The 12 Principles of Animation

Below are some brief definitions of each of the twelve principles of animation:

1) Squash and Stretch - defines the rigidity and mass of an object by distorting its shape during an action. When an object squashes or stretches, it appears to be made of a pliable material, only totally rigid objects remain stiff in motion, but with living creatures the shape will deform in some way. Objects that are partially pliable and partially rigid should have only the pliable parts deform.

A hinged object can squash and stretch without deforming

An important rule is that the volume of the object should remain constant at rest, squashed, or stretched. If this rule is not obeyed, then the object appears to shrink when squashed and to grow when stretched. 

2) Timing and Motion - gives meaning to movement, both physical and emotional. Spacing actions define the weight and size of objects and the personality of characters.

3) Anticipation - can be the anatomical preparation for action or a device to attract the viewer's attention to the proper screen area and to prepare them for the action. A well timed anticipation can enable the viewer to better understand a rapid action, e.g., preparing to jump and then leaping off-screen.

4) Staging – presents an idea so that it is unmistakably clear to the viewer, this idea can be an action, a personality, an expression, or a mood. An important objective of staging is to lead the viewer’s eye to where the action will occur so that they do not miss anything.

5) Follow Through and Overlapping Action - is the termination of an action and establishing its relationship to the next action. In the movement of a complex object different parts of the object move at different times and different rates, heavier parts lag farther and stop slower.  Overlapping means to start a second action before the first action has completely finished. This keeps the interest of the viewer, since there is no dead time between actions.

Here is a quote about overlapping from Walt Disney:

"It is not necessary for an animator to take a character to one point, complete that action completely, and then turn to the following action as if he had never given it a thought until after completing the first action. When a character knows what he is going to do he doesn't have to stop before each individual action and think to do it. He has it planned in advance in his mind.

6) Straight Ahead Action - in hand drawn animation is when the animator starts at the first drawing in a scene and then draws all of the subsequent frames until he reaches the end of the scene. This creates very spontaneous and zany looking animation and is used for wild, scrambling action.

6) Pose-to-Pose Action - is when the animator carefully plans out the animation, draws a sequence of poses, i.e., the initial, some in-between, and the final poses and then draws all the in-between frames (or another artist or the computer draws the in-between frames). This is used when the scene requires more thought and the poses and timing are important.

7) Slow In and Out - refers to the spacing of the in-between frames at maximum positions. It is the second and third order continuity of motion of the object. Rather than having a uniform velocity for an object, it is more appealing, and sometimes more realistic, to have the velocity vary at the extremes. The name comes from having the object or character "slow out" of one pose and "slow in" to the next pose.

8) Arcs – are the visual path of action from one extreme to another is always described by an arc. In nature, arcs are the most economical routes by which a form can move from one position to another.

9) Exaggeration - does not mean just distorting the actions or objects arbitrarily, but the animator must carefully choose which properties to exaggerate. If only one thing is exaggerated then it may stand out too much. If everything is exaggerated, then the entire scene may appear too unrealistic.

10) Secondary Action - is an action that directly results from another action. It can be used to increase the complexity and interest in a scene. It should always be subordinate to and not compete with the primary action in the scene.

11) Appeal - means something that the audience will want to see. This is equivalent to charisma in a live actor. A scene or character should not be too simple (boring!) or too complex (can't understand it). One principle to achieve this is to avoid mirror symmetry. Asymmetry tends to be more interesting and appealing.

12) Personality - is the objective of the principles previously discussed is to give the characters in an animation a personality those appeals to the viewers. The different principles should be applied in a fashion to produce a consistent personality. This means that the animator must have a good idea of the desired personality before beginning the animation.