[vtkusers] World coordinates of the vtkRenderWindows screen boundaries

[Sarah Macumber]

Hello all, 
 
I am looking for a way to determine the camera's viewable extents in world coordinates, which I need to know to buffer data.
 
I cannot view all my data at once, so it is broken up into sections along the axis.  I place some data at (0,0) and then pan / zoom around and would like to know what new range of data I am now looking at in the event that I may need to load some more data into my buffer.  This happens when someone would pan left or right.  The camera will tell you where its center is but I am looking for a way to determine what data range it is viewing in world coordinates, as in how much of the X / Y / Z axis am I seeing?  Is this something that I could acomplish with vtkSelectVisiblePoints <http://www.vtk.org/doc/nightly/html/classvtkSelectVisiblePoints.html>  ?
 
Thanks in advance,
Sarah