[vtkusers] mis-registered volume and extracted surfaces.

[Dongbai Guo]

I am trying to overlay the extracted surfaces on top of the volume.
Without applying any transformation. If I limited the image extent
with a vtkExtractVOI filter. The result surface and volume will
be mis-aligned, looks like it is the volume that is no longer centered
at origin, but rather the volume center.  Yet the bounds I get (using
GetBounds function) for  all volume/surfaces are extractly the same.
And the outline I get for the volume is also centered at origin.

I am using TIFFReader to read volume slices and this is
vtk4.2 running on Linux (Redhat Fedora).

Is this a bug or an expected behavior?

thank you.

dongbai