[vtkusers] Picking a large object: slow???

[Bertwim van Beest]

I read a large unstructured grid ( ~10^3 -- 10^6 cells) which I 
visualise on the screen.
I have enabled interaction with it by using an instance of 
 vtkRenderWindowInteractor.
So far all failrly standard.

In "camera mode" (pressing "C"), the view on the grid changes 
instantaneous when I press/move the mouse.
However, when I am in "actor mode" (pressing "A") it can take 
considerable time (a couple of seconds) when I have ~10^4 cells, and 
*much* more when the grid is larger. I can see that the CPU is very busy 
on the mouse click, apparently deciding which actor is to be moved. Once 
it has found the actor, I can almost painless move/rotate the grid.

I have the feeling that too much work is being done here. I only wanted 
to rotate my grid.
Can somebody help me out how to do this faster?

Thanks in advance
Bertwim