[vtkusers] Picking

[Maneesh Yadav]

I am still a little confused about the new (heck even the old) picking
stuff...But I would really like to be able to have pick levels (i.e. be
able to pick a molecule, residues and atoms)...can I dynamically adjust
"pickability" of actors in the scene (like set up a series of picklists)
easily or at least in a straightforward manner with the way things are
setup now?