetExtent: 0, 1410, 0, 757, 0, 0

Does anyone know why setting the image extent manually would mess up the
memory for vtkImageData? Maybe SetExtent is not meant to be used in this

In the mean time, I will work on creating a small program that would
reproducible the problem.

Thank you,


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