frame, light, populate and test-shoot your work.
Import your 3d environments and then explore them, working out the best cameras and angles to shoot, moving your camera and changing lens as you see fit.
record passes and so you can play them back to show others.
give the feel and mood you wish.
Block out movement plans with simple virtual human stand-ins for actors and crew.
Edit and change so you can really get a feel for the action in the virtual space.