Using a subclass of vtkInteractorStyle, I am able to mouse click on all the actors in the renderer and get the actor with find FindPickedActor(x,y) except for any type of line including vtkPolyLine. I have no problem selecting a vtkStructuredGrid or vtkSphereSource, for example. This is independent of how thick I set the line width as seen in the attached screen grab.

I am trying to visualize wake field of a propeller.
the field data is written in Tecplot format and have 3 scalar; u, v, w.