Ivan Sutherland's Sketchpad is one of the most influential computer programs ever written by an individual. In November of 1961, Ivan Sutherland, doctoral candidate in electrical engineering at the Massachusetts Institute of Technology (MIT) and computer programmer extraordinary, sat engrossed at the console of the TX-2 computer in the basement of M.I.T.'s Lincoln Laboratory. He was at work on his dissertation project, a computer drawing program he called Sketchpad. The name derived from the proclivity of engineers to rough out an idea on a scrap of paper, then gradually refine it by making innumerable revisions.

		Sutherland was convinced that he could turn the computer into a superior tool for this process. Sutherland was only one of many researchers captivated by the interactive possibilities of the TX-2, so he had to scramble for a share of the computer's precious time, even if that meant getting out of bed at two or three in the morning. Sutherland had first decided to write a computer graphics program in April of 1961. The preceding winter, while working on other projects, he had become familiar with the TX-2 and noticed that its design made drawing convenient. Besides the light pen, it had a CRT screen and enough memory to hold 280,000 bytes, a prodigious capacity at the time. Furthermore, the TX-2 could be modified with little difficulty, and Sutherland requested the addition of a bank of push buttons. Realizing that computer graphics could have significant applications in engineering and design, Sutherland bent his efforts toward increasing the operator's control of the image on the screen.
In 1958 Ivan Sutherland, began working at Lincoln Labs with the TX-2 to manipulate pictures.

In contrast, Sketchpad promised to turn the computer into a tool that anyone might use. Even at this early stage, the program allowed someone with no programming experience to solve complex engineering problems through the use of computer graphics. In effect, Sketchpad translated the operator's wishes into the computer's binary language and displayed the machine's response instantly, in real time. Sutherland's work at M.I.T. would ultimately be viewed as a turning point in the history of computer graphics. Before Sutherland and Sketchpad, most of the graphics applications of computers were for military purposes. After Sutherland, computer graphics was used increasingly as a tool for industrial engineering and design, mainly in the auto and aerospace industries but gradually in other as well.
		The 1963 cover of the unclassified Technical Report on Sketchpad.

Work on Sketchpad begun in the fall of 1961. An early Success was to make a small cross displayed on the computer monitor follow the light pen around the screen. The cross provided a signal for the light pen to detect and lock onto, and served as the starting point for a drawing. Sutherland had to program a score of other details before Sketchpad could draw a simple straight line. For example, he wrote instructions to the computer that interpreted pushing a button as an order to remember the coordinates of the cross's position at that instant.

		The light pen is a hand held photocell which will report to the computer whenever a spot on the display system falls within its small field of view. The housing for the photocell is about the size of a fountain pen and is manipulated much as a pen or pencil, hence the name. Many different varieties of light pens have been built, including large cumbersome ones in the days before miniaturization, to be replaced by transistorized versions, and recently by fiber optic pens connected by a fiexible light pipe to a photocell mounted inside the computer frame. The particular pen used for the Sketchpad system consists of a photodiode and transistor preamplier mounted in the pen housing and connected to the computer by a length of small coaxial cable.
Sketchpad photodiode & transistor light pen.

The ability to put motion into the drawings suggests that it would be exciting to try making cartoons. The capability of Sketchpad to store previously drawn information on magnetic tape means that every cartoon component ever drawn is available for future use. If the almost identical but slightly different frames that are required for making a motion picture cartoon could be produced semiautomatically, the entire Sketchpad system could justify itself economically in yet another way. One way of cartooning is by substitution. For example, the girl “Nefertite” can be made to wink by changing which of the three types of eyes is placed in position on her otherwise eyeless face. Doing this on the computer display has amused many visitors. A second method of cartooning is by motion. A stick figure could be made to pedal a bicycle by appropriate application of constraints. Similarly, Nefertite's hair could be made to swing. This is the more usual form of cartooning seen in movies.
		This cartoon can be made to wink by changing which of the three types of eyes is placed in position.

		A Sketchpad drawing would consist of points, lines and arcs linked together to form objects. Once created, any object, or shape, could be enlarged, reduced or rotated on the screen. It could be stored in a library of shapes and recalled for future use. It could be duplicated and the copies arranged to generate a new shape. With these rules, a complex drawing of a bridge or an automobile could be created as a hierarchy of simpler components, each of which could be altered and moved around on the screen. With a basic bridge shape, the components are made to behave like a bridge beam. One can then test with different loading setting and supports to see the effects of on cantilever and arch bridge types do. The numbers show the forces in the different components as computed by Sketchpad.
Various loading conditions on a vector graphic bridge.

Electrical engineers are, of course, interested in making circuit diagrams. It is not surprising that Sketchpad should be applied to this task. Unfortunately, electrical circuits require a great many symbols which have not yet been drawn properly with Sketchpad and are not therefore in the library. After some time is spent working on the basic electrical symbols it may be easier to draw circuits. So far, however, circuit drawing has been a big flop. You can see in the figure that the more complicated circuits are made up of simpler symbols and circuits. It is very difficult, however, to plan far enough ahead to know what composits of circuit symbols will be useful as subpictures of the final circuit. The simple circuits shown were compounded into a big circuit involving about 40 transistors. Including much trial and error, the time taken by a new user (for the big circuit not shown) was ten hours.
		The circuits are parts of an analog switching scheme.

The circuit experience points out the most important fact about computer drawings. It is only worthwhile to make drawings on the computer if you get something more out of the drawing than just a drawing. If we had a circuit simulation program connected to Sketchpad so that we would have known whether the circuit we drew worked, it would have been worth our while to use the computer to draw it. We are as yet a long way from being able to produce routine drawings with the computer.

		The methods outlined in this report generalize nicely to three dimensional drawing. In fact, work has already been begun to make a complete “Sketchpad Three” which will let the user communicate solid objects to the computer. A forthcoming thesis by Timothy Johnson of the Mechanical Engineering Department will describe this work. When Johnson is finished it should be possible to aim at a particular place in the three dimensional drawing through two dimensional, perspective views presented on the display. Johnson is completely bypassing the problem of converting several two dimensional drawings into a three dimensional shape. Drawing will be directly in three dimensions from the start. No two dimensional representation will ever be stored.
The 1964 TV program on Ivan Sutherland's Sketchpad at MIT.

Work is also proceeding on direct conversion of photographs into line drawings. Roberts reports a computer program able to recognize simple objects in photographs well enough to produce three dimensional line drawings for them. Roberts is storing his drawings in the ring structure so that his results will be compatible with the three dimensional version of Sketchpad.

Later in 1963, Sutherland made a movie of Sketchpad in operation. He showed it around the M.I.T. campus to students and teachers, soliciting their opinions. Copies of the film made their way to other campuses. David Evans, who later joined Sutherland in founding a computer graphics company, was then a computer science and electrical engineering professor at the University of California at Berkeley. He remembers that the Sketchpad film was "like an underground movie. There were lots of copies around. It was immediately obvious that this was beyond what anyone else had done.

The Sketchpad film shown at the spring joint Computer Conference in Detroit in 1963, where it fired the imaginations of those who had not yet seen it. Andries van Dam, later chairman of the Brown University computer science department, was one of them. He decided "on the spot that graphics was going to be my research area." Van Dam shared Sutherland's opinion that Sketchpad's most immediate value lay in designing new products. Nevertheless, the reaction from companies was disappointing at first. Industry in general seemed to have something of a blind spot when it came to computer graphics, regarding the idea as a bit of unusable electronic razzmatazz. In 1968, he alongwith Evans founded Evans & Sutherland in Salt Lake City.

1963 Ivan Sutherland, SKETCHPAD, A Man-Machine Graphical Communication System at MIT