The very beginning of the digital representation – Ivan Sutherland Sketchpad

Ivan Sutherland is considered by many to be the creator of Computer Graphics and an Internet pioneer. Starting with his Ph.D. thesis, named Sketchpad, which is one of the most influential computer programs ever written by an individual, Sutherland has contributed numerous ideas to the study of Computer Graphics and Computer Interaction. He introduced concepts such as 3-D computer modeling, visual simulations, computer aided design (CAD), virtual reality, etc.

His first computer experience was with the famous computer Simon of Edmund Berkeley. Ivan’s first big computer program was to make Simon divide. To make division possible, he added a conditional stop to Simon’s instruction set. This program was a great accomplishment, it was the longest program ever written for Simon, a total of eight pages of paper tape. Ivan and his brother Bert even met Berkeley and were inspired to envision new avenues for programming.

Sutherland went on the study at Carnegie Mellon University, where he earned a Bachelor’s degree in Electrical Engineering and then went on to earn a M.S. also in Electrical Engineering from the Caltech (California Institute of Technology). For his Ph.D., Sutherland went to MIT (Massachusetts Institute of Technology) were he studied under Claude Shannon and Marvin Minsky and developed his revolutionary thesis, Sketchpad, A Man-Machine Graphical Communication System, the first Graphical User Interface.

Sketchpad was influenced by the conceptual Memex of Vannevar Bush, as it was envisioned in his fundamental paper “As We May Think”. Sketchpad, in turn, influenced Douglas Engelbart’s NLS (oN-Line System).

Sketchpad ran on the Lincoln TX-2 computer, an innovative machine designed in 1956 (it had a large amount of memory for its time: a vacuum-tube-driven core of 64K words, a faster, transistor-driven core of 4K words, a paper-tape reader and could also use magnetic tape as auxiliary storage.) TX-2 was an “on-line” computer (at that time most computers would run “batches” of jobs and were not interactive), used to investigate the use of Surface Barrier transistors for digital circuits. TX-2 included a nine inch CRT and a light pen which first gave Sutherland his idea. He imagined that one should be able to draw on the computer. Sketchpad was able to do just this, creating highly precise drawings, and also introduced important innovations such as memory structures to store objects and the ability to zoom in and out.

The Sketchpad uses drawing as a novel communication medium for a computer. The system contains input, output, and computation programs which enable it to interpret information drawn directly on a computer display. It was a general purpose system and has been used to draw electrical, mechanical, scientific, mathematical, and animated drawings. Sketchpad has shown the most usefulness as an aid to the understanding of processes, such as the notion of linkages, which can be described with pictures. Sketchpad also makes it easy to draw highly repetitive or highly accurate drawings and to change drawings previously drawn with it.

A Sketchpad user sketches directly on a computer display with a “light pen.” The light pen is used both to position parts of the drawing on the display and to point to them to change them. A set of push buttons controls the changes to be made such as “erase”, “move”, etc.

Information sketched can include straight line segments and circle arcs. Arbitrary symbols may be defined from any collection of line segments, circle arcs, and previously defined symbols. A user may define and use as many symbols as he wishes. Any change in the definition of a symbol is at once seen wherever that symbol appears.

Sketchpad stores explicit information about the topology of a drawing. If the user moves one vertex of a polygon, both adjacent sides will be moved. If the user moves a symbol, all lines attached to that symbol will automatically move to stay attached to it. The topological connections of the drawing are automatically indicated by the user as he sketches. Since Sketchpad is able to accept topological information from a human being in a picture language perfectly natural to the human, it can be used as an input program for computation programs which require topological data, e.g., circuit simulators.

Sketchpad itself is able to move parts of the drawing around to meet new conditions which the user may apply to them. The user indicates conditions with the light pen and push buttons. For example, to make two lines parallel, he successively points to the lines with the light pen and presses a button. The conditions themselves are displayed on the drawing so that they may be erased or changed with the light pen language. Any combination of conditions can be defined as a composite condition and applied in one step.

It is easy to add entirely new types of conditions to Sketchpad’s vocabulary. Since the conditions can involve anything computable, Sketchpad can be used for a very wide range of problems. It has been used, for example, to find the distribution of forces in the members of truss bridges drawn with it.

Sketchpad drawings are stored in the computer in a specially designed “ring” structure. The ring structure features rapid processing of topological information with no searching at all. The basic operations used in Sketchpad for manipulating the ring structure are described.

Sutherland contribution is not the revolutionary Sketchpad, however. In 1964 he replaced J. C. R. Licklider as the head of the US Defense DARPA’s Information Processing Techniques Office (IPTO), the motive force of Internet.

In 1968, together with his student Bob Sproull, Sutherland created the first virtual reality and augmented reality head-mounted display system, named The Sword of Damocles.

Among his students were the famous computer scientist Alan Kay, Henri Gouraud (who devised the Gouraud shading technique), Frank Crow, who developed antialiasing methods, etc.

His company Evans and Sutherland (founded together with his friend David Evans) has done pioneering work in the field of real-time hardware, accelerated 3D computer graphics, and printer languages. Former employees of company included the future founders of Adobe (John Warnock) and Silicon Graphics (Jim Clark).

Sutherland received the Turing Award from the Association for Computing Machinery in 1988 for the invention of Sketchpad. He is a member of the National Academy of Engineering, as well as the National Academy of Sciences among many other major awards.

Source: www.history-computer.com