[vtkusers] vtkImagePlaneWidget: interpolated cursor position

[dean.inglis at camris.ca]

John, David,


1) vtkIPW allows you to set the picker, so you could 'listen' in as
an obsever through the callback mechanism, although I've never tried.

2) when I made the cursor feature, what I really wanted was what 
you are requesting John: interpolated voxel data and not
nearest neighbour as it is now.  If David or anyone else would
like to add that in .... :)

Dean