A Multimedia Bargain?
Animation is the illusion of motion. Animation makes exploded diagrams explode, procedures proceed, and working models work — all in front of the user’s eyes. And, in the world of multimedia, animation is a bargain. On the “bang-for-the-Buck-Mark-or-Yen” scale, animation is right up there with video for effectiveness but at half the cost or less. It’s definitely worth looking into.
Use Animation for What it Does Well
No medium is a bargain unless it is used effectively. Use animation for what it does well. Use it to convey change, movement, and progress. Use animation to
* Show things that move and change. Use animation to
explain a complex me chanical device with many
moving parts, such as a laser printer.
* Analyze processes. Use animation to reveal repeated
patterns of action, bottlenecks, and the relative speed
of processes, by giving viewers a new frame of
* Explain abstract concepts. Animation may be the
only way to show ideas and abstractions present only
in the mind.
* Improve comprehension. One study showed that for
improving the comprehension of business
presentations, animation (without transitions)
outperformed text, static graphics, transitions, and
their combination (3M Meeting Management Institute
* Increase interest. Animation increased interest and
was strongly preferred by computer-science students
studying algorithms (Stasko, Badre, and Lewis 1993).
In business presentations, animations combined with
transitions increased audience attention and the
presenter’s persuasiveness (3M Meeting Management
* Focus the viewer’s attention. Use animation to
emphasize important aspects of a graphic or display.
* Handle sensitive subjects. Animated characters are
better than videotaped real characters for sensitive
subjects like sex education, ethnic relations, and other
subjects where the animated characters let the viewers
concentrate on the idea and not on the identity or
appearance of the actors.
* Show dangerous subjects. Animation lets you create
a world of hazards without danger to the user or to
the cameraman. Wiley Coyote fell from cliffs, was run
over by cars and trucks, and was blown up many
times in pursuit of the Roadrunner. Yet he sprang
back to life to continue the chase. Beep. Beep.
Use the Right Type of Animation
There are several different ways to create animation, each with its own costs and benefits. The first step in bargain-hunting is picking the right type.
Cel animation. In classic cel animation you produce a separate drawing for each frame of the animation. (Cel is short for cellophane, the material early animations were drawn on.) Each drawing differs slightly from the Previous one (Shapiro and Rubin 1988), as in this sequence for turning pages.
The file consists of a simple series of static images. Several industry-standard formats are defined for such a sequence of images: PICS, Video for Windows (Audio-Video Interleaved), or QuickTime. But because each frame requires the storage of a whole image, cel animation can consume storage space as well as processing power. However, if there is relatively little difference between subsequent frames, compression algorithms can often reduce the storage size.
Sprite animation. Sprites are two-dimensional images that move in front of a fixed background. These sprites can change their appearance to simulate movement within the sprite. Sprite animation is probably the most common form of computer animation because it is simple and economical. With sprite animation, the book with the turning pages would look the same, but the page that turned would be a sprite in front of a background drawing of the other pages of the book. Here is the background:
Storage and processing requirements are moderate because the unchanged part (background) is stored only once. File formats, however, are proprietary: Macromedia Director and Animator Pro, for example.
Color cycling animation. Color cycling creates an illusion of motion by repeatedly redefining the colors in a static graphic. Color cycling is easier to do than to understand. It relies on the fact that computer colors are just numeric codes. A palette or color look-up table specifies what color each numeric code actually represents. With color cycling you draw one picture that shows the moving object in successive positions. In each position you draw the moving object in the color of a different numeric code. In the palette, however, all of the codes used by the moving object are defined as the same color as the background, except the one that shows the object in its starting position. For example, in this endview of a book, all of the page positions are defined as different numbers. All but one of these numbers is defined as the background color.
To simulate motion, the codes for successive positions of the moving object are redefined as the visible color while all others are the background color. Here’s how the animation appears to the user at various stages.
Color cycling is especially effective for animating repetitive movement in an enclosed area as long as successive positions of the moving object do not overlap. It works well for showing flames or flowing liquid. Because it does not require storing and displaying many separate drawings, color cycling is economical. There are, alas, no industry-standard formats for color-cycling animation.
3D model animation. Three-dimensional models are sometimes used to create animations. First, the designer builds a detailed model of the objects to be shown in the animation. The computer then calculates what the scene would look like from a particular viewpoint and with particular lighting conditions. This is called rendering the scene. The model or the viewpoint is shifted slightly and the process repeated to generate the next frame of animation.
Rendering richly detailed 3D scenes requires vast computer resources. Creating the models for a one-minute 3D animation can take three to five days (Apple Computer 1993). Rendering one second of ray-traced animation at 600×480 pixels can take one hour on a 86040 Macintosh. As a result, 3D modeling is seldom used for real-time animation. It is almost always used to generate the individual frames for cel animation. Furthermore, if the subsequent images are highly detailed or differ greatly, compression algorithms will have little effect.
Stop-motion. In stop-motion animation, you photograph real objects, shifting or modifying them slightly between photographs. Stop-motion animation can show the assembly or disassembly of a complex piece of machinery. It has a magic, comical feel as inanimate objects spring to life.
Stop-motion is really digital video, albeit minus intervening frames, and is a storage and processing hog. The file formats, however, follow industry standards, such as Quicktime and Video for Windows.
To recap the trade-offs among the various animation techniques:
Keep Animation Cost Low
Regardless of what type of animation you use, you can take steps to keep costs in check. As always, good design leads the way.
Simplify. Simplify. Simplify. To reap the bargain of animation, you’ve got to keep it simple and design for low-cost production and play back. Fortunately, you can do so without compromising communication effectiveness.
Don’t overload the viewer with meaningless animation by showing too much too fast (3M Meeting Management Institute 1992). The display becomes distracting when we try to show too much spatially by crowding the display, or too much temporally by changing too rapidly or abruptly (Baecker and Small 1990). Remember that users can pay attention to only one moving object at a time. If the animation includes simultaneous movements by separate objects, let the user cycle or repeat the scene.
Do not put a busy background behind animated characters. Leave large areas with a plain background on which animated characters can move. Avoid intricate details, bright colors, high-contrast figures, or anything else that will draw attention away from the animated character.
Also, users cannot attend to intricate details in moving objects. In animation, pay more attention to the overall contours of shapes. If these are right, few interior lines win be needed. Make all critical events clear from outline contours alone. Do not disguise pertinent information in a tangle of lines. Remember that single pixel lines may not display correctly after the image has been compressed and decompressed (Apple Computer 1993).
For animation, you seldom need more than a dozen colors. Use flat color as in cartoons and on the comic pages.
Create Reusable Components. Make your animations modular and reusable. Design elemental animations that you can combine to compose more complex scenes. One way is to draw your animation components in paralline perspective rather than true perspective. In this way, when the components are combined, they can be placed anywhere in the display without having to worry about vanishing points.
Make your animation sequences reusable. For example, create an animation showing a screwdriver removing a screw and you can use that module in every procedure that requires removing a screw.
By choosing the right type of animation and designing it carefully, you can communicate some tough messages effectively and economically.