[vtkusers] scaling a volume

[Melanie Tory]

Hi all,

I am creating a subvolume using vtkImageReslice, and I want to volume
render the subvolume and magnify it in size relative to other objects in
the scene. I create a vtkVolume using the subvolume data and render it
using ray-casting.  (I have the opacities all set to 1 and the colours set
to the original image colours, so that each side of the subvolume object
just shows an image at that position in the original volume.)  
This all works fine. However, when I try to enlarge my vtkVolume using

volume->SetScale(2.0)

I get a weird effect.  The image appears to get magnified by 2, but the
volume object itself only gets enlarged a little bit.  The effect is that
the magnified image only contains part of the original image, as though it
were zoomed instead of made larger.

Any idea what I'm doing wrong?  I'd appreciate your help.

Thanks,
Melanie Tory
Simon Fraser University