Arcs - Animation Principles

Arcs are in most movement that we encounter in day to day life as most naturalistic action follows a series of curves and arcs; very few natural actions are linear, the majority of such action occurs in more mechanical situations.

Because of this arcs must be incorporated into animated action in order to sustain believability. However sometimes animators may choose to disregard this approach, in order to create more emphasis on the keys rather than the movement. John Kricfalusi did this when producing "Ren and Stimpey" creating more snappy action.

Using an arc within your animation movement essentially means that the action follows a curve of action rather going in a straight line.

An example of arcs used in animation:

An example of animation ignoring the arcs approach:

I intend to produce my own short line tests illustrating this approach further, alongside more in depth research.

References:

"Animation the Mechanics of Motion" Chris Webster. Pages 50-5

"Animators Survival Kit" Richard Williams. Pages 90-2