A major advance over rear projection is front projection, which uses a special screen material to allow the plate to be projected from the front of the screen. This results in a much sharper and more saturated image. Although the technique had been used experimentally for some time, it was during the filming of "" that the modern version was fully developed. In this case it was used to avoid costly on-location shots in Africa during the opening scenes of the movie, but the effect was also used throughout the film for a variety of shots into or out of the windows of spacecraft. "2001" also used rear projection to produce computer screen effects.