1. Time-lapse: Photographing a scene only at selected intervals, creating an illusion of spontaneous change when played back. The earliest form of animation, predating live-action cinema; various playback methods for time-lapse photos were established by the 1830s.

2. Stop-motion: Photographing a single object and moving it while the camera is stopped. Can be done with paper cut-outs, puppets with poseable armatures, or even cooperative human actors (pixilation, which with this spelling has nothing to do with computers, meaning “possession by evil spirits”). Quickly adopted in the 1900s for visual effects in early silent films.

3. Replacement: Replacing the object being photographed with a different object while the camera is stopped. Classical animation is replacement animation using pencil drawings on paper or ink on plastic cels; this technique dominated animated feature production until the late 1980s. Less common variations use photo collage or sculpture. First came into wide use with “lightning artist” vaudeville acts in the 1910s, where audiences would watch an animated film being made.

4. Rotoscoping: Using live action as a frame-by-frame reference for animation. Traditionally done by projecting film footage and tracing it, a common technique by the 1940s. Motion capture is a modern variant of rotoscoping, in which the analysis of movement is done with a computer instead of by hand.

5. Analog Computer Graphics: Also known as computer-assisted graphics, generating images via commands sent to an external hardware system, such as a motion-control camera or CRT electron beam. Early examples exist from the 1940s; videotape-based systems called video synthesizers were in use by the 1960s.

6. Digital Computer Graphics: The most common form of animation in use today, generating images within a computer system by manipulating a set of numerical values in memory, instead of through the direct control of hardware. Common digital representations of an image are as a grid of colored dots (pixels), a set of spatial coordinates (vertices), or a combination of both. The best-documented early examples appear in the 1960s and wide adoption occurs by the 1990s.

For a more detailed timeline, see A Biography of the Pixel by Alvy Ray Smith.