September 5, 2018

Sketchpad of Ivan Sutherland: This Amazing Footage Shows What CAD Looked Like 55 Years Ago!

In January, 1963, Ivan Sutherland, a PhD candidate at MIT, submitted his thesis, titled “Sketchpad: A Man-Machine Graphical Communication System,” describing his work in creating what is now recognized as one of the very first interactive computer-aided design (CAD) systems.

Ivan Sutherland on MIT Lincoln Labs’ TX-2 computer.

Sketchpad ran on MIT Lincoln Labs’ TX-2 computer. It was, at the time, one of the biggest machines in the world, with 306 kilobytes of core memory. It differed from most contemporary computers, in that it was designed to test human-computer interaction. In addition to the standard complement of I/O devices, the TX-2 had programmable buttons for entering commands, an oscilloscope/video display screen (addressable to 1024×1024 pixels), a light pen for input, and a pen plotter for output. It was, in a way, the first personal computer, albeit one that took up an entire building.

This video is a TV show made about the software Ivan Sutherland developed in his 1963 thesis at MIT's Lincoln Labs, Sketchpad.


Unlike earlier computer applications, which were batch oriented, Sketchpad was interactive. Using the light pen and input buttons, you could draw directly on the screen, using a crosshair cursor. The program supported points, line segments, and arcs as basic elements, but allowed these to be saved into master drawings, which could be copied or instanced. This facility was used to create alphanumeric character glyphs, and electrical schematic symbols.

One thing that made Sketchpad really stand out was its constraint management subsystem. It not only supported explicit constraints, added to entities after they were drawn, it supported implicit constraints, created as entities were drawn. For example, if you started to draw a line, and brought the cursor close to the endpoint of another line, it would snap to that endpoint. And it would remember that the two lines were connected. If, while editing, you moved one line, the other line would move with it.


Sketchpad included 17 different types of constraints, including vertical, horizontal, perpendicular, coincident, parallel, aligned, equal size, and more. These native (or “atomic”) constraints could be combined, to create more complex relationships. Sketchpad even allowed the visual display of constraints on screen, using icons (symbols) to represent each type.

With the constraint system, it was possible to loosely sketch a shape, then add geometric and topological relationships to modify it into the exact shape you needed. It was even possible to use constraints to do structural analysis of lattice trusses, such as might be found on cantilever and arch bridges.


Visually, Sketchpad was surprisingly interactive. It supported rubberbanding when drawing or editing entities (so the entities would stretch as you moved the cursor.) It supported dynamic move, rotate, and scale of entities (meaning that they moved, rotated, and scaled as you moved the cursor.) It not only supported zoom and pan (dynamically, of course), but did so transparently—even when you were in the midst of another drawing or editing operation.

Sketchpad was designed to be extensible, with provision for adding both new graphical element types, and new constraint types. Shortly after Sutherland submitted his Sketchpad thesis, Timothy E Johnson submitted his Masters thesis describing Sketchpad III, a 3D version of the program. About the same time, Lawrence G. Roberts submitted his PhD thesis, where he had added support to Sketchpad for 3D solids, including assemblies and real-time hidden line removal.

Timothy E. Johnson

Sketchpad pioneered some of the most important concepts in computing, including the graphical user interface, non-procedural programming, and object-oriented programming. If you use a computer or smart phone, you’re using technology pioneered by Sketchpad.

Sutherland didn’t rest on his laurels after Sketchpad. He went on to run ARPA (the predecessor of DARPA.) He co-created the first virtual reality and augmented reality head-mounted display. He co-founded Evans and Sutherland, where he did pioneering work in the field of real-time hardware, accelerated 3D graphics, and printer languages. He was a Fellow and Vice President at Sun Microsystems. He taught at Harvard, University of Utah, and Caltech. Now, at the age of 80, he is heading up research in asynchronous computing at Portland State University.

(via Design World)




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