Traditional Animation Methods

Before the advent of the computer animation, all frames in an animation had to be drawn by hand. Considering that each second of animation contains 24 frames (film), one can only imagine the tremendous amount of work that has to go into creating even the shortest of animated films. A couple of different techniques were developed for creating animation by hand.

Traditional animation include:

2D:

3D:

Cel Animation

The word 'cel' comes from 'celluloid', the material which was used in early motion pictures, and refers to the transparent pieces of film used in hand-drawn animation (even though this film is now usually made from acetate.) When creating an animation using this method, each character is drawn on a separate piece of transparent film. A background is also drawn on a separate sheet of opaque paper. Then, when it comes to shooting the animation, the different characters are overlaid on top of the background in each frame. (A frame is like a snapshot of the action at one instant in time and is composed of all the cels including the background being used at that instant.) This method also saves time in that the artists do not have to draw in entire frames, but rather just the parts that need to change such as individual characters. Sometimes, even separate parts of a character's body are placed on separate cels.

Key Frames

Considering the immense amount of work that has to go into the making of an animation sequence, the drawing or painting is usually done by more than one person. After a storyboard has been laid out, the senior artists go and draw the major frames of the animation. These major frames are frames in which a lot of change takes place. They are the key points of the animation. Later, a bunch of junior artists draw in the frames in between. This way, the workload is distributed and controlled by the key frames. By doing work this way, the time in which an animation can be produced is cut dramatically, depending on the number of people working on the project. Work can be done simultaneously by many people, thus cutting down on the time needed to get a final product out. Key frames, in conjunction with 'tweening', are still used in many forms of computer animation.

Rotascoping

Rotascoping involves using images from moving video or film as the basis for an animation. For example, let us say that you want to animate a frog jumping. It is a lot easier to draw the motion and shape of the frog in the different parts of the animation when you have some reference, such as video, as opposed to imagining it in your head. With the help of rotascoping, one can animate some complex scenes that would be very hard to visualise. One disadvantage of rotascoping is that you have to get the exact video you want to animate. For example, if you want a dog running across the screen, video of a dog running away from you will not do.

Flip-book Animation

This is also known as 'frame-based' animation and is the simplest kind of animation to visualise. Historically, just as the name suggests, it consisted of a series of progressive drawings, one on each page of a book, through which the viewer flipped thus creating the illusion of movement. Within the computer environment, flip-book animation means displaying a sequence of independent graphics files. The most frequent form is slide-show presentations, but many GIF89a animations are also essentially flip-book animations too.

Many methods of traditional animation have been carried through (often as metaphors or methodologies - e.g keyframes, onion-skinning, etc - into the software used to produce computer-generated 2D animation.

Computer animation

Computer animation is a term that covers a wider area than cel or keyframe animation.. The computer can fill various roles in animation:

Computer-Assisted animation

Computer-assisted animation, or keyframe animation refers to creating two-dimensional graphic objects and animating them.

A frame-based animation imitates the original animation techniques of drawing each frame carefully by hand. The computer technology significantly improves the speed and ease with which each frame is created. The final animation is assembled from a sequence of frames (bitmaps) and is in a form of a movie file (usually with .avi or .mov suffix). The software used to create the animation does is automatically upon your choice of "Create a movie" or similar command.

A cel-based animation evolved from frame-based animation techniques as a way to speed up the production. The name derives from a technique of using celluloid layers to overlay the active elements in an animation frame on a static background. Often the process of creating such an animation is greatly automated by computer - you just specify the two positions of an object and the computer will create frames approximating the movements of the object between these positions (this is the case when you are working with Macromedia Director).

An object animation (also known as Sprite, Path and Vector Animation) is the simplest of the three. Instead of creating animation files that you import to your presentation, program or title, you animate objects within the title-building software (such as AfterEffects). Object animation usually involves moving an unchanging object along a path. You might be able to rotate, resize or add filters to it as it moves.

Scripting Systems

Scripting Systems were the earliest type of motion control systems. The animator writes a script in the animation language. Thus, the user must learn this language and the system is not interactive. One scripting system is ASAS (Actor Script Animation Language), which has a syntax similar to LISP. ASAS introduced the concept of an actor, i.e., a complex object which has its own animation rules. For example, in animating a bicycle, the wheels will rotate in their own coordinate system and the animator doesn't have to worry about this detail. Actors can communicate with other actors be sending messages and so can synchronize their movements. This is similar to the behavior of objects in object-oriented languages.

Procedural Animation

Procedures are used that define movement over time. These might be procedures that use the laws of physics (Physically - based modeling) or animator generated methods. An example is a motion that is the result of some other action (this is called a "secondary action"), for example throwing a ball which hits another object and causes the second object to move.

Representational Animation

This technique allows an object to change its shape during the animation. There are three subcategories to this. The first is the animation of articulated objects, i.e., complex objects composed of connected rigid segments. The second is soft object animation used for deforming and animating the deformation of objects, e.g. skin over a body or facial muscles. The third is morphing which is the changing of one shape into another quite different shape. This can be done in two or three dimensions.

Stochastic Animation

This uses stochastic processes to control groups of objects, such as in particle systems. Examples are fireworks, fire, water falls, etc.

Behavioural Animation

Objects or "actors" are given rules about how they react to their environment. Examples are schools of fish or flocks of birds where each individual behaves according to a set of rules defined by the animator.

Typical file suffixes for an animation:

.avi
.mov
.flc
.fli
.mmm
.gif

 

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