[vtkusers] subtract volume depending on the scalar values

[Jianlong Zhou]

Hi, all,

I want to extract a subvolume (sub-scalar range not sub-region range) 
depending on the scalar range, e.g. I want to extract a CT volume and only 
extract the scalar value between 200 and 255 and save the extracted 
volume data in this range in another raw file. Would anyone tell me how to 
do this?

Thank you inadvance.

Jianlong