Animator Max Fleischer developed the original concept of rotoscoping. It involved projecting a moving image on a glass and tracing it frame-by-frame. It was viewed as a way to more realistically capture motion. The projected image could be used as a guide to draw a cartoon-like character whose motion (not necessarily the look) is emulated.
Fleischer’s younger brother, Dave, was working as a clown at Coney Island. Dave became the early inspiration for one of Max’s first characters, Koko the Clown.
Film footage of Dave in costume would be projected onto an easel covered by glass. Each frame of footage would be traced onto a piece of paper, using a new sheet of paper for every frame. The result was the first rotoscope animation.
I remember seeing Koko the Clown cartoons on TV when I was young (although I did not realize how old they were, even then) – now you can catch some on YouTube and I recommend my readers check them out.
Max Fleischer went on to produce Betty Boop and Popeye cartoons.
Max Fleischer’s Betty Boop and Walt Disney’s Mickey Mouse were becoming the two most famous animated characters. Both animators were constantly pushing revolutionary techniques.
Disney would adopt the rotoscoping technique, but in a different way. Disney would film live-action footage as a reference for character movement. This would play a major role in the production of “Snow White and the Seven Dwarfs” and subsequent features.
Rotoscoping is used for visual effects (VFX) in live-action movies. Moviemakers would create a silhouette of an image (known as a matte) that would be extracted to be placed on a different background. Think of a giant person walking amongst skyscrapers. The person and the skyscrapers are filmed separately and then combined.
Today, computers and green screens, along with motion-tracking software, are used to achieve the desired effects. In motion capture, a performer wears a skin-tight outfit composed of reflective balls on joints (e.g., knees). In addition, these reflective balls are placed on the face and other exposed areas where motion is desired to be captured. Together it is called performance capture.
The visual effect of the lightsaber in early Star Wars films was created via rotoscoping over a stick.
In conclusion, rotoscoping in cartoons is an animation technique using live action as a guide. In live-action film, it is a generic terminology for the various methods of creating a composite image in the frame. Today the term motion capture is also used.
For more information on rotoscoping, see Additional Information below.
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Additional Information
Wikipedia: Rotoscoping Koko the Clown
Rocketstock: Rotoscoping: From Early Animation to Blockbuster VFX
TV Tropes: Rotoscoping Motion Capture