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Today’s graphics systems owe their existence to an innovative graduate school project called Sketchpad

Reprinted from Byte, June 1990, pp. 380-381.

Ivan Sutherland, shown with his archetypical graphics system, Sketchpad, is considered the father of interactive graphics.
This image can be zoomedIvan Sutherland, shown with his archetypical graphics system, Sketchpad, is considered the father of interactive graphics.
Back in 1960, interactive computer graphics would have seemed like an improbable idea. In that year, computer operators typically positioned stacks of prepunched cards onto computers like the Whirlwind at MIT. The Whirlwind weighed 250 tons, powered 12,500 vacuum tubes, and filled a two-story house. But in 1960, all the elements needed for CAD to become a reality were in place.

The first element sprang from the development of the computer itself, which came in part from events surrounding World War II. In 1944, the U.S. government financed the construction of MIT’s Whirlwind computer for national defense purposes. The Whirlwind introduced the first prerequisite for CAD – a CRT capable of displaying graphics.

In 1949, the Russian explosion of an atomic bomb stimulated the U.S. to fund Project SAGE (for Semi-Automatic Ground Environment). In time, the SAGE computer linked all North American radar sites. Its operators used a hand-held photocell, or “light gun” – the precursor to the light pen – to assign intercept aircraft targets (Soviet bombers) represented symbolically on the CRT. The second piece of the CAD puzzle was in place.

The Sputnik launch of 1957 generated further interest and financial support for computer research. Researchers at MIT’s Lincoln Laboratories developed the TX-0 and later the TX-2 computer, which had twice the memory of any computer of its day. Equipped with numerous switches, knobs, a keyboard, a point-plotting display, and a light pen, the TX-2 had from the first been designed to facilitate human-machine interaction. This was the third and final element essential to the development of CAD.

The atmosphere of academic freedom at MIT allowed some nontraditional research to take place: Graduate students began playing Space War – the first computer game – on the giant TX-2 computer. The game impressed at least one of the students with the immense possibilities presented by real-time interaction with the computer. That student was Ivan Sutherland, who used the TX-2 to bring together all the elements necessary for CAD in his doctoral thesis, “Sketchpad: A Man-Machine Graphical Communication System.”

The cornerstone of Sutherland’s thesis was a film that showed him using Sketchpad on the TX-2 computer to sketch a bolt. A light pen provided the coordinates corresponding to the drawing commands entered on the keyboard. Sketchpad allowed Sutherland to recall previously drawn display primitives (e.g., circles and polygons) to the screen. He was then able to rotate, scale, copy, and erase these primitives. The light pen let him edit existing drawing entities. Smaller versions of master drawings were described as “instances” of the parent drawing. Drawings created by Sketchpad could be stored on magnetic tape. Many of the computer’s switches were assigned functions, such as move and draw. In short, Ivan Sutherland’s Sketchpad was a complete and working CAD software package.

The “Robot Draftsman,” as Sketchpad was later called, illustrated the potential of computer graphics and inspired almost all who viewed it. The idea that people no longer had to become expert programmers to use the computer effectively was novel and exciting. Now users could produce graphics in real time and observe instantaneous results. Numerous scientists chose interactive computer graphics as a career field as a result of viewing Sketchpad.

An immediate effect of Sketchpad’s influence was heavy investment in computer graphics R&D by both military and commercial organizations. Today’s CAD system has benefited from the innovation of numerous contributors. IBM, for example, provided credibility to the infant CAD industry with the announcement of the IBM 2250, which added the concept of vector CAD to computer graphics. In 1966, Lockheed-Georgia used computer graphics to create a numerically controlled machined part. Then came the Alto, an innovative stand-alone system developed at the Xerox Palo Alto Research Center in California, inspired in part by Sketchpad. (Many now say that the Alto provided the most significant advancement in computer graphics.) In 1970, Ivan Sutherland developed view clipping and perspective projection to further enhance CAD.

Sketchpad was not one isolated discovery; it was an entire methodology. Many brilliant scientists and engineers have contributed to advances in computer architecture, I/O devices, and display technology, and these contributions are still ongoing. But in bringing together the pieces for the archetypical CAD system, Dr. Ivan Sutherland set the stage for the $1.6 billion CAD industry of today. For this remarkable achievement, he is rightfully known as the “Father of Computer Graphics.”

Don Bissell

Donald Bissell is a CAD designer at the Portsmouth Naval Shipyard in Portsmouth, New Hampshire. He is also a CAD consultant and is currently working on a book on the origins of CAD. He can be reached on BIX c/o “editors.”

Your questions and comments are welcome. Write to: Editor, BYTE, One Phoenix Mill Lane, Peterborough, NH 03458.

Page added on 24th August 2005.

Copyright © 2002-2006 Marcin Wichary, unless stated otherwise.