Reconstructing "Sketchpad" and the "Coons Patch": Toward an Archaeology of CAD

"Archaeology of CAD" is an ongoing project that examines the origins of Computer-Aided Design by bringing to life some of its pioneering technologies, which were central to re-shape design practices in the image of computation during the second half of the twentieth century. On display at SIGGRAPH will be two interactive installations from this project: the reconstructions of Steven A. Coons's "Coons Patch" and of Ivan Sutherland's "Sketchpad." Drawing from primary archives and oral sources, these interactive installations playfully revisit these transformative technologies from the 1960s, and enable visitors to approximate the experience of designing with the first Computer-Aided Design systems. Developed with computational design students at Carnegie Mellon University using present-day hardware and software languages, these reconstructions are inquisitive artifacts of historical inquiry. By evoking the embodied experience of interacting with these technologies, they shed light on the new forms of human-machine work that emerged with the rise of interactive computing during the Cold-War years, and highlight the sensual and gestural dimensions of the "computer revolution." Along with the two reconstructions, a selection of rare handwritten notes and documents by Coons, and a selection of key contractual documents between the US Air Force and MIT, are displayed to offer glimpses of the institutional and intellectual context that motivated these foundational technologies of computational design.

Described by its developer Ivan Sutherland as a "man-machine graphical communication system," "Sketchpad" allowed users to draw on a nine-inch cathode ray tube monitor using a "light-pen", a keypad, and a series of knobs. Remarkably, the system featured many of the functions of modern Computer-Aided Design systems, such as constraint-based modeling and block instantiation. Using present-day hardware and software languages, our reconstruction approximates the experience of using "Sketchpad". The image shows our interactive reconstruction of Ivan Sutherland's "Sketchpad". (Daniel Cardoso Llach in collaboration with Scott Donaldson, 2017. Photo credit: Hugh "Smokey" Dyar.)

The first reconstruction revisits the "Coons Patch," a pioneering mathematical technique to calculate curved surfaces developed in the early 1960s by MIT professor of mechanical engineering—and computer graphics pioneer—Steven A. Coons. A direct ancestor of NURBS, Coons's method was, in essence, a clever interpolation algorithm. It made it possible for early computer graphics researchers to create smooth surfaces between any four parametrically defined curves. Displayed in the phosphorescent light of CRT monitors, these "patches" were photographed, animated and circulated in both research and industry circles through books, films and research reports. They were key to demonstrate computers' potential as modeling and visualization tools with applications in a variety of fields including aeronautic, automotive and architectural design. Further, they helped trigger a fledgling computer graphics community as it formed across dispersed university and industry laboratories on both sides of the Atlantic—many of whose members came to see Coons as an inspiring, founding figure. Through a custom software and hardware interface, including a large projection, our reconstruction allows visitors to design and transform their own "patches," appreciate their geometric plasticity, and explore their underlying mathematical structure.

The second reconstruction revisits "Sketchpad," the original drawing tool of the computer age, developed by Ivan Sutherland at MIT as part of his doctoral research (which Coons advised) in 1963. "Sketchpad" was equipped with functions to save, transform and manipulate drawings in ways that extended beyond the capabilities of traditional drafting media. "Sketchpad" thus remains a milestone for both interactive computing and computer graphics almost 60 years after its development. The original "Sketchpad" featured a "light pen," a keypad and control knobs with which a user could conduct a variety of drafting operations on a 7 × 7 inch CRT monitor. Our interactive reconstruction approximates the ergonomics of the TX-2 computer terminal that Sutherland used and offers access to many of "Sketchpad's" original functions. These include drawing instantiation, scaling and the definition of geometric constraints. Our reconstruction also evokes the TX-2 interface, including a modern version of the "light pen," keypad and knobs, which enable visitors to draw in ways that evoke Sutherland...