The Principles of Animation
Covered on the following pages: 1. The Classic Principles of Animation 2. The Extended Principles of Animation 3. The Physics of Animation 4. Camera Techniques for Animation
Classic Principles of Animation
This first section looks at the 2D and 3D applications of the original 12 Principles of Animation introduced by Disney in the 1930s. These include Squash and Stretch, Anticipation, Staging, Straight Ahead Action VS Pose to Pose Action, Follow-Through and Overlapping Action, Slow-In and Slow-Out, Arcs, Secondary Action, Timing, Exaggeration, Solid Drawing, and Appeal.
Squash and Stretch
Squash and Stretch is best described by animating a bouncing ball, as shown at right, where the ball squashes when it hits the ground, deforming and becoming more flat, and then reforms as it continues back up again. A more exagerated version is shown at right, where the ball stretches upwards and then squashes against the walls at it bounces. This can be applied character movements (as during a sneeze, scream, or grimace) that exagerrated the movement and add a comical and dramatic sense to the animation.
Anticipation is a preparation for an action of some kind; in the animation above right, the ball is demonstrating anticipation as it trembles and then stretches upwards, getting ready for take-off. This can also take the form of a vase tipping and threatening to fall from a window, or a batter winding up to hit a ball. The classic example of anticipation is the cartoon character whose body leans back, legs already moving in a running motion, before the character takes off.
Staging is presenting a scene so that the intent or mood of the scene will be clearly communicated to the audience. By paying attention to the character position, character movement, camera movements, and carefully considering all scene content, this can be achieved. Each of these factors can be used to guide the eye of the audience, and can contribute to or detract from the intent or mood of the scene. In the example at right, a scene is being worked out depicting a confrontation between three characters.
Straight Ahead vs Pose to Pose
Straight Ahead action is where you draw or animate the character from beginning to end, every single frame, without generating keyframes first. Pose to Pose action (also called Keyframing) is where there are a series of poses created, residing on “Key” Frames and the “tweens” or in-between frames are generated to complete the animation. In the example at right, the character goes from a root pose to a pose that prepares for a jump. The jump is made up of several poses, which are then tweened by the animation software automatically. Most animation today is done with Pose to Pose because it is faster and more efficient.
Follow-Through and Overlapping Action
Follow-through is easiest to visualize with a sports example – a golfer hits the ball, but the club doesn’t stop there, it continues through its arc, long after the ball has been hit, as the golfer’s body twists. Overlapping Action is what is happening with the golfer’s limbs during this process; the start and stop points, as well as motion, overlap. The movement of a palm tree in the wind, shown at right with onionskinning enabled, illustrates this process.
Slow-In and Slow-Out
Also known as Ease-in, Ease-out; the bouncing ball example at right demonstrates this principle as the ball “eases in” to its fall (on the left), gathering speed while dropping, bounces on the floor, and “eases out” of its motion, gradually slowing while the forces of gravity take a hold on it. Ease-in and Slow-in are the same basic idea; you are slowly accelerating the motion of the object. Ease-out and Slow-out are also synonomous – you are slowly reducing the speed of your object’s motion. Faster movements show fewer keyframes, slower movements show more keyframes.
Everything living tends to move with arc-based motion. When a character runs or swings their arms or legs, those limbs are rotating. Feet rotate about ankles, lower legs rotate around knees, and entire legs rotate around hips. Whether the character is animated using keyframes or motion capture, key points in the anatomy of the character can be selected and moved or rotated to generate smoother arcs and therefore more realistic movement. Another aspect of the arc in motion is with the sinusoidal movement of the hips and head, up and down as the figure progresses across the screen.
Secondary action, often referred to as secondary motion, is probably the most commonly noticed principle which applies well to both comical and realistic animation. Secondary action can be seen in organic and mechanical movement, when a body that is only loosely attached to the body in primary motion moves. When a character runs, and their hair or some part of clothing echoes their body’s up and down motion, secondary action is in play. When a car goes around a corner too fast and a loose door swings open, or as shown at right, when a box in the back of a truck bounces around, we are seeing secondary action.
Timing and Spacing
Timing is the precision with which character movement occurs, and how long it lasts. How many frames per second is the animation, and how many frames does the character need to take a step, stretch their neck, yawn, blink, or throw a punch? It all comes down to timing. Spacing is the physical representation of timing. In the horse study shown at right, the different positions of the horse are spaced one keyframe apart; the distance between the legs indicate how fast the leg is moving through space; the more distance, the faster the movement.
Exaggeration is used to make the character’s expression or movement more dramatic. At right, a car hits a brick wall and the result is that it is smashed to half its length; even the wheels and tires are squashed. While this is blatant exaggeration, there are a whole range of possibilities. A more subtle exaggeration can be used to make the motions of a character read better, much the way that stage actors must sometimes overact so that their poses and expressions read at a distance.
Solid drawing refers to competent, drawings that are well-proportioned, demonstrating good form, with appropriate volume and weight to them. These factors help to make a character appear more real and lifelike.
Appeal is a somewhat deceptive term for what might better be described as charisma. The character should be well-developed and unique in form, color, texture, pose, expression, and movement (as in walk/run cycles and other physical movements). The design should be clear and clean. This individualized distinction helps to create character recognition and appeal, as well as making the character more believable for the audience. Appeal is necessary for all characters to be more authentic.