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1. A Servey of COMPUTER GRAPHICS

Computers have become a powerful tool for the rapid and economical production of pictures. There is virtually no area in which graphical displays cannot be used to some advantage, and so it is not surprising to find the use of computer graphics so widespread. Although early pplications in engineering and science had to rely on expensive and cumbersome equipment, advances in computer technology have made interactive computer graphics a practical tool. Today, we find computer graphics used routinely in such diverse areas as business, industry, government, art, entertainment, advertising, education, research, training, and medicine.
Figure 1-1 shows a few of the many ways that graphics is put to use. Our introduction to the field of computer graphics begins with a tour through a gallery of graphics applications.
1.1 Computer-Aided Design
For a number of years, the biggest use of computer graphics has been as an aid to design. Generally referred to as CAD, computer-aided design methods provide powerful tools. Parts design and drafting are done interactively, producing outlines (Fig. 1-2) or more realistic renderings (Fig. 1-3). When an object s dimensions have been specified to the computer system, designers can view any side of the object to see how it will look after construction. Experimental changes can be made
freely since, unlike hand drafting, the CAD system quickly incorporates modifications into the display of the object. The manufacturing process also benefits in that layouts show precisely how the object is to be constructed. Figure 1-4 shows the path to be taken by machine tools over the surfaces of an object during its construction.
Numerically controlled machine tools are then set up to manufacture the part according to these construction layouts.
Electrical and electronics engineers rely heavily on CAD methods. Electronic circuits, for instance, are typically designed with interactive computer graphics systems. Using pictorial symbols to represent various components, a designer can build up a circuit on a video monitor (Fig. 1-5) by successively adding components to the circuit layout. The graphics display can be used to try out alternate circuit schematics as the designer tries to minimize the number of components or the space required for the circuit. Figure 1-6 displays a completed circuit board generated on a video monitor. Similar techniques are used to design communications networks and water and electricity supply systems.
Automobile, aircraft, aerospace, and ship designers use CAD techniques in
the design of various types of vehicles. Wire-frame drawings, such as those shown in Fig. 1-7, are used to model individual components and plan surface contours for automobiles, airplanes, spacecraft, and ships. Individual surface sections and vehicle components (Fig. 1-8) can be designed separately and fitted together to display the total object. Simulations of the operation of a vehicle are often run to test the vehicle performance, as in the example of Fig. 1-9. Realistic renderings, such as
those shown in Fig. 1-10, allow the designer to see how the finished product will appear.
Building designs are also created with computer graphics systems. Architects interactively design floor plans (Fig. 1-11), arrangements of doors and windows, and the overall appearance of a building. Working from the display of a building layout, the electrical designer can try out arrangements for wiring, electrical outlets, and fire warning systems. Utilization of space in the office or on the manufacturing floor is worked out using specially designed graphics packages.
Three-dimensional building models (Fig. 1-12) permit architects to study the appearance of a single building or a group of buildings, such as a campus or industrial complex. Using sophisticated graphics packages, designers can go for a simulated "walk" through the rooms or around the outsides of buildings to better appreciate the overall effect of a particular design.




1-2 Graphs, Charts, and Models

A number of commercially available graphics programs are designed specifically for the generation of graphs and charts. Often a graph-plotting program will have the capability of generating a variety of graph types, such as bar charts, line graphs, surface graphs, or pie charts. Many programs are capable of summarizing data in either two-dimensional or three-dimensional form. Three-dimensional plots are typically used to illustrate multiple relationships, as in the graphs of Figs. 1-13 and 1-14. In some cases (Fig. 1-15), three-dimensional graphs are used to provide a more dramatic or more attractive presentation of data.
Business graphics, one of the most rapidly growing areas of application, makes extensive use of visual displays as a means for rapidly communicating the vast amounts of information that are compiled for managers and other individuals in an organization. Graphs and charts are typically used to summarize financial, statistical, mathematical, scientific, or economic data, and several graphs are often combined in one presentation (Fig. 1—16). These graphs are generated for research reports, managerial reports, consumer information bulletins, and visual aids used
during presentations. Figure 1-17 illustrates a time chart used in task planning.
Project management techniques make use of time charts and task network layouts to schedule and monitor projects. Some graphics systems include the capability of generating 35mm slides or overhead transparencies from the graphs displayed on a video monitor.

1-3 Computer Art

Both creative and commercial art applications make extensive use of computer graphics. The abstract display in Fig. 1-23 is created by plotting a series of mathematical functions in varying colors. Figure 1-24 illustrates another type of art design drawn with a pen plotter.
"Paintbrush" programs allow artists to create pictures on the screen of a video monitor, somewhat like the character in Fig. 1-25. Actually, the artist might draw the picture on a "graphics tablet" using a stylus as input. A paintbrush program was also used to create the characters in Fig. 1-26, who seem now to be busy on a creation of their own. Paintbrush programs are not limited to cartoon characters;

they are also used to produce the sort of art seen in Figs. 1-27 and 1-28.
Computer-generated art is widely used in commercial applications. Figure
1-29 illustrates a rug pattern that was designed with a computer graphics system.
Logos and advertising designs for TV messages are now commonly produced with graphics systems. Figure 1-30 shows two examples of computer-generated art for use in TV advertising spots. In addition, graphics programs have been developed for applications in publishing and word processing, which allow graphics and textediting operations to be combined. Figure 1-31 is an example of the type of output that can be generated with such systems.