[vtkusers] Disabling vtkImagePlaneWidget rotations?

[Daniel Kornhauser]

Hi:

I want my users to be able to *only* translate a vtkImagePlaneWidget , 
thus preventing them from rotating the plane with the mouse. How do I 
disable rotations? From the vtkImagePlaneWidget documentation it looks 
like it is possible:

    "In addition there are methods to constrain the plane so that it is 
aligned along the x-y-z axes."
       
from  http://www.vtk.org/doc/nightly/html/classvtkImagePlaneWidget.html

But I can't seem to find the methods to constrain a plane to be aligned 
:-(.  Or I just misunderstand the whole meaning of the quoted sentence 
above?

            Thanks

Daniel