animation

What animation is

Animation is a mode of the moving image in which the appearance of motion is built up from a sequence of individually made images rather than captured by continuously filming a moving subject. Each image is produced on its own — drawn, painted, posed, or computed — and the images are recorded or ordered so that, when shown in rapid succession, the differences between them read as movement. The technique relies on the same perceptual basis as all motion-picture display: a series of still pictures presented quickly enough is seen as continuous change rather than as separate images.

The distinction from live action lies in how the images originate. In live-action recording, a camera samples a scene that is already moving, and each frame records an instant of that real motion. In animation, no such continuous motion exists in front of the camera; the motion is authored, image by image, and only comes into being when the finished sequence is played. Because every frame is made deliberately, animation shares much of its craft with visual-effects, which likewise constructs imagery outside the moment of live capture, though animation typically presents its images as an avowedly drawn or modeled world rather than one blended with photographed reality.

Frame-by-frame construction

The common principle across all forms of animation is frame-by-frame construction: the work is assembled one frame at a time, and the illusion of movement depends on how much a subject changes from one frame to the next. A film is shown at a fixed frame rate, and animators may make a new image for every frame or hold each image across two or more frames — a practice long described as working “on ones” or “on twos.” Holding images across multiple frames reduces the number of separate pictures required while still preserving the perception of smooth motion, and the choice of interval affects both the fluidity of the movement and the labor involved.

Principal techniques

Traditional animation, also called cel animation, builds movement from a succession of drawings. In the classical photographic method, the moving parts of a scene were inked and painted onto transparent sheets called cels, which were laid over a separately painted background and photographed one frame at a time, so that only the changing elements had to be redrawn for each frame.

Stop motion produces movement by photographing physical objects — puppets, models, clay figures, or other articulated forms — one frame at a time, moving the subject a small amount between exposures. When the resulting frames are played in sequence, the objects appear to move on their own.

Computer animation generates its images by computer. In three-dimensional computer animation, objects, surfaces, lighting, and motion are modeled as data and then rendered into finished frames; motion is typically defined at selected key points in time, with intermediate positions calculated between them. In all three approaches the underlying method is the same — a sequence of individually made images shown in rapid succession — while the means of making each image differs.