[vtkusers] edges between moving assemblies

[creusot]

Hi,
I have a small problem to design the scene I want with VTK.
Basically I would like to have two Assemblies composed of several Actors 
(small spheres) and a set of edges between the two Assemblies connecting 
a subset of those spheres.
Creating the Assemblies is very easy but I don't know what to do for the 
edges.
If I create an edge as an Actor using the initial position of the sphere 
then the edges doesnt move when I move one of the Assembly compare to 
the other.
How can I create a line or a tube which extremities are from two 
different objects and are not fixed?
Best regards,
Clement.