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20-05-2005, 12:45 AM

<center>
<center>Principles of traditional animation
 applied to the computer
</center>
John Lasseter Pixar San Rafael, California
<pre>[From ACM Computer Graphics, Volume 21, No. 4, July 1987]</pre></center>

<table width="504">
<t><tr><td>
"There is no particular mystery in animation...
it's really very simple, and like anything that is simple, it is about the hardest thing in the
world to do."</td></tr></t>
</table>

Bill Tytla at the Walt Disney Studio, June 28, 1937 [14] 

ABSTRACT
This paper describes the basic principles of traditional 2D hand drawn animation and their
application to 3D computer animation. After describing how these principles evolved, the
individual principles are detailed addressing their meanings in 2D hand drawn animation and
their application to 3D computer animation. This should demonstrate the importance of these
principles to quality 3D computer animation.

CR Categories and Subject Descriptors:
I.3.6 Computer Graphics: Methodology and Techniques -
Interaction techniques;
I.3.7 Computer Graphics: Three dimensional Graphics and Realism -
Animation;
J.5 Computer Applications: Arts and Humanities - Arts, fine and performing.
General Terms: Design, Human Factors.
Additional Keywords and Phrases: Animation Principles, Keyframe Animation, Squash and Stretch,
Luxo Jr.

1. INTRODUCTION

Early research in computer animation developed 2D animation techniques based on traditional
animation. [7] Techniques such as storyboarding [11], keyframe animation, [4,5] inbetweening,
[16,22] scan/paint, and multiplane backgrounds [17] attempted to apply the cel animation process
to the computer. As 3D computer animation research matured, more resources were devoted to image
rendering than to animation. Because 3D computer animation uses 3D models instead of 2D
drawings, fewer techniques from traditional animation were applied. Early 3D animation systems
were script based [6], followed by a few spline-interpolated keyframe systems. [22] But these
systems were developed by companies for internal use, and so very few traditionally trained
animators found their way into 3D computer animation.

The last two years have seen the appearance of reliable, user friendly, keyframe animation
systems from such companies as Wavefront Technologies Inc., [29] Abel Research (RIP), [1]
Vertigo Systems Inc., [28] Symbolics Inc., [25] and others. These systems will enable people to
produce more high quality computer animation. Unfortunately, these systems will also enable
people to produce more bad computer animation.

Much of this bad animation will be due to unfamiliarity with the fundamental principles that
have been used for hand drawn character animation for over 50 years. Understanding these
principles should also be important to the designers of the systems used by these animators.

In this paper, I will explain the fundamental principles of traditional animation and how they
apply to 3D keyframe computer animation.

2. PRINCIPLES OF ANIMATION

Between the late 1920's and the late 1930's animation grew from a novelty to an art form at the
Walt Disney Studios. With every picture, actions became more convincing, and characters were
emerging as true personalities. Audiences were enthusiastic and many of the animators were
satisfied, however it was clear to Walt Disney that the level of animation and existing
characters were not adequate to pursue new story lines-- characters were limited to certain
types of action and audience acceptance notwithstanding, they were not appealing to the eye. It
was apparent to Walt Disney that no one could successfully animate a humanized figure or a
life-like animal; a new drawing approach was necessary to improve the level of animation
exemplified by the "Three Little Pigs".

<center>
<img src="http://www.geocities.com/stephenkmann/anm/images/animated-bw-luxo.gif" height="64" width="64" border="0">
Figure 1. Luxo Jr.'s hop with overlapping action on cord.
(The original paper had you "Flip pages from last page of paper
to front." The top figures were frames 1-5, the bottom were frames 6-10)
</center>
Disney set up drawing classes for his animators at the Chouinard Art Institute in Los Angeles
under Instructor Don Graham. When the classes were started, most of the animators were drawing
using the old cartoon formula of standardized shapes, sizes, actions and gestures, with little
or no reference to nature. Out of these classes grew a way of drawing moving human figures and
animals. The students studied models in motion as well as live action film, playing certain
actions over and over. The analysis of action became important to the development of animation.

Some of the animators began to apply the lessons of these classes to production animation, which
became more sophisticated and realistic. The animators continually searched for better ways to
communicate to one another the ideas learned from these lessons. Gradually, procedures were
isolated and named, analyzed and perfected, and new artists were taught these practices as rules
of the trade. They became the fundamental principles of traditional animation:<table width="504">

<t><tr>
<td>
<ol start="1" ="1"><li>Squash and Stretch - Defining the rigidity & mass of an object by distorting its shape during an action. 

</li><li>Timing - Spacing actions to define the weight & size of objects & the personality of characters. 

</li><li>Anticipation - The preparation for an action. 

</li><li>Staging - Presenting an idea so that it is unmistakably clear. 

</li><li>Follow Through & Overlapping Action - The termination of an action & establishing its relationship to the next action. 

</li><li>Straight Ahead Action & Pose-To-Pose Action - The two contrasting approaches to the creation of movement. 

</li><li>Slow In and Out - The spacing of in-between frames to achieve subtlety of timing & movements. 

</li><li>Arcs - The visual path of action for natural movement. 

</li><li>Exaggeration - Accentuating the essence of an idea via the design & the action. 

</li><li>Secondary Action - The Action of an object resulting from another action. 

</li><li>Appeal - Creating a design or an action that the audience enjoys watching.
</li></ol></td></tr></t></table>
The application of some of these principles mean the same regardless of the medium of animation.
2D hand drawn animation deals with a sequence of two dimensional drawings that simulate motion.
3D computer animation involves creating a three dimensional model in the computer. Motion is
achieved by setting keyframe poses and having the computer generate the inbetween frames.
Timing, anticipation, staging, follow through, overlap, exaggeration, and secondary action apply
in the same way for both types of animation. While the meanings of squash and stretch, slow in
and out, arcs, appeal, straight ahead action, and pose-to-pose action remain the same, their
application changes due to the difference in medium. 
 
<pre>2.1 SQUASH AND STRETCH The most important principle is called Squash and Stretch. When an object is moved, the movement emphasizes any rigidity in the object. In real life, only the most rigid shapes (such as chairs, dishes and pans) remain so during motion. Anything composed of living flesh, no matter how bony, will show considerable movement in its shape during an action. For example, when a bent arm with swelling biceps straightens out, only the long sinews are apparent. A face, whether chewing, smiling, talking, or just showing a change of expression, is alive with changing shapes in the cheeks, the lips, and the eyes. 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. The most important rule to squash and stretch is that, no matter how squashed or stretched out a particular object gets, its volume remains constant. If an object squashed down without its sides stretching, it would appear to shrink; if it stretched up without is sides squeezing in it would appear to grow. Consider the shape and volume of a half filled flour sack when dropped on the floor, it squashed out to its fullest shape. If picked up by the top corners, it stretched out to its longest shape. It never changes volume. The standard animation test for all beginners is drawing a bouncing ball. The assignment is to represent the ball by a simple circle, and then have it drop, hit the ground, and bounce back up into the air. A simple test, but it teaches the basic mechanics of animating a scene, introducing timing as well as squash and stretch. If the bottom drawing is flattened, it gives the appearance of bouncing. Elongating the drawings before and after the bounce increases the sense of speed, makes it easier to follow and gives more snap to the action. (fig. 2) <center> <img src="http://www.geocities.com/stephenkmann/anm/images/figure2.gif" height="115" width="224" border="0"> Figure 2. Squash & stretch in bouncing ball </center> Squash and stretch also defines the rigidity of the material making up an object. When an object is squashed flat and stretches out drastically, it gives the sense that the object is made out of a soft, pliable material and vice versa. When the parts of an object are of different materials, they should respond differently: flexible parts should squash more and rigid parts less. An object need not deform in order to squash and stretch. For instance, a hinged object like Luxo Jr. (from the film Luxo Jr.) squashes by folding over on itself, and stretches by extending out fully. (fig. 3) <center> <img src="http://www.geocities.com/stephenkmann/anm/images/figure3.gif" height="114" width="222" border="0"> Figure 3. Squash & stretch in Luxo Jr.'s hop </center> Squash and stretch is very important in facial animation, not only for showing the flexibility of the flesh and muscle, but also for showing the relationship of between the parts of the face. When a face smiles broadly, the corners of the mouth push up into the cheeks. The cheeks squash and push up into the eyes, making the eyes squint, which brings down the eyebrows and stretches the forehead. When the face adopts a surprised expression, the mouth opens, stretching down the cheeks. The wide open eyes push the eyebrows up, squashing and wrinkling the forehead. Another use of squash and stretch is to help relieve the disturbing effect of strobing that happens with very fast motion because sequential positions of an object become spaced far apart. When the action is slow enough, the object's positions overlap, and the eye smoothes the motion out. (figure 4a) However, as the speed of the action increases, so does the distance between positions. When the distance becomes far enough that the object does not overlap from frame to frame, the eye then begins to perceive separate images. (figure 1b) Accurate motion blur is the most realistic solution to this problem of strobing, [8,9] but when motion blur is not available, squash and stretch is an alternative: the object should be stretched enough so that its positions do overlap from frame to frame (or nearly so), and the eye will smooth the action out again. (figure 4c) <center> <img src="http://www.geocities.com/stephenkmann/anm/images/figure4a.gif" height="48" width="130" border="0"> FIGURE 4a. In slow action, an object's position overlaps from frame to frame which gives the action a smooth appearance to the eye <img src="http://www.geocities.com/stephenkmann/anm/images/figure4b.gif" height="51" width="216" border="0"> FIGURE 4b. Strobing occurs in a faster action when the object's positions do not overlap and the eye perceives separate images <img src="http://www.geocities.com/stephenkmann/anm/images/figure4c.gif" height="48" width="231" border="0"> FIGURE 4c. Stretching the object so that it's positions overlap again will relieve the strobing effect </center> In 3D keyframe computer animation, the scale transformation can be used for squash and stretch. When scaling up in Z, the object should be scaled down in X and Y to keep the volume the same. Since the direction of the stretch should be along the path of action, a rotational transformation may be required to align the object along an appropriate axis. ------------------------------------------------------------ --------------------------------------------------------- 2.2 TIMING 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 behind the action will read to an audience. It reflects the weight and size of an object, and can even carry emotional meaning. Proper timing is critical to making ideas readable. It is important to spend enough time (but no more) preparing the audience for: the anticipation of an action; the action itself; and the reaction to the action. If too much time is spent on any of these, the audience's attention will wander. If too Little time is spent. the movement may be finished before the audience notices it, thus wasting the idea. The faster the movement, the more important it is to make sure the audience can follow what is happening. The action must not be so fast that the audience cannot read it and understand the meaning of it. [30] More than any other principle, timing defines the weight of an object. Two objects, identical in size and shape, can appear to be two vastly different weights by manipulating timing alone. The heavier an object is, the greater its mass, and the more force is required to change its motion. A heavy body is slower to accelerate and decelerate than a light one. It takes a large force to get a cannonball moving, but once moving, it tends to keep moving a the same speed and requires some force to stop it. When dealing with heavy objects, one must allow plenty of time and force to start, stop or change their movements, in order to make their weight look convincing. [30] Light objects have much less resistance to change of movement and so need much less time to start moving. The flick of a finger is enough to make a balloon accelerate quickly away. When moving, it has little momentum and even the friction of the air quickly slows it up. [30] Timing can also contribute greatly to the feeling of size or scale of m object or character. A giant has much more weight, more mass, more inertia than a normal man; therefore he moves more slowly. Like the cannonball, he takes more time to get started and, once moving, takes more time to stop. Any changes of movement take place more slowly. Conversely, a tiny character has less inertia than normal, so his movements tend to be quicker. [30] The way an object behaves on the screen, the effect of weight that it gives, depend entirely on the spacing of the poses and not on the poses themselves. No matter how well rendered a cannonball may be, it does not look like a cannonball if it does not behave like one when animated. The same applies to any object or character. [30] The emotional state of a character can also be defined more by its movement than by its appearance, and the varying speed of those movements indicates whether the character is lethargic, excited, nervous or relaxed. Thomas and Johnston [26] describe how changing the timing of an action gives it new meaning: Just two drawings of a head, the first showing it leaning toward the right shoulder and the second with it over on the left and its chin slightly raised, can be made to communicate a multitude of ideas, depending entirely on the timing used. Each in-between drawing added between these two extremes gives a new meaning to the action. NO inbetweens.....The Character has been hit by a tremendous force. His head is nearly snapped off. ONE inbetween.....The Character has been hit by a brick, rolling pin, frying pan. TWO inbetweens.....The Character has a nervous tic, a muscle spasm, an uncontrollable twitch. THREE inbetweens.....The Character is dodging a brick, rolling pin, frying pan. FOUR inbetweens.....The Character is giving a crisp order, "Get going!" "Move it!" FIVE inbetweens.....The Character is more friendly, "Over here." "Come on-hurry!" SIX inbetweens.....The Character sees a good looking girl, or the sports car he has always wanted SEVEN inbetweens.....The Character tries to get a better look at something.
<!--
?CENTER??IMG SRC="images/figure1b.lj.gif"
WIDTH="153" HEIGHT="154"??/CENTER?-- border="0"> EIGHT inbetweens.....The Character searches for the peanut butter on the kitchen shelf. NINE inbetweens.....The Character appraises, considering thoughtfully. TEN inbetweens.....The Character stretches a sore muscle. </pre>
<center>

 <img src="http://www.geocities.com/stephenkmann/anm/images/figure5a.wb.gif" height="180" width="240" border="0"> 
 <img src="http://www.geocities.com/stephenkmann/anm/images/figure5b.wb.gif" height="180" width="240" border="0"> 
 <img src="http://www.geocities.com/stephenkmann/anm/images/figure5c.wb.gif" height="180" width="240" border="0"> 
 <img src="http://www.geocities.com/stephenkmann/anm/images/figure5d.wb.gif" height="180" width="240" border="0"> 
 Figure 5. Wally B.'s zip off shows use of squash and stretch, anticipation,
 follow through, overlapping action and secondary action.
</center>

------------------------------------------------------ ---------------------------------------- 
<pre> 2.3 ANTICIPATION An action occurs in three parts: the preparation for the action, the action proper, and the termination of the action. Anticipation is the preparation for the action; the latter two are discussed in the next sections. There are several facets to Anticipation. In one sense, it is the anatomical provision for an action. Since muscles in the body function through contraction, each must first be extended before it can contract. A foot must be pulled back before it can be swung forward to kick a ball. [12] Without anticipation many actions are abrupt, stiff and unnatural. Anticipation is also a device to catch the audience's eye, to prepare them for the next movement and lead them to especially before it actually occurs. Anticipation is often used to explain what the following action is going to be. Before a character reaches to grab an object, he first raises his arms as he stares at the article, broadcasting the fact that he is going to do something with that particular object. The anticipatory moves may not show why he is doing something, but there is no question about what he is going to do next. [26] Anticipation is also used to direct the attention of the audience to the right part of the screen al the right moment This is essential for preventing the audience from missing some vital action. In the very beginning of Luxo Jr., Dad is on screen alone looking offstage. He then reacts, anticipating something happening there. When Jr. does hop in. the audience is prepared for the action. The amount of anticipation used considerably affects the speed of the action which follows it If the audience expects something o happen, then it can be much faster without losing them. If they are not properly prepared for a very fast action, they may miss it completely; the anticipation must be made larger or the action slower. [30] In a slow action the anticipation is often minimized and the meaning carried in the action proper. [12] In one shot in The Adventures of Andr? and Wally B., Wally B. zips off to the right. The actual action of the zip off is only 3 or 4 frames long, but he anticipates the zip long enough for the audience to know exactly what is coming next. (figure 5) Anticipation can also emphasize heavy weight. As for a character picking up an object that is very heavy. An exaggerated anticipation, like bending way down before picking up the object, helps the momentum of the character to lift the heavy weight. Likewise for a fat character standing up from a seated position: he will bend his upper body forward, with his hands on the armrests of the chair, before pushing up with his arms and using the momentum of his body. ------------------------------------------------------------ --------------------------------------------------------- 2.4 STAGING Staging is the presentation of an idea so it is completely and unmistakably clear, this principle translates directly from 2D hand drawn animation. An action is staged so that it is understood; a personality is staged so that it is recognizable; an expression so that it can be seen: a mood so that it will affect the audience. [26] To stage an idea clearly, the audience's eye must be led to exactly where it needs to be al the right moment, so that they will not miss the idea. Staging, anticipation and timing are all integral to directing the eye. A well-timed anticipation will be wasted if it is not staged clearly. It is important, when staging an action. that only one idea be seen by the audience at a time. If a lot of action is happening at once, the eye does not know where to look and the main idea of the action will be "upstaged" and overlooked. The object of interest should contrast from the rest of the scene. In a still scene, the eye will be attracted to movement. In a very busy scene, the eye will be attracted to something that is still. Each idea or action must be staged in the strongest and the simplest way before going on to the next idea or action. The animator is saying. in effect, "Look at this, now look at this. and now look at this." [26] In Luxo Jr., it was very important that the audience was looking in the right place at the right time, because the story, acting and emotion was being put across with movement alone, in pantomime, and sometimes the movement was very subtle. If the audience missed an action, an emotion would be missed, and the story would suffer. So the action had to be paced so that only Dad or Jr. was doing an important action at any one time, never both. In the beginning of the film, Dad is on screen alone your eye was on him. But as soon as Jr. hops on-screen, he is moving faster than Dad. therefore the audience's eyes immediately goes to him and stays there. Most of the time Jr. was on-screen, Dad's actions were very subtle, so the attention of the audience was always on Jr. where most of the story was being told. If Dad's actions were important, Jr.'s actions were toned down and Dad's movements were emphasized and the attention of the audience would transfer to Dad. For example, when Jr. looks up to Dad after he's popped the ball and Dad shakes his head, all eyes are on him. Another idea developed in the early days at Disney was the importance of staging an action in silhouette. In those days, all the characters were black and white, With no gray values to soften the contrast or delineate a form. Bodies, arms and hands were all black, so there was no way to stage an action clearly except in silhouette. A hand in front of a chest would simply disappear. Out of this limitation, the animators realized that it is always better to show an action in silhouette. Charlie Chaplin maintained that if an actor knew his emotion thoroughly, he could show it in silhouette. [26] In The Adventures of Andr? and Wally B., Andr? awakes and sits up, then scratches his side. If he were to scratch his stomach instead of his side, the action would happen in front of his body and would be unclear what was happening. (figure 6) </pre>
<center>
<img src="http://www.geocities.com/stephenkmann/anm/images/figure6.wb.gif" height="180" width="240" border="0"> 
 FIGURE 6. Andr?'s scratch was staged to the side (in "silhouette") for
 clarity and because that is where his itch was.
</center>

 In Luxo Jr., all the action was animated with silhouette in mind. When Dad and Jr. come face to
 face for the first time, it is easy to see what is happening because it is staged to the side.
 If Jr. was in front of Dad looking up at him, it would be difficult to read. (figure 7) Jr.
 hopping on the ball would be confusing if the action was to happen with Jr. facing the camera
 Viewed from the side it is perfectly clear. (figure 8) 
---------------------------------------------------------- ------------------------------------- 
<pre> 2.5 FOLLOW THROUGH AND OVERLAPPING ACTION Just as the anticipation is the preparation of an action, follow through is the termination of an action. Actions very rarely come to a sudden and complete stop, but are generally carried past their termination point. For example, a hand, after releasing a thrown ball, continues past the actual point of release. In the movement of any object or figure, the actions of the parts are not simultaneous some part must initiate the move, like the engine of a train. This is called the lead. In walking, the action starts with the hips. As the hip swings forward, it sets a leg in motion. The hip "leads", the leg <center> <img src="http://www.geocities.com/stephenkmann/anm/images/figure7.lj.gif" height="152" width="240" border="0"> <img src="http://www.geocities.com/stephenkmann/anm/images/figure8.lj.gif" height="152" width="240" border="0"> FIGURES 7-8. In Luxo Jr., all action was staged to the side for clarity </center> "follows." As the hip twists, the torso follows, then the shoulder, the arm, the wrist, and finally the fingers. Although most large body actions start in the hips, the wrist will lead the fingers in a hand gesture, and the eyes will usually lead the head in an action. [12] Appendages or loose parts of a character or object will move at a slower speed and 'drag' behind the leading part of the figure. Then as the leading part of the figure slows to a stop. These appendages will continue to move and will take longer to settle down. As with squash and stretch, the object's mass is shown in the way the object slows down. The degree that the appendages drag behind and the time it takes for them to stop is directly proportional to their weight. The heavier they are the farther behind they drag and the longer they take to settle to a stop. Conversely, if they are lighter, they will drag less and stop more quickly.
<!--
?IMG SRC="images/figure1c.lj.gif" WIDTH="163"
HEIGHT="160"?-- border="0"> In The Adventures of Andr? and Wally B., this principle was used extensively on Wally B.'s feet, antennae and stinger. They all dragged behind his head and body. and continued to move well after the body had stopped. To convey that these loose appendages were made of different materials and different masses, the rate of the follow through was different for each type. His antennae were fairly light, so they dragged behind just slightly. His stinger was like stainless steel, so it dragged behind the action more than the antennae. And his feet were heavy and very flexible, as though they were water balloons; therefore, they always followed far behind the main action. With a lot of squash and stretch. In the zip off illustrated above (figure 5), the action of Wally B.'s body was so fast and the feet weighed so much that they dragged far behind. They were even left on screen frames after the body had disappeared. Often, slight variations are added to the timing and speed of the loose parts of objects. This overlapping action makes the object seem natural, the action more interesting. In Wally's zip off (figure 5), his feet zipped off, one after the other, about one or two frames apart. The action was so fast that it was difficult to see each foot going off separately, but it made the action as a whole more interesting. Perhaps more important, overlapping is critical to conveying main ideas of the story. An action should never be brought to a complete stop before starting another action, and the second action should overlap the first. Overlapping maintains a continual flow and continuity between whole phrases of actions. Walt Disney once explained overlapping this way, "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 the had never given it a thought until after completing the first action. When a character knows what his 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. For example, the mind thinks, ' I'll close the door - lock it then I'm going to undress and go to bed.' Well, you walk over to the door before the walk is finished you're reaching for the door - before the door is closed you reach for the key - before the door is locked you're turning away - while you're walking away you undo your tie - and before you reach the bureau you have your tie off. In other words, before you know it you're undressed and you've done it in one thought, "I'm going to bed." [12] ------------------------------------------------------------ --------------------------------------------------------- -- 2.6 STRAIGHT AHEAD ACTION AND POSE-TO-POSE ACTION (KEYFRAMES) There are two main approaches to hand drawn animation. The first is known as straight ahead action because the animator literally works straight ahead from his first drawing in the scene. He knows where the scene fits in the story and the business it has to include. He does one drawing after another, getting new ideas as he goes along, until he reaches the end of the scene. This process usually produces drawings and action that have a fresh and slightly zany look. because the whole process was kept very creative. Straight ahead action is used for wild, scrambling actions where spontaneity is important. The second approach is called pose to-pose. Here the animator plans his actions, figures out just what drawings will be needed to animate the business, makes the drawings concentrating on the poses, relates them to each other in size and action, and then draws the inbetweens. Pose-to-pose is used for animation that requires good acting, where the poses and timing are all important. The pose-to-pose technique applies to keyframe computer animation with timing and pose control of extremes and inbetweens. The difficulty in controlling the inbetweens makes it incorrect to approach keyframe computer animation exactly as one would pose-to-pose hand drawn animation. In working with a complex model, creating a complete pose at a time would make the inbetweens too unpredictable. The path of action will in general be incorrect and objects will intersect one another. The result is much time-consuming reworking of inbetweens. There is a much better approach in the context of a hierarchical modeling system, which works "layer by layer" down the hierarchy. Instead of animating one complete pose to another, one transformation is animated at a time, starting with the trunk of the hierarchical tree structure, working transformation by transformation down the branches to the end. Fewer extremes are used not all translates, rotates and scales have extremes on the same frames; some have many extremes and others very few. With fewer extremes, the importance of the inbetweens increases. Tension and direction controls on the interpolating splines are helpful in controlling the spacing of the inbetween and to achieve slow in and out. [16] (See Slow In and Out) This layer approach to animation shares many important elements with the pose-to-pose technique in hand drawn animation. Planning the animation out in advance, as in pose-to-pose, becomes even more important The action must be well thought out, the timing and poses planned so that even in the early layers, the poses and actions arc clear. The Adventures of Andr? and Wally B and Luxo Jr. were both animated using a keyframe animation system called Md (Motion Doctor). [19] Luxo Jr. was animated using this layered approach to the keyframes. Jr.'s hop (figure 1) was animated by first setting the keyframes for his forward movement only: two keyframes were set for the X translation, the first where the hop starts and the second where he lands. This defined the timing of his hop. The height of his hop was then defined by setting a keyframe in the Z translation (Z being up in this case). The next step, animating the rotation of Jr.'s arms, was important because the arms define the anticipation, squash and stretch, and follow through of the action. Keyframes were set for just about every frame, rotating the arms together before the hop for the anticipation, then immediately far apart for the stretch of the jump. The arms were rotated together again at the top of the arc where the action slows slightly, then rotated far apart, stretching to anticipate the landing. To indicate the shock of the landing, the arms were rotated quickly together two frames after the base lands on the floor. This is the follow through of the action. His base and shade were animated in the next two steps. Like the arms, many keyframes were set to define the rotation of the base and shade because their movement was important for anticipation and follow through. ------------------------------------------------------------ --------------------------------------------------------- -- 2.7 SLOW IN AND OUT Slow in and out deals with the spacing of the inbetween drawings between the extreme poses. Mathematically, the term refers to second- and third-order continuity of motion. In early animation, the action was limited to mainly fast and slow moves, the spacing from one drawing to the next fairly even. But when the poses of pose-to-pose animation became more expressive, animators wanted the audience to see them. They found that by grouping the inbetweens closer to each extreme, with only one fleeting drawing halfway between, they could achieve a very spirited result, with the character zipping from one attitude to another. "Slowing out" of one pose, then "slowing in" to the next pose simply refers to the timing of the inbetweens. The animator indicates the placement of the inbetweens, the slow in or slow out, with a "timing chart" drawn on the side of the drawing. This tells himself, or his assistant who will be doing the inbetweens later, how he wanted the timing to be and where he wanted the inbetween drawings placed. (figure 9) </pre>
<center>
<img src="http://www.geocities.com/stephenkmann/anm/images/figure9.tm.gif" height="104" width="193" border="0"> 
 FIGURE 9. Timing chart for ball bounce
</center>

 In most 3D keyframe computer animation systems, the inbetweening is done automatically using
 spline interpolation. Slow in and slow out is achieved by adjusting the tension, direction or
 bias, and continuity of the splines. [16] This works well to give the affect of slow in and out,
 but a graphical representation of the spline is required to see the effect of tension,
 direction, and continuity have on its shape.

 With this type of spline interpolation, a common problem is the spline overshooting at extremes
 when there is a large change in value between them, especially over a small number of frames.
 This also happens when the direction control of an extreme is adjusted. The danger is that,
 depending on the variable the spline controls (translate, rotate, or scale), the value will
 shoot in the wrong direction just before (or just after) the large change in value. Sometimes
 this effect works out well when it occurs just before a large movement it may appear to be an
 anticipation. However, more often than not, it gives an undesirable effect.

 In Luxo Jr., there was an example of this problem of overshooting splines, Jr.'s base was very
 heavy and when he hopped, we wanted the base to start stationary, then pop up in the air from
 the momentum of his jump, arc over, then land with a thud, suddenly stationary again. For the up
 translation, there were three keyframes, the two stationary positions and the highest point of
 his jump. The spline software forced continuity, so that his base would move down under the
 surface of the floor just before and after the jump. (figure 10a) The solution was to put two
 new extremes, equal to the two stationary extremes, on the frames just before and just after the
 extremes. This "locked" down the spline, so that the up translation stayed the same value,
 popped up in the air, landed and then stayed the same value again. This gave the desired feeling
 of weight to his little base. (figure 10b)

 The same solution can be achieved by breaking the spline using its continuity parameter [16] at
 the two stationary extremes. This solution requires a graphical display of the spline so that
 the correct shape can be achieved.

 

<center>
<img src="http://www.geocities.com/stephenkmann/anm/images/figure10a.gif" height="118" width="256" border="0"> 
 FIGURE 10a This spline controls the Z (up) translation of Luxo Jr. Dips in the
 spline cause him to intersect the floor

 <img src="http://www.geocities.com/stephenkmann/anm/images/figure10b.gif" height="115" width="257" border="0"> 
 FIGURE 10b. Two extra extremes are added to the spline which removes the dips and
 prevents Jr. from going into the basement 
------------------------------------------------------------ --------------------------------------------------------- ---- 

<div style="text-align: left;">
<pre>2.8 ARCS The visual path of action from one extreme to another is always described by an arc. Arcs in nature are the most economical routes by which a form can move from one position to another. In animation. such arcs are used extensively, for they make animation much smoother and less stiff than a straight line for the path of action. In certain cases, an arc may resolve itself into a straight path, as for a falling object. but usually, even in straight line action, the object rotates. [12] In most 3D keyframe computer animation systems, the path of action from one extreme to another is controlled by the same spline that controls the timing (slow in and out) of the inbetween values. This may simplify computing the inbetweens but it has unfortunate effects. When a motion is slow, with many inbetweens, the arc of the path of action is curved, as desired. But when the action is fast, the arc flattens out the faster the action, the flatter the arc. Sometimes this is desirable. but more often, the path of even a fast motion should be curved or arced. Straight inbetweens can completely kill the essence of an action. The spline that defines the path of action should be separate from the spline that defines the Liming or spacing of the inbetweens for several reasons: so that the arc of a fast action doesn't flatten out; so that you can adjust the timing of the inbetweens without effecting the path of action; so that you can use different splines to define the path of action (where a B-spline is appropriate for its smoothness) and the timing (a Catmull - Rom spline so you can adjust it's tension and direction controls to get slow in and out). This technique is not common, but research is being done in this area. [15] ------------------------------------------------------------ --------------------------------------------------------- - 2.9 EXAGGERATION The meaning of exaggeration is, in general, obvious. However, the principle of exaggeration in animation does not mean arbitrarily distorting shapes or objects or making an action more violent or unrealistic. The animator must go to the heart of anything or any idea and develop its essence, 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; wild, make him frantic. A scene has many components to it the design, the shape of the objects, the action, the emotion, the color, the sound. Exaggeration can work with any component but not in isolation. The exaggeration of the various components should be balanced. If just one thing is exaggerated in an otherwise lifelike scene, it will stick out and seem unrealistic.
<!--
?IMG SRC="images/figure1d.lj.gif" WIDTH="164"
HEIGHT="148"?-- border="0"> </pre>
<center>

 <img src="http://www.geocities.com/stephenkmann/anm/images/figure11a.gif" height="145" width="194" border="0"> 
 FIGURE 11. Varying the scale of different parts of Dad created the child-like
 proportions of Luxo Jr.

 <img src="http://www.geocities.com/stephenkmann/anm/images/figure12a.gif" height="180" width="240" border="0"> 
 <img src="http://www.geocities.com/stephenkmann/anm/images/figure12b.gif" height="180" width="240" border="0"> 
 FIGURE 12. Andr?'s yawn was made more interesting by not duplicating
 the poses and the action from one side of his body to the other
</center>

 However, exaggerating everything in a scene can be equally unrealistic to an audience. Some
 elements must be based in nature, with others exaggerated unnaturally. If there is an element
 that the audience can recognize, something that seems natural to them, that becomes the ground
 for comparison of the exaggeration of the other elements, and the whole scene remains very
 realistic to them.

 In Luxo Jr., all the components of the scene some naturalistic, some exaggerated, worked
 together to make it believable and realistic. The design of the lamps was based on the real Luxo
 lamp, but certain parts were exaggerated Jr.'s proportions were exaggerated to give the feeling
 of a child. (See Appeal)

 The movement had the sense of natural physics, yet almost every motion and action was
 exaggerated to accentuate it: when Jr. hit the ball, he really whacked it. When he jumped up for
 a hop, his whole body movement was exaggerated to give the feeling of realistic weight to his
 base. When he landed after a hop, the impact was shown in the exaggeration of his body
 movements. On the soundtrack, the lamp sounds were recorded from a real Luxo lamp, then
 exaggerated sounds were added to accentuate certain actions. [23] The ironic effects of all this
 exaggeration was to make the film more realistic, while making it entertaining. 
---------------------------------------------------------- ------------------------------------- - 
<pre>2.10 SECONDARY ACTION A secondary action is an action that results directly from another action. Secondary actions are important in heightening interest and adding a realistic complexity to the animation. A secondary actions is always kept subordinate to the primary action If it conflicts, becomes more interesting, or dominates in any way, it is either the wrong choice or is staged improperly. [26] Wally B 's feet dragging behind the main action of his body is a secondary action because he movement of the feet is a direct result of the movement of the body. (figure 5) The rippling movement of Luxo Jr.'s cord results directly from the hopping action of his base. (figure 1) The facial expression of a character will sometimes be a secondary action. When the main idea of an action is being told in the movement of the body, the facial expression become subordinate to the main idea. If this expression is going to animate or change, the danger is not that the expression will dominate the scene, but that it will never be seen. The change must come before, or after, the move. A change in the middle of a major move will go unnoticed, and value intended will be lost. It must also be staged to be obvious, though secondary. [26] ------------------------------------------------------------ --------------------------------------------------------- ----- 2.11 APPEAL The word appeal is often misrepresented to suggest cuddly bunnies and soft kittens. It doesn't: it means anything that a person likes to see: a quality of charm, pleasing design, simplicity, communication, or magnetism. Your eye is drawn to the figure or object that has appeal, and, once there, it is held while you appreciate the object. 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. Where the live action actor has charisma the animated character has appeal. [261 The appeal in Luxo Jr. was achieved in different ways. In designing the characters, the feeling of a baby lamp and a grown up lamp was very important. The effect was achieved using exaggeration in proportion, in the same way a puppy is proportioned very differently than an adult dog, or a human baby is different from an adult. The light bulb is the same size on Jr., while the shade is smaller. The springs and support rods are the same diameter as Dad's, yet they are much shorter. (figure 11) 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 gives the pose a stiff, wooden, unappealing quality. If each part of the body varies in some way from its corresponding part, the character will look more natural and more appealing. Likewise one side of a face should never mirror the other. In The Adventures of Andr? and Wally B., Andr? wakes up and yawns. The yawn is more appealing because the poses and actions are not duplicate from one site of his body to the other. His feet rotate with a slight difference, the head rotates to one side, the upper part of his body rotates to the right and tilts, which raises his right arm higher than his left. When he stretches his arms, the right arm moves out first, followed by the left, and the actions overlap. (figure 12)
 ------------------------------------------------------------ ------------ 3. PERSONALITY This final section discusses the underlying goal of all the principles discussed earlier. Personality in character animation is not a principle unto itself, but the intelligent application of all of the principles of animation. When character animation is successful and the audience is thoroughly entertained, it is because the characters and the story have become more important and apparent than the technique that went into the animation. Whether drawn by hand or computer, the success of character animation lies in the personality of the characters. In character animation, all actions and movements of a character are the result of its thought processes. "The thinking animation character becomes a character." [12] Without a thought process, the actions of a character are just a series of unrelated motions. With a thought process to connect them, the actions bring a character to life. In order to get a thought process into an animation, it is critical to have the personality of a character clearly in mind at the outset, so that it makes sense to ask at any moment, "What mood is the character in. How would he do this action?" One character would not do a particular action the same way in two different emotional states. An example of this, in Luxo Jr., is the action of Jr. hopping. When he is chasing the ball, he is very excited, happy, all his thoughts on the ball. His hops are fast, his head up looking at the ball, with very little time on the ground between hops because he can't wait to get to the ball. After he pops the ball, however, his hop changes drastically, reflecting his sadness that the object of all of his thoughts and energy just a moment ago is now dead. As he hops off, each hop is slower, with much more time on the ground between hops, his head down. Before, he had a direction and purpose to his hop. Now he is just hopping off to nowhere. No two characters would do the same action in the same way. For example, in Luxo Jr., both Dad and Jr. bat the ball with their heads. Yet Dad, who is bigger and older, leans over the ball and uses only his shade to bat it. Jr., however, who is smaller, younger, and full of excited energy, whacks the ball with his shade, putting his whole body unto it. When defining the character, it is important to makes the personality distinct, and at the same time have characteristics that are familiar to the audience. If the actions of a character ring true, the audience will be able to relate to the character, and he will

dynafx

20-05-2005, 12:46 AM

<h1 align="center"><a name="top"></a>Tricks to Animating Characters with a Computer</h1>

John Lasseter 
Pixar

Reference: These notes come from Course 1 at SIGGRAPH 94, "Animation
Tricks".

<img src="http://www.siggraph.org/education/materials/HyperGraph/icons/redball.gif" height="14" width="14" border="0"><a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#abstract" target="_blank">Abstract</a>

<img src="http://www.siggraph.org/education/materials/HyperGraph/icons/redball.gif" height="14" width="14" border="0"> <a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#keyframes" target="_blank">Keyframes</a>

<img src="http://www.siggraph.org/education/materials/HyperGraph/icons/redball.gif" height="14" width="14" border="0"> <a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#2dvs3d" target="_blank">2-D VS. 3-D </a>

<img src="http://www.siggraph.org/education/materials/HyperGraph/icons/redball.gif" height="14" width="14" border="0"> <a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#weight&size" target="_blank">WEIGHT & SIZE </a>

<img src="http://www.siggraph.org/education/materials/HyperGraph/icons/redball.gif" height="14" width="14" border="0"> <a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#thinking%20character" target="_blank">THE THINKING
CHARACTER </a>

<img src="http://www.siggraph.org/education/materials/HyperGraph/icons/redball.gif" height="14" width="14" border="0"> <a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#moving%20holds" target="_blank">MOVING HOLDS </a>

<img src="http://www.siggraph.org/education/materials/HyperGraph/icons/redball.gif" height="14" width="14" border="0"> <a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#emotion" target="_blank">EMOTION </a>

<img src="http://www.siggraph.org/education/materials/HyperGraph/icons/redball.gif" height="14" width="14" border="0"> <a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#readability%20of%20actions" target="_blank">READABILITY OF
ACTIONS </a>

<img src="http://www.siggraph.org/education/materials/HyperGraph/icons/redball.gif" height="14" width="14" border="0"> <a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#story%20trick" target="_blank">A STORY TRICK </a>

<img src="http://www.siggraph.org/education/materials/HyperGraph/icons/redball.gif" height="14" width="14" border="0"> <a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#ask%20why" target="_blank">ASK WHY </a>

<img src="http://www.siggraph.org/education/materials/HyperGraph/icons/redball.gif" height="14" width="14" border="0"> <a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#references" target="_blank">REFERENCES</a>

<img src="http://www.siggraph.org/education/materials/HyperGraph/icons/redball.gif" height="14" width="14" border="0"> <a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/ollie_johnston.htm" target="_blank">Animation Notes from
Ollie Johnston</a>

<hr>

<h2><a name="abstract"></a>ABSTRACT </h2>

When I presented the first animation I had created with a
computer, "The Aventures of Andr? and Wally B.," at Siggraph ?84, a number
of people asked me what cool new software I had used to achieve such believable
characters. I explained to them that the software was a keyframe animation system, not
much different in theory than other systems that were around then. What was different was
that I was using basic animation principles that I had learned as a traditional animator.
It was not the software that gave life to the characters, it was these principles of
animation, these tricks of the trade that animators had developed over fifty years ago. I
was surprised at how few people in the computer animation community were aware of these
principles.

Traditional animation is basically one trick after another.
Whatever it takes to get it working right on the screen is fair game. It should be the
same in computer animation. At Pixar, we constantly use tricks, old and new, to get what
we need on the screen. In this talk, I will give away a few trade secrets that will be
useful to anyone attemping to animate characters with computers, regardless of the
software they are using.

<a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#top" target="_blank">Top</a>

<hr style="height: 2px;">

<h2><a name="keys"></a>KEYFRAMES </h2>

Most commercially available computer animation systems are
based on animating with keyframes. At first, this seems like the same thing as keyframes
in traditional hand-drawn animation, but it is slightly different, and therefore, you
should approach your animation differently. In hand-drawn animation, you work on the basic
poses of the scene first, drawing poses of the entire character so the timing and acting
can be worked out with a minimum of drawings created. Once the poses are finalized, then
the inbetween drawings are created to complete the action. With computer animation,
keyframes are values at certain frames for the articulation controls of a model, which are
usually set up in a hierarchy. The computer calculates the inbetweens values based on a
spline curve connecting the keyframe values.

When I first began animating with a computer, I was used to
hand-drawn animation and thought a keyframe in one medium was the same as the other. So I
worked on one complete pose, went ahead a few frames, then worked on the next pose. Well,
the inbetweens produced by the computer were completely useless. I ended up having a
keyframe at every frame to get the results I desired.

With computer animation, I learned to work down the hierarchy
of the model, and as I went, created separate keyframes for the different controls at each
level of the hierarchy. I found that controls at some levels needed only a few keyframes
where some at other levels needed keyframes on practically every frame. I also found that
I used far fewer keyframes overall and the inbetween values that the computer would
interpolate for me were far more useful. The important thing with this approach is to have
a clear idea of the action you want to achieve before you start. Plan out the action with
thumbnail sketches and plot timing ideas on an exposure sheet. Have these next to you as
you block out the basic animation. You will find that you will always refer back to these.

<a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#top" target="_blank">Top</a>

<hr style="height: 2px;">

<h2><a name="2dvs3d"></a>2-D VS. 3-D </h2>

One of the biggest differences between hand-drawn animation
and computer animation is the fact that computer animation is truly three dimensional. The
first run cycle I ever animated on the computer looked great from the side view, but when
I looked at it from the front, the arms were going through the body and the knees were
bending the wrong way. From then on I always animated with two views of my character
always showing, so that I could always tell if the animation was working from all sides.

Since computer animation is truly 3-D, you can re-use the
animation of a scene or parts of the animation and not tell that it is the exact same
motion. Many times, if you simply look at a scene of animation from a different camera
angle, it will look completely different. Sometimes, it may seem too similar, so just vary
the timing of the motion or change the motion of an arm or head and it will cease to
resemble the original. This is great for crowd shots, where the re-use of animation is an
easy way to keep the crowd alive.

<a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#top" target="_blank">Top</a>

<hr style="height: 2px;">

<h2><a name="weight&size"></a>WEIGHT & SIZE </h2>

The computer gives the ability to create images that look
absolutely real. Especially with the latest techniques in rendering, texture mapping, ray
tracing and radiosity, you can make an object look just like it?s made of marble or
rubber or whatever you wish. But to make it look like marble or rubber when it is in
motion, has very little to do with the way the object is rendered. It has everything to do
with the way the object is animated. It is animation that gives an object its physical
properties. More that anything else, the timing of the movement of an object defines the
weight of that object.

Two objects, identical in size and shape, can appear to have
two vastly different weights by manipulating timing alone. The heavier an object is, the
greater its mass, and the more force that is required to change its motion. A heavy body
is slower to accelerate than a light one. It takes a large force to get a bowling ball
moving; but once moving, it tends to keep moving at the same speed and requires some force
to stop it.

When dealing with heavy objects, one must allow plenty of time
and force to start, stop or change their movements, in order to make their weight look
convincing. Light objects have much less resistance to change of movement and thus require
much less time to start moving. The flick of a finger is enough to make a balloon
accelerate away. When moving, it has little momentum and even the friction of the air
quickly slows it up.

The way an object behaves on the screen, the effect of weight
that it gives, depend mostly on the spacing of the poses and less on the poses themselves.
Again, no matter how well rendered a bowling ball may be, it does not look like a bowling
ball if it doesn?t behave like one when it is animated.

The proper timing of a motion can also contribute greatly to
the feeling of size and scale of an object or character. A giant has much more weight,
more mass, more inertia than a normal man; therefore he moves more slowly. Like a bowling
ball, he takes more time to get started and once moving, takes more time to stop. Any
changes of movement take place more slowly. Conversely, a tiny character has less inertia
than normal, so his movements tend to be quicker. 

<a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#top" target="_blank">Top</a>

<hr style="height: 2px;">

<a name="thinking character"></a>THE THINKING CHARACTER 

When animating characters, every movement, every action must
exist for a reason. If a character were to move about in a series of unrelated actions, it
would seem obvious that the animator was moving it, not the character itself. All the
movements and actions of a character are the result of its thought process. In creating a
"thinking character," the animator gives life to the character by connecting its
actions with a thought process. Walt Disney said, "In most instances, the driving
forces behind the action is the mood, the personality, the attitude of the
character?or all three. Therefore, the mind is the pilot. We think of things before
the body does them." 

To convey the idea that the thoughts of a character are
driving its actions, a simple trick is in the anticipation; always lead with the eyes or
the head. If the character has eyes, the eyes should move first, locking the focus of its
action a few frames before the head. The head should move next, followed a few frames
later by his body and the main action. The eyes of a character are the windows to its
thoughts; the character?s thoughts are conveyed throught the actions of its eyes.

If the character has no eyes, such as an inanimate object like
a Luxo lamp, it is even more important to lead with the head. The number of frames to lead
the eyes and head depends on how much thought precedes the main action. The animator must
first understand a character?s thought process for any given action. Consider a
character wanting to snatch some cheese from a mouse trap; the eyes will lead the snatch
by quite a bit because this is a big decision. The character needs time to think,
"...Hmm...This looks tricky, is this cheese really worth it or is it just processed
American cheese food?...Oh what the heck...," he decides, and snatches the cheese.

Conversely, if the action is a character ducking to miss a low
flying sheep, the anticipation of the eyes leading the action should be just a couple of
frames. "What the...," and the next thing, he is spitting wool out of his mouth.

The only time that the eyes or head would not lead the action
would be when an external force is driving the character?s movements, as opposed to
his thought process. For example, if that character was hit in the back by the low flying
sheep, the force of the impact would cause the body to move first, snapping the head back
and dragging it behind the main action of the body.

<a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#top" target="_blank">Top</a>

<hr style="height: 2px;">

<a name="moving holds"></a>MOVING HOLDS 

In hand-drawn animation, it is very common to animate an
action, then slow into a pose and hold the drawing of that pose for several frames, then
move into action again. Being two dimensional animation, the action stays alive even with
the use of held drawings. The same goes for puppet and clay animation. But in 3-D computer
animation, as soon as you go into a held pose, the action dies immediately. I?ve seen
it happen with every animator that came out of traditional animation.

It must be the combination of the dimensional, realistic look
and the smooth motion (usually on "ones") that makes a hold cause the motion to
die. The eye picks it up immediately, it begins to look like robotic motion. To combat
this, use a "moving hold." Instead of having every part of the character stop,
have some part continue to move slightly in the same direction, like an arm, a head, or
even have the whole body.

Even the slightest movement will keep your character alive.
Sometimes an action that feels believable in traditional animation, looks too cartoony in
computer animation. Because of the realistic look of computer animation, an animator need
to be aware of how far to push the motion. The motion should match the design of the
character and the world. Animating very cartoony motion with lots of squash and stretch on
a realistic looking object may not look believable, as would realistic motion on a
caricatured object.

This is the pitfall of using motion capture devices to create
final animation. Motion capture from human actors will always look realistic... for a
human. But apply that motion to a chicken and it will look like a human in a chicken suit.
You can use the motion capture data as a starting place, tweak the timing and poses to
make it more caricatured, then apply it to the chicken and the motion will match the
design of the character.

<a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#top" target="_blank">Top</a>

<hr style="height: 2px;">

<a name="emotion"></a>EMOTION 

The personality of a character is conveyed through emotion and
emotion is the best indicator as to how fast an action should be. A character would not do
a particular action the same way in two different emotional states. When a character is
happy, the timing of his movements will be faster. Conversely, when sadness is upon the
character, the movements will be slower. An example of this, in Luxo Jr., is the action of
Jr. hopping. When he is chasing the ball, he is very excited and happy with all his
thoughts on the ball. His head is up looking at the ball, the timing of his hops are fast
as there is very little time spent on the ground between hops because he can?t wait
to get to the ball.

After he pops the ball, however, his hop changes drastically,
reflecting his sadness that the object of all his thoughts and energy just a moment ago is
now dead. As he hops off, his head is down, the timing of each hop is slower, with much
more time on the ground between hops. Before, he had a direction and a purpose to his hop.
Now he is just hopping off to nowhere. 1

To make a character?s personality seem real to an
audience, he must be different than the other characters on the screen. A simple way to
distinguish the personalities of your characters is through contrast of movement. No two
characters would do the same action in the same way. For example, in Luxo Jr., both Dad
and Jr. bat the ball with their heads. Yet Dad, who is larger and older, leans over the
ball and uses only his shade to bat it. Jr., however, is smaller, younger, and full of
energy, he whacks the ball with his whole shade, putting his whole body into it. 1

<a href="http://www.siggraph.org/education/materials/HyperGraph/animation/character_animation/principles/lasseter_s94.htm#top" target="_blank">Top</a>

<hr style="height: 2px;">

<a name="readability of s"></a>READABILITY OF
ACTIONS 

Proper timing is critical to making ideas readable. It is
important to spend enough time (but no more) preparing the audience for: the anticipation
of an action; the action itself; and the reaction to the action (the follow through). If
too much time is spent on any of these, the audience?s attention will wander. If too
little time is spent, the movement may be finished before the audience notices it, thus
wasting the idea.

The faster the movement, the more critical it is to make sure
the audience can follow what is happening. The action must not be so fast that the
audience cannot read it and understand the meaning of it. 4

To make sure an idea or action is unmistakably clear, the
audience?s eye must be led to exactly where it needs to be at the right moment, they
must not miss the idea or action. Timing, as well as staging and anticipation are all
integral to directing the audience?s eye. A well-staged anticipation will be wasted
if it is not timed properly. 1

It is important that only one idea is seen by the audience at
a time. If a lot of action is happening at once, the eye does not know where to look and
the main idea will be overlooked. The object of interest should be significantly
contrasted against the rest of the scene. In a still scene, the eye will be attracted to
movement. In a very busy scene, the eye will be attracted to something that is still. Each
idea or action must be timed and staged in the strongest and simplest way before going on
to the next idea or action. The animator is saying, in effect, "Look at this, now
look at this, and now look at this." 3

In most cases, an action should not be brought to a complete
stop before starting another action; the second action should overlap the first. This
slight overlapping maintains a flow and continuity between whole phrases of actions.

In Luxo Jr., it was very important that the audience was
looking in the right place at the right time, because the story, acting and emotion was
being put across with movement alone, in pantomime, and sometimes the movement was very
subtle. If the audience missed an action, an emotion would be missed, and the story would
suffer. So the action had to be timed and paced so that only Dad or Jr. was doing an
important action at any one time, never both. In the beginning of the film, Dad is
on-screen alone and your eye is on him. But as soon as Jr. hops on-screen, he is moving
faster than Dad; therefore the audience?s eye immediately goes to him and stays
there.

Most of the time Jr. is on-screen, Dad?s actions are
timed to be very subtle, so the attention of the audience is always on Jr. where most of
the story was being told. If Dad?s actions were important, Jr.?s actions were
toned down and Dad?s movements were emphasized then the attention of the audience
would transfer to Dad. For example, when Jr. looks up to Dad after he?s popped the
ball and Dad shakes his head, all eyes are on Jr. 1

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<hr style="height: 2px;">

<a name="story trick"></a>A STORY TRICK 

In storytelling, the timing of ideas and actions is important
to the audience?s understanding of the story at any point in time. It is important
that the animation be timed to stay either slightly ahead of the audience?s
understanding of what?s going on with the story, or slightly behind. It makes the
story much more interesting than staying even with the audience. If the animation is too
far ahead, the audience will be confused; if the animation is too far behind, the
audience, will get bored; in either case, their attention will wander.

Action timed to be slightly ahead of the audience adds an
element of suspense and surprise; it keeps them guessing about what will happen next. An
example of this is at the beginning of Luxo Jr. Dad is on-screen, alone and still; the
audience believes they are looking at a plain inanimate lamp. Unexpectedly, a ball comes
rolling in from off-screen. At this point, both Dad and the audience are confused. The
audience?s interest is in what is to come next.

When the action is timed to be slightly behind the audience, a
story point is revealed to the audience before it is known to the character. The
entertainment comes in seeing the character discover what the audience already knows.
Another application of this is with a dim-witted character who is always behind; the
audience figures it out before he does.

Many of these tricks can be used in concert in any given scene
in order to achieve the strongest impact on an audience. At the end of the dream sequence
in Red?s Dream, Red juggles three balls and catches them with a big finish; the crowd
explodes into wild applause, and Red takes his bows. Slowly the circus ring dissolves to
the interior of the bike shop, the sound of the applause fades into the sound of rain, and
Red, unaware, continues to take his bows. At this point, the audiences has not caught on
to what is happening because the timing of the action is slightly ahead of the audience.
As the room appears, so does the large?50% OFF? tag hanging from Red?s
seat. The animation of the tag is timed to be light in weight; it flops around more
actively than anything else in the scene. This contrast of action directs the
audience?s attention to the tag which is a subtle reminder that Red is still in the
bike shop. The audience is now ahead of the character and watches Red discover where he
really is. Red?s actions were timed to be slow, accentuating his sad emotion. Timing
made the story points clear, the emotion stronger, and the character?s actions were a
result of his thought process; thus, the scene has a strong impact on the audience.

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<hr style="height: 2px;">

<a name="ask why"></a>ASK WHY 

In every step of the production of your animation, the story,
the design, the staging, the animation, the editing, the lighting, the sound, etc., ask
yourself why? Why is this here? Does it further the story? Does it support the whole? To
create successful animation, you must understand why an object moves before you can figure
out how it should move. Character animation isn?t the fact that an object looks like
a character or has a face or hands. Character animation is when an object moves like it is
alive, when it looks like it is thinking and all of its movements are generated by its own
thought process. It is the change of shape that shows that a character is thinking. It is
the thinking that gives the illusion of life. It is the life that gives meaning to the
expression. 3 As Saint-Exup?ry wrote, ?It?s not the eyes, but the
glance - not the lips, but the smile...? 2

Every single movement of your character should be there for a
purpose, to support the story and the personality of your character. It is animation after
all and any kind of motion is possible, and in the world of your story any kind of rules
can exist. But there must be rules for your world to be believable. For example, if a
character in your story can?t fly and then all of a sudden he can fly for no reason,
your world and story will lose credibility with your audience. The movement of your
character and the world of your story should feel perfectly natural to the audience. As
soon as something looks wrong or out of place, your audience will pop out of your story
and think about how weird that looked and you?ve lost them. The goal is to create a
personality of a character and a storyline that will suck your audience in and keep them
entertained for the length of your film. When a film achieves this goal, the audience will
lose track of time and forget about all their worldly cares. For all that any audience
truly wants is to be entertained.

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<hr style="height: 2px;">

<a name="references"></a>REFERENCES

1. Lasseter, John, "Principles of Traditional Animation
Applied to 3D Computer Animation," SIGGRAPH ?87, Computer Graphics, Vol. 21, No.
4, pp. 35-44, July, 1987.

2. Saint-Exup?ry, Wind,
Sand and Stars, Harcourt, Brace and Co., New York,
1932.

3. Thomas, Frank and Johnston, Ollie, Disney Animation? The Illusion of Life, Abbeville Press, New York, 1981.

4. Whitaker, Harold and Halas, John, Timing for Animation, Focal
Press, London, 1981.

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<address>
Last changed March 13, 1999, G. Scott Owen, owen@siggraph.org
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dynafx

21-05-2005, 03:59 PM

We dont hear much of lasseter's interview, though this is old, still, worth reading it 
 


Regus London Film Festival
interviews 2001 <o:p></o:p>

 <o:p></o:p>

John Lasseter (I) <o:p></o:p>

 <o:p></o:p>

John Lasseter is the
founder and creative frontman of Pixar, the computer animation pioneers behind
Toy Story, A Bug's Life and the forthcoming Monsters Inc. On-stage at the NFT,
he tells Jonathan Ross about his hopes for CGI, how he upset the Harry Potter
people and why traditional animation will never die <o:p></o:p>

 <o:p></o:p>

Monday November 19, 2001 <o:p></o:p>

 <o:p></o:p>

Jonathan Ross: Good evening, ladies and gentlemen. Mr John Lasseter, ladies and
gentlemen. <o:p></o:p>

[Applause] <o:p></o:p>

John Lasseter:<s