If to err is human, to design corrective systems is all the more so. When in 1962 Ivan Sutherland designed the first drafting program that would allow us, amongst other things, to draw better circles, he was in many ways simply providing an update to Leon Battista Alberti’s circle-drawing system issued some five hundred years earlier in De Pictura. Crucially, in both, one does not have to be able to draw a circle to draw a circle. Sutherland, under Claude Shannon’s wily guidance, radically augmented the corrective capacity of the algorithm at work in an exercise that is not difficult for machines but exceptionally tricky for humans. Whereas Alberti devised a way to draw curved perfection by erecting an approximating join-the-dots scaffold, Sutherland did away with the stepping-stone dots altogether.
Sutherland’s extraordinarily prescient and elegant program, Sketchpad: a Man-machine Graphical Communication System, inherited everything the US air defense system SAGE had recently invented, and added almost everything else required to make the CAD interface through which so much design is now thought, developed and represented, including the physical mechanics of drawing something—a cursor and hand-held input, first in the form of a touchscreen “light pen” that would later become a mouse—as well as deleting it. By never registering the wobble of the hand-drawn circumference on screen, Sutherland sought to correct error before it could even be recognized by the human eye. Whereas Alberti’s armature gently corrected the erratic radius of our hand, Sketchpad effectively ignores it and uses the light pen’s location only to decide how much arc to draw.
To draw a circle we place the light pen where the center is to be and press the button ‘circle center,’ leaving behind a center point. Now, choosing a point on the circle (which fixes the radius) we press the button ‘draw’ again, this time getting a circle arc whose angular length only [and not its radius] is controlled by light pen position.
Sketchpad’s design incorporated other strategies for opportunistic correction in the form of prediction using “pseudo-gravity,” whereby the light pen snaps onto any line it gets too close to. That is, the software “corrects” us through the assumptions of approximation. The desires of this corrective remit are not limited to the question of the drawing and representation; Sutherland redesigned not only the drawing, but by virtue of a Sketchpad drawing being a “model of the design process,” the design process itself. The automatic correction of drawings inaugurated a design process whose legacy is now such that it finally no longer needs a designer in the sense that disegno once imparted. Nor does it need input exactitude from us, which is not to say the product is rough, approximate or in any sense a “sketch.” On the contrary, the corrective nature of what is essentially the beginning of predictive programing allows you to be “quite sloppy,” as Sutherland explains, and still “get a precision drawing out at the same time.” When the light pen decides the hand is simply being sloppy and is close enough to a line to snap onto it, the time for doubt or hesitation is foreclosed. Sketchpad signifies, tout court, the end of doubt; predictive programming as preemptive correction.
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