[vtkusers] Picking smaller items than actors

[Kent Vander Velden]

  I have a scene with only few actors, but a number of spheres created
using vtkSphereSource and vtkGlyph3D.  I need to be able to pick a
single sphere from this scene, but have only been able to select an
entire actor.  After selecting the sphere there also needs to be some
way to identify what data was used to generate this sphere.  I have
experimented with vtkCellPicker but am not sure if this is what I
should use nor do I understand how to go from a cellId to the geometry
of that cell.  Could someone provide some guidance?

  Thanks!

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Kent Vander Velden
kent at iastate.edu