Principles of Animation

At its core, any animation entails showing a viewer a series of images in rapid succession. The viewer assembles these images, trying to build a coherent idea of what occurred between them. The perceptual system notes the changes between frames, so an animation can be understood as a series of visual changes between frames. When there are a small number of changes, it is quite simple to understand what has happened, and the viewer can trace the changes easily. When there are a large number of changes, it gets more complex.

The Gestalt perceptual principle of common fate states that viewers will group large numbers of objects together, labeling them all as a group, if they are traveling in the same direction and at the same speed. Individual objects that take their own trajectories will be seen as isolates, and will visually stand out. If all the items move in different directions, however, observers have far more difficulty following them. Perception researchers have shown that viewers have difficulty tracking more than four or five objects independently—the eye gives up, tracking only a few objects and labeling other movement as noise (Cavanagh and Alvarez 2005).