[vtkusers] vtkImageData -> vtkVolumeMapper looks backwards

[powerhouseofexcellence]

Hi all,

I load 50 images into a vtkImageData object one at a time. When I hand
this image data object to one of the volume renderers, it seems my
slices are 'backwards', in that I loaded my first slice at position 0,
next slice at position 1, etc. But my slices come towards the viewer,
instead of marching away from the viewer, I guess this is because
VTK's z axis goes positive towards the viewer. I changed the spacing
of my image data object to be negative along the z axis to flip this
so it looks correct, but the render time is slowed down and is choppy
if I do that. Is there anyways to reconfigure the coordinate system or
do I manually have to load slice 0 into slot # 50 to get this to be
volume rendered in the 'right' order?

Thanks