[vtkusers] Spacing of vtkVolume

[Georg Ziegler]

Hello!

My pipeline looks like this
vtkImageImport -> vtkImageChangeInformation -> vtkVolume 
(+vtkVolumeRayCastMapper)

vtkImageChangeInformation is used to center the image data.

I load data with 256^3 pixels and spacing of (1.0, 1.0, 1.0)
and 128^3 pixels and spacing of (2.0, 2.0, 2.0)
and 64^3 pixels with spacing of (4.0, 4.0, 4.0)

I'm expecting these volumes to have the same size, but they don't.
The first volume is twice the size of the second and 4 times as large as 
the third.

It doesn't matter if I set the DataSpacing in vtkImageImport or 
OutputSpacing in vtkImageChangeInformation.
Does vtkVolume take the spacing into account at all?

What is the right way to get these volumes rendered at the same size?

Thanks,
Georg