[vtkusers] controlling render progress

[Thomas Faust]

Hi users.

What is the best way, to see the progress of a render process?

I have a big model, that takes some seconds, to rerender after interacting 
with it. I want to get some informations about the progress of this render 
process. I was trying to get 'ProgressEvents' from the VolumeMapper, but this 
failed. The vtkRenderer itself don't have ProgressEvents, just a StartEvent 
and EndEvent.
Which events i have to watch, to see the render progress?

Thanks, Tom