It is common experience that while in motion; objects that are far away appear to move much slower than those near by. The same can be used in the reverse method to give an indication of depth, especially in motion pictures. The objects that are supposed to be nearer to the viewer can be made to move faster than those that are to be shown further away. The viewer automatically gets the feeling of difference in depths of the various objects
This could be a very useful technique especially in animation and simulation pictures.