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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. |
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
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