[vtkusers] Is there a way to limit movement of vtkCamera to a plane?

[Mike Gagnon]

Hello!

I'm setting up 4 views on a vtkActor - 3 of which are views along the X 
Y Z axis respectively.  Is there a way to limit the allowed motion of 
the camera, so that all it can do is zoom in and out, for a given renderer?

Thanks!
Mike