Download Animations - Introduction to Computer Graphics - Lecture Notes and more Study notes Computer Graphics in PDF only on Docsity!
Introduction to Computer Graphics
Lecture 45
Animations
The passage of time has fascinated artists, scientists and theologians for thousands of years. Naturally they have attributed to it different interpretations, different implications and different conclusions. Nevertheless there seems to be general agreement on one aspect of time; that we are all conditioned by it and that, whether we like it or not, there is a time space into which we inevitably have to fit.
Einstein, among other well known names in the world of science, made a special study of time in relation to his research in physics. His theory of relativity maintains that space and time are merely different aspects of the same thing. Since then other physicists have pointed out that objects can be moved backward and forward in space, but nothing can be moved back in time.
Another method of describing the concept of time is through the ‘three arrows of time’. The first ‘arrow’ is thermodynamic and can be seen operating when sugar dissolves in hot water. Second, is the historical ‘arrow’, whereby a single-celled organism evolves to produce more complex and varied species? The third is the cosmological ‘arrow’ which is the theory that the universe is expanding from a ‘big bang’ in the past. This cosmic expansion cannot be reversed in time. While the principle of relationships between the ‘time arrows’ is still to be worked out on a scientific level, the actual application of it is constantly related to all work which utilizes it, such as music and the performing arts. In the latter it is one of the most important raw materials.
In terms of animation, the idea of film time is one of the most vital concepts to understand and to use. It is an essential raw material which can be compressed or expanded and used for effects and moods in a highly creative way. It is, therefore, essential to learn and to understand how time can be applied to animation. The great advantage of animation is that the animator can creatively manipulate time since an action must be timed prior to carrying out the actual physical work on a film.
It is also essential to understand how the audience will react to the manipulation of time from their point of view. Time sense or ‘a sense of timing’, therefore, is just as important as color sense and skill of drawing or craftsmanship in film animation.
It has to be realized that while a performance on stage and on the screen requires a basic understanding of how timing works, this lecture is primarily confined to hand drawn animation which up to this point in film history still comprises 90% of all output in the animation medium.
Timing for TV series
For economic reasons, TV series are made as simply as possible from the animation point of view. This approach is generally known as limited animation. Animation is expensive, non-animation is cheaper. So to keep the films lively the plots are usually carried along by means of dialogue. It is often necessary to work with prerecorded blocks of dialogue which must remain intact. If this dialogue is well recorded for maximum dramatic effect, lengths of pauses between phrases cannot be changed (except within very narrow limits) without destroying that effect. In this case, the overall timing of long sections of the film is governed entirely by the dialogue. (There could be, however, considerable flexibility for more detailed timing within this fixed overall length.)
The director has room to maneuver sections. So, if the total timing for all the recorded dialogue is subtracted from the required length for the whole film, this gives the amount of time that is available without dialogue. This can then be split up in the normal way and distributed throughout the film to give the best effect.
Limited animation
With limited animation as many repeats as possible are used within the 24 frames per second. A hold is also lengthened to reduce the number of drawings. As a rule not more than 6 drawings are produced for one second of animation. Limited animation requires almost as much skill on the part of the animator as full animation, since he must create an illusion of action with the greatest sense of economy.
Full animation
Full animation implies a large number of drawings per second of action. Some action may require that every single frame of the 24 frames within the second is animated in order to achieve an illusion of fluidity on the screen. Neither time nor money is spared on animation. As a rule only, TV commercials and feature-length animated films can afford this luxury.
Animation is expensive and time-consuming. It is not economically possible to animate more than is needed and edit the scenes later, as it is in live-action films. In cartoons the director carefully pre-times every action so that the animator works within exact limits and does no more drawings than necessary.
Ideally, the director should be able to view line test loops of the film as it progresses and so have a chance to make adjustments. But often there is no time to make corrections in limited animation and the aim is to make the animation work the first time.
Timing for Animation in general
Timing in animation is an elusive subject. It only exists whilst the film is being projected, in the same way that a melody only exists when it is being played. A melody is more easily appreciated by listening to it than by trying to explain it in words. So with cartoon timing, it is difficult to avoid using a lot of words to explain what may seem fairly simple when seen on the screen.
on by a certain arrangement of muscles which tend to work against gravity. Thirdly, there is the psychological reason or motivation for his action—whether he is dodging a blow, welcoming a guest or threatening someone with a revolver.
A live actor faced with these problems moves his muscles and limbs and deals with gravity automatically from habit, and so can concentrate on acting. An animator has to worry about making his flat, weightless drawings move like solid, heavy objects, as well as making them act in a convincing way. In both these aspects of animation, timing is of primary importance.
Part of the working storyboard of The Story of the Bible by Halas and Batchelor. At this stage the director works out the smooth visual flow of the film, the editing, camera movements and so on. All these elements combine to tell the story in an interesting way.
The storyboard
A smooth visual flow is the major objective in any film, especially if it is an animated one. Good continuity depends on coordinating the action of the character, choreography, scene changes and camera movement. All these different aspects cannot be considered in isolation. They must work together to put across a story point. Furthermore the right emphasis on such planning, including the behaviour of the character, must also be realised.
The storyboard should serve as a blueprint for any film project and as the first visual impression of the film. It is at this stage that the major decisions are taken as far as the film's content is concerned. It is generally accepted that no production should proceed until a satisfactory storyboard is achieved and most of the creative and technical problems which may arise during the film's production have been considered.
There is no strict rule as to how many sketches are required for a film. It depends on the type, character and content of the project. A rough guideline is approximately 100 storyboard sketches for each minute of film. If, however, a film is technically complex, the number of sketches could double. For a TV commercial, more sketches are produced as a rule because there are usually more scene changes and more action than in longer films.
The basic unit of time
in animation
The basis of timing in animation is the fixed projection speed of 24 frames per second (fps) for film and video. While other projection speeds have been used in the past the standard projection rate for film of all formats—16mm, 35mm and
70mm remains 24 fps. On television and video this becomes 25 frames per second (PAL) or 30 fps (NTSC), but the difference is usually imperceptible.
The thing to remember is that if an action on the screen takes one second it covers 24 frames of film, and if it takes half a second it covers 12 frames and so on.
24 frames of film go through the projector every second (25 on television). This fixed number of frames provides the basis on which all actions are planned and timed by the director.
For single frame animation, where one drawing is done for each frame, a second of action needs 24 drawings. If the same action is animated on double frames, where each drawing is photographed twice in succession, 12 drawings are necessary out the number of frames and hence the speed of the action would be the same in both cases.
Whatever the mood or pace of the action that appears on the screen, whether it be a frantic chase or a romantic love scene, all timing calculations must be based on the fact that the projector continues to hammer away at its constant projection rate. That is— fps for film and either 25 fps or 30 fps for television and video depending on format. The unit of time within which an animator works is, therefore, 1/24 sec, 1/25 sec or 1/30 sec and an important part of the skill, which the animator has to learn is what this specific timing ‘feels’ like on screen. With practice the animator also learns what multiples of this unit look like—3 frames, 8 frames, 12 frames and so on.
Animation and properties of matter
The basic question which an animator is continually asking himself is: ‘What will happen to this object when a force acts upon it?’ And the success of his animation largely depends on how well he answers this question.
All objects in nature have their own weight, construction and degree of flexibility, and therefore each behaves in its own individual way when a force acts upon it. This behavior, a combination of position and timing, is the basis of animation. Animation consists of drawings, which have neither weight nor do they have any forces acting on them. In certain types of limited or abstract animation, the drawings can be treated as moving patterns. However, in order to give meaning to movement, the animator must consider Newton's laws of motion which contain all the information necessary to move characters and objects around. There are many aspects of his theories which are important in this book. However, it is not necessary to know the laws of motion in their verbal form, but in the way which is familiar to everyone, that is by watching things move. For instance, everyone knows that things do not start moving suddenly from rest—even a cannonball has to accelerate to its maximum speed when fired. Nor do things suddenly stop dead—a car hitting a wall of concrete carries on moving after the first impact, during which time it folds itself rapidly up into a wreck.
It is not the exaggeration of the weight of the object which is at the centre of animation, but the exaggeration of the tendency of the weight—any weight—to move in a certain way.
Cartoon film can also be a dramatic medium. This particular quality can be achieved, among other means, by speeded up action and highly exaggerated timing. The difference between an action containing caricature, or humour or drama, may be very subtle. Eventually, with enough experience in animation timing, it becomes possible to emphasise the difference.
Caricatured matter has the same properties as natural matter, only more so. To understand how cartoon matter behaves it is necessary to look more closely into the way matter behaves naturally.
Cartoon is a medium of caricature—naturalistic action looks weak in animation. Look at what actually happens, simplify down to the essentials of the movement and exaggerate these to the extreme.
Cause and effect
There is a train of cause and effect which runs through an object when it is acted upon by a force. This is the result of the transmission of the force through a more or less flexible medium (ie caricatured matter). This is one aspect of good movement in animation.
An animator must understand the mechanics of the natural movement of an object and then keep this knowledge in the back of his mind whilst he concentrates on the real business of animation. This is the creation of mood and conveying the right feeling by the way an action is done.
Examples of cause and effect:
Figs A and B
A rope wrapped around anything and pulled tight has the tendency shown. How far the reaction goes depends on:
i. the strength of the forces pulling the rope. ii. the flexibility or rigidity of the object being squeezed. Exaggerate the tendency.
A A rope wrapped round something. B The ends of the rope are pulled tight.
Fig. C
On the seesaw, the end of the plank with the smaller stone tends to stay where it is to begin with because of its inertia, so bending plank D. A moment later it starts to accelerate and the plank springs back with the opposite curvature causing the stone to w h i z z o u t o f t h e s c r e e
part, must see that plenty of force is applied to the cannonball to make it start, stop or change direction.
Light objects have much less resistance to change of movement and so behave very differently when forces act on them. A toy balloon (Fig. B) needs much less time to start it moving. The flick of a finger is enough to make it accelerate quickly away. When moving, it has little momentum and the friction of the air quickly slows it up, so it does not travel very far.
B A balloon needs only a small force to move it, but air resistance quickly brings it to rest. In both these examples a circle is being animated. The timing of its movements can make it look heavy or light on the screen.
The way an object behaves on the screen, and the effect of weight that it gives, depends entirely on the spacing of the animation drawings and not on the drawing itself. It does not matter how beautifully drawn the cannonball is in the static sense, it does not look like a cannonball if it does not behave like one and the same applies to the balloon, and indeed to any other object or character.
Fast run cycles
An eight frame run cycle—that is four frames to each step—gives a fast and vigorous dash. At this speed the successive leg positions are quite widely separated and may need drybrush or speed lines to make the movement flow. Drawing 5 shows the same position as drawing 1 but with opposite arms and feet. Similarly drawings 6 and 2, 7 and 3, and 8 and 4 show the same positions. These alternate positions should be varied slightly in each case, to avoid the rather mechanical effect of the same positions occurring every four frames.
A twelve frame cycle gives a less frantic run, but if the cycle is more than sixteen frames the movement tends to lose its dash and appear too leisurely.
The body normally leans forward in the direction of movement, although for comic effect a backward lean can sometimes work. If a faster run than an eight frame repeat is needed, then perhaps several foot positions can be given on each drawing, to fill up the gaps in the movement, or possibly the legs can become a complete blur treated entirely in dry-brush.
In the first example, drawing 4 is equivalent to the ‘step’ position in a walk, with the maximum forward and backward leg and arm movement. In a run it is also the point at which the centre of gravity of the body is farthest from the ground, that is, in mid-stride. In drawing 1 the weight is returning to its lowest point, which is in drawing 2. In drawing 3 the body starts to rise again as the thrust of the back foot gives the forward impetus for the next stride.
These are both examples of eight frame run cycles. This means four drawings to each step. Drawings 1 and 5 show the same leg and arm positions but with opposite feet, and so do 2 and 6, 3 and 7, 4 and
- In such a short cycle these positions should be varied slightly to avoid a mechanical effect.
Timing and music
Ever since the very first animated productions, Disney's Steamboat Mickey and Fischinger's abstract film Brahm's Hungarian Dances , it was clear that there is a strong relationship between animation and music. This relationship can be explained on two accounts. First, both elements have a basic mathematical foundation and move forward at a determined speed. Second, since animation is created manually frame by frame, it can be fitted to music in a very exact manner. It is further able to capture its rhythm, its mood and hit the beat right to the frame. Most animation makes good use of this advantage.
In general principle it is more difficult to follow the rhythm of a musical composition with its mood than its beat. The latter aspect of the music is easily measured, since beats are fitted into bar units of defined time length and are interpreted in time units.
Bars can contain various numbers of beats and these must be measured to the film frame. Having done this, it is comparatively easy to fit the animation to the speed of the beat and find the right type of movement to follow the music, whether it is a slow waltz of 36 frames, or 4 frames for rock music. A beat can be emphasised by synchronisation of the feet but it works better if the whole body is used. In quick beats of 3,4 or 6 frames
made from field X to field Y so the screen centre moves towards the south-east. This means that under the camera, the table must move north-west. Fig. C is an enlargement of this table move, showing how the cameraman divides the line to achieve a smooth movement from X to Y. At the same time he measures the distance the camera travels on its column during the track, and divides this in exactly the same way as Fig. C, so that camera and table top move smoothly together. Fig. D is a similar track and table move which includes a tilt. This would also be done as a table move.
Tracks and table moves are usually animated on single frames.
A The director's timing of tracks is finalised by the animator in the ‘camera instructions’ column on the exposure sheet.
B The accompanying field key.
C Enlargement of field centres from Fig. B, inverted for use as table move.
D Another example of a track including a table tilt.
