- Squash and Stretch
- Follow Through and Overlapping Action
- Straight Ahead Action and Pose-To-Pose Action
- Slow In and Out
- Secondary Action
Squash and Stretch
The most important animation principle is called squash and stretch. When an object moves, its movement indicates the rigidity of the object. Many real world objects have little flexibilty, such as furniture, however most organic objects have some level of flexibility in their shape.
Take for example a bouncing ball. A rubber ball bounces higher and squashs more upon impact than a hard league ball. The ease with which an object squashs and stretches defines the rigidity of the material making up an object.
When a person smiles, the shape of the face is determined by the movement of muscles underneath a layer of skin. During a smile, though the head seems to increase in size, with the widening of the mouth and jaw, it does not. The object is simply displacing its matter into the stretched shape. The most important rule to squash and stretch is that no matter how squashed or stretched out an object gets, its volume remains constant.
The squashed position depicts the form either flattened out by an external pressure or constricted by its own power. The stretched position always shows the same form in a very extended condition.
Timing, or the speed of an action, is an important principle because it gives meaning to movement. The speed of an action defines how well the idea will be read to the audience.
Timing can also defines the weight of an object. Two similar objects can appear to be vastly different weights by manipulating timing alone.
For example, if you were to hit a croquet ball and a balloon with a mallet, the result would be two different actions. The croquet ball would require more force to place it into motion, would go farther, and need more force to stop it. On the other hand, the balloon would require far less force to send it flying, and because of it’s low mass and weight, it wouldn’t travel as far, and would require less force to stop it.
Timing can also contribute to size and scale of an object or character. A larger character has more mass, more weight and more inertia than a tiny character, therefore it moves slower. In contrast, a tiny character has less mass, weight, and inertia, therefore its movements are quicker.
Timing plays an essential role in illustrating the emotional state of an object or character. It is the varying speed of the characters movements that indicate whether a character is lethargic, excited, nervous, or relaxed.
An action occurs in three parts: the preparation for the action, the action itself, and the termination of the action. Anticipation is the preparation for the action. Anticipation is an effective tool for indicating what is about to happen.
Take the swing of a bat. If the bat is swung far back, one expects the ball to fly far and away upon contact, or the batter to fall over from the power of the swing. If the bat is only pulled slightly back, we expect a ground ball, or a pop fly with very little distance. The amount of anticipation used considerably affects the speed of the action which follows it. If the audience isn’t properly prepared for a fast action, they may miss it completely. The anticipating action must be made larger or the action slower.
Anticipation can also be used to direct the audiences attention. A character looking off screen and reacting provides the audience with a cue to where an important action is about to happen.
In addition, Anticipation could be used to indicate what a character is about to do. When a person is about to steal something, their eyes shift up and down the grocery aisle, looking for security, and then at the item they wish to take. This action gives the audience an opportunity to see what the theif will take before he acts.
Anticipation could also be used to mislead the audience. When a person goes to lift a large object, their body bends over more and they widen their stance. The anticipated action would be a struggle to raise the object off the ground, however the action could result in the objects flying off of the ground and the person falling over from the miscalculation.
Staging is the presentation of an idea so that it is completely and unmistakably clear.
An action is staged so that it is understood. To stage an idea clearly, the audience’s eye must be led to exactly where it needs to be at the right moment. It is important that when staging an action, that only one idea be seen by the audience at a time.
For example, in a scene with plenty of action, the audience’s eye will be drawn to an object at rest. Conversely, in a still shot, the eye will be drawn to the item in motion. The animator is saying, in effect, “Look at this, now look at this, and now look at this.”
A personality is staged so that it is recognizable; an expression so that it can be seen;. A shy child would turn their eyes down, and slightly rotate their upper body away for the gaze of another child. The child’s actions reveal the fact that he is shy. When staging a personality, it is useful to use characteristics that clearly define the character.
A mood is staged so that it will affect the audience. The tight composition of dark trees in a dense forest, leaning in toward a scared youth; eyes glowing from within the thick; hurried breathing filling the air; the childs eye wide open. All of these elements have been clearly staged to inspire fear.
Follow Through and Overlapping Action
While anticipation is the preparation of an action, follow through is the termination of an action. Actions rarely come to a sudden and complete stop, but are generally carried past their termination point.
In figure movement, actions of the parts are not simultaneous, some parts initiate moves, while others follow. For example, the wrist leads the hand and fingers in a gesture.
Weight and Drag
Appendages or loose parts of a character or object will drag behind the leading part of the object. Then as the object comes to a stop, the looser parts continue to move taking longer to settle down and stop.
Weight of the appendages dictates the speed with which they follow the lead, heavier objects drag farther behind. The lighter the object the smaller the drag and the quicker the stop.
Slight variations in the timing and speed of loose parts makes objects seem more natural. This overlapping action makes the objects and movement more interesting.
An action should never be brought to a complete stop before starting another action. Overlapping maintains a continual flow between whole phrases of actions.
Straight Ahead Action and Pose to Pose Action
Straight Ahead Action
Straight ahead action is so called because an animator literally works straight ahead from the first drawing in the scene. This process usually produces drawings and action that have a fresh and slightly zany look, because the whole process is kept very creative.
Straight ahead action is used for wild, scrambling actions where spontaneity is important.
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 inbetween frames). This is used when the scene requires more thought and the poses and timing are important.
All of your actions must be well thought out, and the timing and poses planned so that even in the early stages, the action is clear.
Slow In and Slow Out
Slow in and out deals with the spacing of the inbetween drawings between the extreme poses.
By default, interpolation of an objects inbetween positions between extreme poses are evenly spaced, and graphed as a straight line from one value to another. “Slowing out”(ease out) of one pose, then “slowing in” to the next pose generate inbetweens clustered on either end of the distance between the extremes, with less inbetweens toward the center. When graphed, an ease in and out is graphed as a spline from one pose to the next.
Eases can be used to create acceleration and deceleration. As a ball bounces, it accelerates and decelerates. When you drop the ball, it gains speed as it approaches the ground. After the impact on the ground it bounces and begins to loose speed as it reaches the apex of its bounce. The graph of the balls acceleration would show an increasing distance between the balls positions as it came closer to the ground. Similarly, the graph of the balls bounce off the ground would indicate a decreasing distance between the balls positions as it reaches the apex.
With this type of spline interpolation, it is common to have spline overshooting at extreme poses when there is a large change in value between them over a small number of frames. Tangency handles can be used to manipulate the tension of the spline, reducing the overshooting and achieving the desired inbetween.
The visual path of action from one extreme to another is always described by anarc. In nature, arcs are the most economical routes by which a form can move from one position to another.
Such arcs are used extensively in animation, since they create motion that is more expressive and less stiff than action along a straight path.
Exaggeration can be used in animation with great results.
However the key to proper use of exaggeration lies in exploring the essence of the action or idea, understanding the reason for it, so that the audience will also understand it. If a character is sad, make him sadder; if he is bright, make him shine; worried, make him fret
If he is angry, make him furious.
A scene has many components to it including design, action, objects and emotion. Exaggeration of every element in a scene creates a feeling of uneasiness in your audience. Everything is distorted and unrealistic. Find a balance in your scene. Allow your audience a grounds for comparison of the exaggeration and by so doing, the whole scene will remain very realistic to them
Secondary actions are important in heightening interest and adding a realistic complexity to the animation.
If a secondary action conflicts with, becomes more interesting, or dominates in any way, it is either the wrong choice or is staged improperly.
Facial Animation Dangers
Generally, in facial animation, the movement is a secondary action, subordinate to the bodies movement. The danger with facial animation isn’t that it will dominate the scene, but that it will not be seen. The change in expression should happen before or after a move, changes in the middle of a major move will mostly likely go unnoticed.
Where the live action actor has charisma, the animated character has appeal.
Audiences like to see a quality of charm, pleasing design, simplicity, communication, or magnetism. A weak drawing or design lacks appeal. A design that is complicated or hard to read lacks appeal. Clumsy shapes and awkward moves all have low appeal.
Every pose in animation has to be solid, it has to guide the viewer eyes with the right line of action and flow lines. To make a pose to be believeable it also has to have the right weight distribution and the right staging of the characters to make it interesting to watch.
In creating an appealing pose for a character, one thing to avoid is called “twins”, where both arms and both legs are in the same position, doing the same thing. This creates a stiff pose that is unappealing. Vary the parts of the body a bit, including the facial features, makes a character more appealing.