ABSTRACT
The term rotoscoping dates back almost as far as film itself and originates in a device used to allow cartoon animators to copy live action motion. Call it cheating if you like, but many of the great animated films are
packed with scenes that were originally played by live actors or dancers and subsequently reinterpreted (not just redrawn) as animations. These days the term is used to represent any method of drawing something by hand onto film, generally involving rephotographing the hand-drawn sequence, or by drawing or painting via the screen of a computer. But just as you can use the rotoscope, or equivalent technique, to create animation from live action, or even combine animation with live action, so you can use it to create a matte. But rather than the static compositing of the glass shot or conventional matte, now the camera can move. The principles of the static matte still apply, but the methods of application are rather different. One way a so-called travelling matte can be employed is to shoot the foreground element against a background that can easily be identified as such by eye, and then the rotoscope artist can proceed to matte out the background in a process that results in a piece of film with a clear patch where the foreground action takes place, moving and changing shape with it. This is the hold-out matte. The original footage and hold-out matte are assembled into a bi-pack, and exposed via an optical printer onto raw stock. This results in the foreground action being exposed and the rest of the film still untouched by light. From the holdout matte, simple printing can create a burn-in matte. The background is shot and exposed through the burn-in matte in the optical printer to join foreground and background together into a believable illusion. In fact, the optical printer in its most advanced form can assemble several elements and, amazingly, operates without the benefit of a single bit of digital data in attendance (other than the setting of the on/off switch!).
