It's often been treated with scorn, often viewed with suspicion. To many it is "mere rotoscoping", a crutch that no "true animator" would ever stoop to use. If Walt Disney were alive today he might hear, "You used rotoscoping? ...Wait! Say it isn't so!" One can almost imagine "Rotoscopers Anonymous" groups springing up to purge the industry of this malady. The cause of all this is a technique where one takes live action footage and uses it to create animation by copying, usually by tracing, the moving images, frame-by-frame, onto animation paper. These hand-drawn images are usually altered to create the final animated images.
Rotoscoping was invented around 1915 by Max Fleischer, who would eventually own the studio that would bring Betty Boop and Popeye to life. While working as an art editor at Popular Science Monthly, he had begun to wonder if it might be possible to use mechanics in the process of making animated cartoons. Along with his brothers, Joe and Dave, he conducted an experiment to see if his theories were correct. Joe, a wizard at machinery, built the devices necessary for the new process of 'rotoscoping' and Dave posed in a clown suit for the creation of the live action reference footage. The cartoon character that came out of this was at first known simply as the 'clown' but later was given the name of "Koko the Clown" and the cartoon series was called "Out of the Inkwell." The cartoons were immediately popular. The realistic movement added a whole new dimension but it was the clever stories and gags that sustained the series. A reviewer for the New York Times wrote in 1919, "After a deluge of pen-and-ink 'comedies' in which figures move with mechanical jerks with little or no wit to guide them, it is a treat to watch the smooth action of Mr. Fleischer's figure and enjoy the cleverness that animates it."
For much of its history rotoscoping has been used in only its most basic form -- carefully tracing every frame or every other frame of the live action film footage of the desired moving images. This has been done not only for character animation but also for moving backgrounds, for moving inanimate objects, and for many things moving in perspective in order to precisely capture the action.
Disney's "Snow White" went well beyond the normal methods. Although it has been significantly downplayed by historians since its 1939 release date, rotoscoping was extensively used as the basis for the movements of the least cartoon-like characters in the picture (Snow White, the Wicked Queen, the Woodsman, and the Prince). Publicity releases of the time spoke of using reference footage. The term "reference footage" -- material to be referred to where and when appropriate -- is much closer to the methodology that was used than the usual approach of always closely following the action. Much of the live action footage was used only to create extremes (the beginnings or endings of actions) for creating "Key" drawings which would then be in-betweened in the usual manner. This left it more up to the animator to decide the timing of the movement.
To create the reference footage for the character of Snow White, Disney hired a Los Angeles dancer named Marjorie Belcher. She gained fame later as a dancer in film musicals under the name "Marge Champion". It would not be too much of a speculation to say that her movements must have been very carefully planned and choreographed in advance. This would prevent wasted movement and having the action purposely 'overplayed' would make Snow White's character blend in more easily with the traditionally freehand animated characters. "Snow White" being the first feature length animated film, was a huge financial and artistic risk where the usual two-dimensional cartoon characterizations would not work. It is not surprising that Disney Studio would rely on rotoscoping to get the film done within as reasonable period of time as possible and within as tight a budget as possible. What is remarkable is that the practice of rotoscoping was not used in a slavish way, but rather with imagination and great selectivity.
Rotoscoping has not been limited to the production of animated films. It has also been used as a way to learn the art of animation. Use of it for this purpose began in the silent era and it became known as "action analysis". In Leonard Maltin's book, Of Mice and Magic, Walter Lantz recalls, "I would take the old Charlie Chaplin films and project them one frame at a time, make a drawing over Chaplin's action, and flip the drawings to see how he moved. That's how most of us learned to animate." Action analysis later became a cornerstone of Disney's in-house studio art courses.
"It's a mechanical process and looks that way on the screen." In truth, rotoscoped footage looks only as mechanical as the animator makes it. If this comment were interpreted broadly one could say that animation (and with it film) itself is a mechanical process.
"Using rotoscoping (not to mention computers) is being lazy." Animation form the beginning has been a very labor intensive process and methods and tools have been developed since its inception to save work. To not use these labor saving methods and tools would take us back to the days when acetate cels weren't invented and you had not only to animate every frame but had to redraw the background every time as well.
"Rotoscoping footage stands out like a sore thumb." True, if it isn't done with care. In order to be successful, rotoscoped elements must not clash with the rest of the animation in a scene and have to look appropriate. How loosely of tightly the rotoscoping is done as well as how realistic the element being created is can make a lot of difference.
"Animation has a magic that rotoscoping does not." The effect of rotoscoping all depends on what the animator adds to it. Rotoscoped footage created by only tracing and little else adds very little to the finished film. But if movements have been carefully choreographed beforehand, proper care was given to the design of a character, and the animator's skills were used at the proper points to add just the right amount of exaggeration to movement and facial expressions, then this sort of footage can have all the magic that footage created strictly from an animator's head and with their hand can have.
Rotoscoping, when used as a learning tool, can enhance traditional freehand animation. Although it has been used mostly as a time-saving device, rotoscoping can actually improve an animator's skill. However, the opportunity must be taken to study what is happening in the frame.
An experienced freehand animator can enhance the look of rotoscoped footage if their expertise is used to determine which details to exaggerate. Small details in live action film which are often too subtle to translate well during rotoscoping can be exaggerated to "read" better. For instance, a smile or some other change in expression that might be rather difficult to see otherwise can not only be made to "read" but can add much to the scene if an animator uses their skills well. An animator can also use their skills to enhance movement using such concepts as "squash and stretch" or spacing patterns to make a heavy character (such as if an actor is portraying an elephant) show more weight or to make a dancer seem to float in the air. This can make rotoscoped footage looked more lively and "animated". Lack of these important qualities is what is commonly criticized about rotoscoped action and is what most of the time gives rotoscoping its bad reputation.
The practice of rotoscoping can cover a whole range of approaches. In its most basic form every frame or every other frame is traced and used mostly "as-is" and altered very little. A looser approach is to use only the extremes and to fill in all the frames between by freehand means. This still saves work and gives the animator more freedom in the timing of the action. (Of course, in the more usual approach, drawings can be added or deleted to do the same thing.) An alternative approach to either of these is to very loosely draw over the original figures. This gives a much more spontaneous appearance and for certain kinds of films is the sort of asset that rotoscoping in its strictest form would not normally be able to provide.
Frames from the live action footage do not even have to be traced. An animator can look at a frame of the referenced film on a viewer and draw freehand -- either the image as it exists on the original film or draw their character in the same exact pose as the actor. This approach solves a lot of problems if your cartoon character does not happen to have the same proportions as a natural human figure. This very likely how Snow White was drawn. (Snow White stood five heads high while a natural human figure stands around six heads high. This would have presented problems had the footage been directly rotoscoped.)
Rotoscoped and freehand animation can exist side-by-side if both are used intelligently together. Both have their place and their purpose. Rotoscoping, by no means, eliminates the need to develop animation skills and knowledge. These things are still necessary if you wish to use it effectively. The fairly recent introduction of computers is blurring many boundaries and turning many cherished beliefs about animation upside down. The very notion of animation is being changed by something called "performance animation" (a process where the movements of an actor directly affect the movement of an on-screen character in real time). Even with that new way of doing things the basic understandings of movement and action still affect the success of the project -- knowledge that is (or should be) part of an animator's basic set of knowledge -- things animators take for granted like "squash and stretch" and concepts like "anticipation". There will always be a need for animators in one form or another.
What really matters is not how a project was created but the magic that is hopefully created when the work is finished. A film still has to be entertaining, no matter how beautifully animated it is or what methods were used in its making. To believably create that other world up on the screen (no matter what kind of screen it may be), it's up to animators to use ALL their tools wisely and effectively and with imagination.