[vtkusers] how to threshold slice image based on vtkImagePlaneWidget

[kdsfinger at gmail.com]

hi, all

How may I threshold the output of the vtkImagePlaneWidget? Basically,
vtkImagePlaneWidget outputs 3 slices of volume images. I hope I can do
the threshold only based on the slice, not on the whole 3D volume.
Thanks for your suggestions.

zl2k