Traditional Principles of Animation
Many people assume that if you build a good-looking model, it will simply come to life all by itself. Unfortunately, this couldn't be farther from the truth. A poorly constructed animation will typically suffer from objects moving in an awkward and unrealistic manner. The motion you create in your scene is an extremely important element of your overall product. You must design and execute your movement with as much care as you give to designing the objects in your animation.
An analysis of unsuccessful animation usually reveals too little motion or motion that is not life-like. So how does motion become part of your overall design? Planning must begin immediately—even before you begin to build your scene.
Below, you'll find a list of principles that the traditional masters of animation have discovered, learned and applied in their journey to learn their art. Applicable to both traditional 2D animation and computer 3D animation, every quality animated film makes use of at least a few of these basic principles developed at the Walt Disney studios during the 1930s. Believable movement starts with applying these concepts. As you continue to gain experience and knowledge, you'll come to realize just how important these techniques are. Every animator is expected to not just know these principles, but to apply them to their work. Memorizing them isn't enough. Knowing when, where and how to apply them is what's important.
Anticipation is a preliminary action that sets up a primary action. It cues or prepares the audience for what is about to happen. Let's look at an example. Let's say that a steel cable is being stretched extremely tight by two opposing forces. Before the cable snaps in two, you position your camera for a close up on the actual breaking point. The close up shows the cable fraying as more and more tension is applied. Seeing this, the audience automatically anticipates what's about to happen (the eventual breaking of the cable).
In some cases, anticipation is needed physically. For example, before you can throw a ball, you must first swing your arm backwards. As the arm goes back, the audience anticipates it coming forward and releasing the ball. more important than just audience anticipation... there is a need for a set up to the coming movement. every movement requires anticipation and recovery. there is a need to show a transfer of weight before performing an action. it is here where the action is set up.
Anticipation is also required to simulate real motion. If an object is at rest, some preliminary action that transfers energy to the object must occur so that it can use that energy to execute the primary action. Before a character can jump, they must crouch down and swing their arms for counterbalance. By seeing the crouch, the audience anticipates that the character is about to jump.
Squash and stretch
The principle of Squash and Stretch implies that no matter how much an object deforms, it must always maintain the same apparent volume. Proper use of Squash and Stretch illustrates just how dense or rigid an object is. All real-world objects, unless extremely hard, exhibit some form of squash and stretch.The classic example is the bouncing ball. The ball squashes as it hits the ground, then stretches on its way up and then back down. When an object squashes along one axis (direction), it automatically expands along the other two. It is up to you, as the animator, to ensure that any deformation along on axis is offset be an opposite deformation along other axes maintaining a constant volume.Consider the way a pillow changes shape as it's tossed across the room. The shape deforms, but does the volume of the pillow change? No matter how contorted the pillow becomes, it still maintains the same weight and amount of stuffing.
Overlapping action
Overlapping action implies that not everything happens at the same time. Take the example of moving a character's arm from a position of rest to that of picking up a set of keys on a table. A common mistake would be to advance a few frames from the at-rest position, then move all of the arm elements (objects) to the final position. This technique would result in a very lifeless motion (because everything starts and stops moving at the same time). The proper sequence requires that the upper arm begins to rise first. Then the forearm pivots out, followed by the wrist bending back. Finally, the fingers curl around the keys. Each of these motions begins before the preceding motion is complete, providing the realistic overlap that your viewer expects. In other words, the motion of the arm rotating upward is overlapped by the wrist bending back.
Follow-Through is a companion to the overlapping action. An action almost never comes to a complete and sudden stop. Instead, inertia carries the object beyond the termination point, often causing the object to slowly reverse direction and settle back to the intended stop location. A golfer's swing provides an ideal example of a follow-through. Once the ball is struck, the club (and golfer) follow through the point of contact to complete the swing. What about a pencil that drops to the ground? When it hits, does it stop dead in its tracks? Or, does it bounce around a little, then rolls to a stop? Two cars collide in the middle of an intersection. Do they hit and stick? No, recoil occurs, causing them to reverse direction. Again, an action almost never comes to a complete and sudden stop.
Staging
The concept behind Staging is that objects (still or animated) should be positioned in a way that they are quickly detected and are easily understood. A common mistake involves placing an object or action where it can't be noticed or in front of a more interesting object that divides the audience's attention. If your audience can't detect the action that you want them to notice, was your staging poor?Think of this situation. Your scene involves two characters sitting at a table talking to each other. You want your audience to view their conversation by positioning your camera behind one of the characters, looking over their shoulder. Do you think the shot is staged well if part of the character's head partially blocks the face of the other character? Or, would it be better to move the camera a little more to the side so you see both characters clearly. Which of the two would represent better staging? Obviously, the second.Try to visualize the primary objects in your scene as silhouettes. If an action occurs within the silhouette of an object, it is hard to detect. If you move the action to one side, where it's not masked by another object, it stands out much better. If you view your scene in silhouette and can't easily discern what's happening, consider using either a better viewing angle or possibly moving your scene objects so they can be more easily understood.
Exaggeration
Exaggeration is used to accentuate an action or idea. You often must exaggerate a motion or effect to ensure that the audience catches it. Exaggeration works in conjunction with anticipation and staging to direct the audience's attention to the action that you want them to see. Anticipation sets up the action, staging ensures that the action occurs where it can be seen, and exaggeration makes sure the action is not so subtle that the audience fails to notice it.Use of exaggeration shouldn't detract from the scene, but rather enhance reality by making sure the audience catches what is happening. Remember the Big Bad Wolf's exaggerated Mannerisms in attempting to blow down the Three Little Pig's house? The exaggerated size of his chest implied that nothing would withstand the hurricane-like force of his breath.Be careful on just how much exaggeration you use when working on human characters. Most people are very aware of how their body moves. Because of that, they are less forgiving of exaggeration of movement that goes to far beyond what is really possible.
Secondary Action
Secondary Action is any action that results directly from another action. Secondary actions heighten interest and add realistic complexity to an animation. They should always remain subordinate (not as important) to the primary action. They should not conflict, become more interesting or in any way dominate your primary point of interest. If the audience is paying too much attention to the secondary actions, they're missing the most important element (primary action) of your shot.It is sometimes easy to forget about secondary actions because we take such 'side effects' for granted in real life. Think of the basketball shot that hits the backboard rim. As an animator, you did a great job with the ball's shape as it hits the rim. But what about the effect the ball had on the rim itself? Did the rim wobble back and forth a little after the ball hit it? The rim wobbling is the secondary action; the result from another action (the ball hitting it).
Weight
Weight transfer is essential for realistic motion. Watch an elephant or rhinoceros walk through its surroundings. You can actually see (and almost feel) its weight shift from one portion of its body to another. Does a young kitten move the same way? Does a bowling ball bounce like a beach ball? Imagine how unbelievable a feather would appear if, when dropped, it shot straight down to the ground. Instead it sways from one side to another as it descends; its motion provides a clue as to its ratio of mass to surface area, and the resistance of the air.
Balance
With the exception of falling, the body is almost always in balance. If you extend your right arm, your left arm, shoulder and torso all pivot and move back. Few people stand perfectly straight. Think of what position other body parts should be in when one body part moves or changes location.Interesting Note: Walking and running are special cases of falling. When you walk, you constantly cycle through a process of falling forward, restoring balance and falling forward again. Running works the same way except that you spend most of your time falling forward.
Curved Motion
No straight lines exist in nature. This statement also applies to natural motion. Watch a person as they swing their arm up in a handshake. Does the arm simply swing straight up? Usually the arm not only swings up, but also swings out from the side and back in again. This subtle motion makes all the difference between an unnatural, robotic move and something that appears life-like.In contrast, a motion by an intentionally inanimate object should follow Newton's laws, i.e. move in a straight line until it is affected by a force. This provides the necessary contrast that differentiates it from a "sentient" object.