[vtkusers] Help!Restore the gesture of an actor

[rchqh]

Hi all,
I am programming to show images in a renderwindow.Usually,I enable 
vtkRenderWindowInteractor to control the gesture of an Actor.However,after the 
mouse operation,the user always can't restore the original position and 
orientation of the actor by rotating ,translating,scaling etc.I just want to 
set the actor on such a gesture with identified transform.But I don't know how 
to do by employing functions of vtkRenderWindowInteractor.Could anyone help 
me?

Thanks a lot!