Special effects cover the practical, real time enhancements to a scene as it is filmed .
Rear projection involves projecting either a still or moving picture onto the rear of a translucent screen in front of which live-action is photographed so that both the background on the screen and foreground action are combined into a single image on the exposed film. Forced perspective sets allow the illusion of greater distance than the available space might permit, by tapering all constructed angles to diminish more rapidly than reality. This works as long as the camera doesn't shift position to the right or left. More recently, the creation and addition of entirely synthetic animated characters, settings and environments has become the most publicized part of the visual effects industry, and appear in some form in almost every major film we see today, even if limited to a few digital matte paintings to set the scene. Jeff Olson joined ILM in 1985 as set builder and modelmaker on Howard the Duck .