Easing procedures specify the rate of change of a value alpha over time. Easings may be composed to form complex animation.
The following procedures are used to control repitition by clamping alpha to the range [0, 1] in different ways.
When alpha reaches 1, start over from 0.
When alpha reaches 1, work backwards to 0. When alpha reaches 0, work forwards to 1.
The following easing functions control the rate of change of an animation: