[vtkusers] plot a huge amount of spheres

[curator]

Hi all,

I am able to draw a vtkSphere with its own vtkSphere, vtkActor and 
vtkMapper equipped together. Now if I need several spheres, I add 
multiple instances of this stuff for each sphere and add them all up to 
the same renderer - so far, so good.

Now I need to draw a really huge amount of spheres, which are all 
identical except the position. Is there any more efficient way to to 
that than just creating N vtkActors, N vtkMappers and N vtkSpheres?

regards,
curator