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Natural and Not-So-Natural Computer Graphics

Published onApr 23, 2021
Natural and Not-So-Natural Computer Graphics

Man’s prolific need for graphic expression can be seen in telephone booths, subway stations, and public men’s rooms. More constructively, graphic media have been indigenous to architects. Traditional applications range from the thumbnail sketch to the rendering to the working drawing. In general, the conveniences of two-dimensional graphic representation have warranted overcoming the technical difficulties of describing three-dimensional events; consequently, mechanical drawing has become the “Latin” of all architecture students.

Now machines can do mechanical drawing too. So-called computer graphics has popularized the architect-machine dialogue by affording a natural language—the picture—where the designer can talk to the machine graphically and the machine can graphically respond in turn. This congenial technique is surely a natural way for architects to express their thoughts and is certainly in vogue. In the past few years, however, it has so dramatically overstated itself that the “message” has indeed become dominated by the “medium.”

Computer graphics is not a synonym for computer-aided design. The significance of graphic interaction can be no greater than the meaningfulness of the content in the transaction. No matter how fancy and sophisticated the computer graphics system, it is only a glorified blackboard or piece of paper (even though possibly three dimensional), that is, until it overtly “talks back” and actually participates in the dialogue. Nonetheless, let us isolate computer graphics for a moment and look at it as a medium of communication.

There exist two families of graphic mechanisms: those devices used to “input” information to the machine and those for the machine to “output” information to the designer. One particular output mechanism of prime importance is the cathode-ray tube, a televisionlike display device. An electron beam, positioned by the computer, sweeps across the face of the scope (in an “on” or “off” state) to draw a picture by exciting tiny phosphors that glow for about a twentieth of a second. Once traced, the image is regenerated and continually redrawn on the face of the screen until a change in content imposes a recalculation of the beam’s path. This regeneration is costly because, in order to deliver the illusion of a still image, it must occur between twenty and forty times per second, depending on the complexity of the picture.

The cathode-ray tube’s most common input device is the light pen. Rather than squirt out light, this stylus is a sensing device that can discern the light of the electron beam. With this instrument the designer can either detect lines, points, or characters, or he can drag about a spot of light, a tracking cross, to draw lines. At present it is not much like a pencil; it is a blunt pointer and to write with it is like applying a crayon to a postcard. The picture is small, the lines are thick, and the complexity of the displayed image is limited. Nonetheless, at present it is one of the more acceptable vehicles for research and does allow the necessary, realtime graphic intercourse.

The awkwardness of display devices such as the cathode-ray tube goes beyond clumsiness. For example, one original acclaim in computer graphics was that “crooked lines are automatically turned into straight ones” (and if properly programmed, can even make them perfectly horizontal or vertical to the nearest millionth of an inch). Unfortunately, “instant accuracy” is not always desirable. In a design dialogue the wobbliness of lines often expresses the degree of clarity of architectural thought. The embodiment of an idea should reveal and be congruous with the stage of the design. One does not sketch with a 6H pencil and a straightedge or make working drawings freehand with a felt pen. The refinement of a project is a step-by-step process of sharpening both the comprehension and representation of one’s image of the problem. A straight-line “sketch” on a cathode-ray tube could trigger an aura of completeness injurious to the dialogue as well as antagonistic to the design.

Computervision’s INTERACT-GRAPHIC. Presently under development, this terminal combines several low-cost facilities into one configuration that will allow a high level of interaction. The unit is designed as a transition between present methods and future computer graphics. With this device the operator can even use his own pencil.

Computer Displays’ Advanced Remote Display Station (ARDS). This threefaced configuration was designed for the Department of Architecture at M.I.T. Each screen is a storage tube, a device that will retain an image on the face of the scope without retracing with the electron beam. The scope does not allow dynamic displays (rotation, translation, etc.) and does not allow erasing parts of a picture without recreating the whole image. However, the unit requires very little computing in communication and costs less than 10 percent of an IBM 2250.

The Stanford Research Institute terminal used in the Augmented Human Intellect Research Center. The scope is a commercial (875 line) television monitor.

A mouse, used on both the Stanford Research Institute terminal and the ARDS. This mechanism is an input device, a cheap device ($400), and a clumsy device.

The IBM 2250. (Photograph courtesy of the IBM Corporation)


The Adage display unit.

The clumsiness of computer graphics hardware is surrounded with technical difficulties, and, even when tackled, its resolution will not yield the same textural feeling as graphite on paper. Computer displays will force a new doodle vernacular if they are to capture those original ideas that usually reside on the backs of envelopes. Displays will have to allow for hazy negotiations to be sloppily expressed. In the meantime the important work of Timothy Johnson (1963) satifies the research need for a “sketchpad.”

Beyond the antisketch nature of our present computer sketch pads, there is a second awkwardness. Traditionally, the architect has drawn plans, sections, elevations—two-dimensional representations—to describe graphically to himself and others his three-dimensional vision of an architectural solution. From the two-dimensional documents, a three-dimensional representation, a physical model or perspective drawing, can be extrapolated. More recently the design process has been inverted in that we sketch with study models of clay, cardboard, styrofoam, or little wooden blocks. (Unfortunately, the gestalt of the forms generated by these three-dimensional study models unconsciously implies the form of the final solution.) In the later stages of design, sections are derived from the model in order to study or represent aspects concealed by, or unrepresentable in, the physical model.

The Rolls Royce of displays, the IBM Cambridge Scientific Center’s 2250, model 4, with Sylvania tablet. This configuration has a small computer (an IBM 1130) devoted to maintaining the graphics. The Sylvania tablet has been added to give both a smoother and a more simple way of drawing “into” the computer. The tablet is transparent as well as sensitive to the third dimension, in that it can recognize three discrete pen distances away from its surface (up to about one inch). The tablet can be used on the face of the screen (thus coincident with the displayed lines) as well as horizontally, off to the side.

Drawing by Morse Payne of The Architects Collaborative made on the IBM Cambridge Scientific Center’s 2250 and subsequently plotted on a Calcomp plotter. This drawing displays a sketchiness that is most often absent in computer displays. It is composed of tiny lines whose end points are stored in the 1130’s memory. Note that, at about the shoulder and foot, the 1130 ran out of memory locations and was unable to display the complete drawing.


The typical mechanical engineering format of top, front, and side view used in Timothy Johnson’s SKETCHPAD III. By drawing in several views the machine is never confused as to where the lines belong, but the operator is. (Drawing courtesy of IBM Systems Journal)


In computer graphics, unlike the traditional trends and more like contemporary methods, a model always exists. Regardless of how it is stored within the machine, a description of the physical form must reside in the memory. From this internal description the machine can produce a section at any point, innumerable plans, and unlimited perspectives. Though it affords prolific two-dimensional output, this internal model becomes an imposition on the dialogue. For example, when drawing a section every point must have a clearly identified depth, or else the designer must draw in several orthogonal views simultaneously. Furthermore, the designer must explicitly tag surfaces and volumes. At their present stage of development computer graphics systems demand an a priori knowledge of whether the designer is working with lines, planes, or volumes, because each requires a different reception.

In computer graphics systems the architect is obliged to work in a predetermined mode (usually volumetric) which employs predefined elements whose proportions and scale may be manipulated. Such a system was developed by Lavette Teague (1968) when at M.I.T. Teague’s system—BUILD—allows the multiple juxtaposition of parallelepipeds. Spaces are described by volumes and are attached to each other by complete or partial surface-to-surface connections. In this case the topology of the shapes is kept constant, and the proportions are manipulated. The systems try to offer comprehensive, architectural computer graphics. It does not provide for a dialogue. It is computerized.

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