I noticed when I change between rendering contexts the display lists for objects are thrown away and there is a delay to rebuild these display lists. To remedy this I turned on immediate mode rendering on the mappers. There is a slight speed difference on my TNT2 but not enough to worry about.
 
Tom C.
 
I have an application that uses 4 render windows  - 1 for 3D objects and 3 widgets for 2D images.  I am noticing
considerable rendering delay switching between the 2d and 3d windows. Especially, when I come from interacting with
the 2D images to the 3D render window. Depending on the data size, it takes a significant time to do the first
rendering and after that, the interaction (using render window interactor) works normally.  Is there some major
overhead between switching pipelines (these are independently constructed vtk pipelines). Note that nothing in
the 3D widget has changed except for the camera position.