It is argued that a significant feature which acts as a disincentive against the adoption of CAAD systems by small private architectural practices, is the awkwardness of communicating with computers when compared with traditional drawing board techniques. This consideration, although not perhaps the dominant feature, may be mitigated by the development of systems in which the onus of communicating is placed on the machine, through the medium of an architect's sketch plan drawing. In reaching this conclusion, a design morphology is suggested, in which the creative generation of building designs is set in the context of the development of a 'data-base' of information which completely and consistently describes the architect's hypothetical building solution. This thesis describes research carried out by the author between 1981 and 1984, and describes the theory, development and application of algorithms to interpret architect's sketch plan drawings, and hence permit the encoding of building geometries for CAAD applications programs.

For the first two decades of their history, computers were text only. With the exception of a few experimental military systems, they did not feature any interactive graphics displays. Then, in the 1960's, while designing the first interactive graphical computer-aided design system, a young American electrical engineer named Ivan Edward Sutherland created the framework for modern computer graphics. The system was called Sketchpad, and it was created in a facility dedicated to developing and expanding the United States' defense system after the end of World War Two. Initially, however, Sketchpad was not designed for military purposes. It was the product of a culture of experimentation with the 'new' technology of the computer, and proceeded from an attempt to not only utilize the computer, but also to communicate with it. Sutherland never claimed to have a vision for the future of computer science, or for the influence that Sketchpad may subsequently have had within the development of computer graphics. While he proposed varied applications for the use of Sketchpad, Sutherland never considered the program in relation to the wider context of architectural studies. Unlike traditional architectural drawing tools that realize architectural imagination through line drawing, computer-aided architectural design programs began to use line drawing to also establish communication with the computer. Sketchpad and the computer-aided architectural design programs that evolved from it helped to facilitate the growing symbiotic relationship between the architect and the computer. Through the new field of computer drawing, the drafter began to be able to 'converse' with the computer, and crucially, through the Sketchpad window, it began to seem as if the drafter was speaking face-to-face with another person. Sketchpad's window employed the same cathode-ray tube monitor developed for the television in the 1940's, and was used to illustrate a winking girl that Sutherland identified in his dissertation as 'Nefertiti'. Sutherland's 'Nefertiti winked at him from the other side of the computer window, and seemingly came alive under his touch. Through Sketchpad's window, 'Nefertiti' effectively suggested that this new machine – the computer – was an active partner in the design process. / Ph. D.