Extended Principles of Animation
Since the first 12 principles of animation were codified by Disney in the 30s, there have been technological and artistic developments that are covered in this section. Some of these principles are implied in the original principles and some are not. This list may vary depending on who you talk to.
Shape, Form, and Anatomy
The shape or form being used for the animation is important for realism, believability, and consistency. A realistic horse animation needs the same angles expressed by the outer contours in this rendering, but even the cartoon horse needs some suggestion of these angles, or it will begin to look like a stuffed animal. Suggesting the anatomy of the horse even in a cartoon gives it recognizability and authenticity. And even if the creature being animated does not exist in reality, borrowing forms and anatomy from creatures that do exist can make the imaginary creature more authentic.
What is the object, and how much does it weigh? How can we tell this? How is the weight of the object apparent by the way other objects and characters interact with the object? Why is it moving? What is the purpose to the movement? The image at right illustrates how a character’s entire posture changes when struggling with too much weight. Note that with a heavy object, the character has no choice but to bring the object as close to their own center as possible. Other tell-tale signs here include supporting the object with a body part (the knee), and extending the back leg to balance the forward posture.
Action and Reaction
Action and reaction is illustrated by a rocketship, the most well-known example of this physical law; however, this principle applies to characters as well; not only physically, in that a pushed character will react to whatever pushed it by pushing back or falling down but actions and reactions can take place in dialogue and in emotional reactions of characters when things are going well or not so well. Sometimes the reaction is instant, as in the rocket – but the reaction can also be delayed, especially when dealing with emotional interactions.
Action Ahead of / Action Behind the Story
Action Ahead of the Story and Action Behind the Story can add great tension and suspense to an animation. Action ahead of the story is illustrated by the upper image at right; the surfer is seeing something we as the audience cannot see. This adds suspense. Action behind the story is illustrated by the lower image at right; the surfer is not aware that there is a shark following her rather closely. The tension in this case comes from not knowing how the character will react to what we already know about, and how it will turn out.
In 3D animation a basic perspective is often handled automatically through the camera, unless there is a special angle you are working towards. With 2D animation, the perspective must be drawn with either One Point perspective (as shown at right), Two Point Perspective, or Three Point perspective. An unusual perspective, whether the animation is 2D or 3D, can make the animation much more interesting. When using 3D animation, even though the perspective is handled automatically, it is still important to try and achieve interesting views of the object you are focusing on.
The overall direction a body is moving can greatly enhance or detract from an animation. Direction can also be exaggerated to magnify the effect of a character’s movement; an example is the comic case of a character who is smashed flat by being slammed by a door, or the hunched up then stretched out form of a character beginning a run. Whether exaggerated or not, the direction of the character should always match the intent of the animation and what the character is doing at that time.
Tension and Relaxation
Tension can refer to the emotional or physical state of the character as well as to the state of the control curves that govern a rigged character’s movement. The movements of a character who is under great emotional or physical strain are tighter and more tense than those of a character who is happy-go-lucky in their movements. One character is more controlled, even quick and precise; another is loose, flowing, with a slower reaction time. Adding these kinds of nuances adds depth to character development, and helps to differentiate one character from another.
Depth and Volume
Depth can be implied in even a 2D cartoon by putting different objects in front of other objects, and by fading the colors of the more distant objects. Depth is also implied by making more distant objects smaller. Many 2D and 3D animations use shadow to depict volume, whether it is drawn by hand, proceduralized by gradient features, or automated by light placement as in the case of 3D animation software. Depth and Volume add to the authenticity and immersion of a scene, whether you use 2D or 3D techniques.
Working from Extreme to Extreme
Extreme to Extreme refers to positions for 2D and 3D characters. In a walk cycle, it is more straightforward and efficient to draw the extremes of the walk cycle first, and go it to create the other key frames afterwards. This can be seen at right, where the biped (skeleton) for a game character is being animated for a backwards run cycle. The first frame, at right, is one extreme, the second position in the middle is the furthest the feet ever spread apart, and the third position is where the feet are closest again, nearly the same as in the first frame.
Rigging is a 3D animation technique where bones or some other skeletal structure are assigned certain motion constraints (so that an elbow cannot move the wrong direction, for example), and then different parts of the character mesh are assigned to each bone. Later, in the animation process, when the skeletal members are animated, the character mesh moves also. Inverse or Forward Kinematics and Controllers can be applied to the rig as well, making the process easier to control and adjust. The character at right is in the process of having its mesh vertices assigned to different bones in the rig, through the use of “envelopes”.