craft director tools calculates or 'simulate' the motion of objects like cars with the aid of complex algorithms designed to recreate physical events from the real world. a car, for example, tilts forward when it stops. that is because of the momentum it has from its forward motion. craft director tools' algorithms calculate how much a car ought to tilt - and simulates that event inside the computer. the same kind of simulation is done for airplanes, helicopters (which are extremely complex to simulate) motorcycles and boats.