We investigate the functions of drawing in design and how, based on these functions, a computational sketching
environment might support design reasoning. Design, like all problem solving activities, involves reasoning--making
decisions, expressing ideas, verifying and evaluating proposals, and ultimately, taking action. For designers, drawing is
a vehicle for design reasoning, and therefore the spontaneous marks made on paper during sketching form a partial
record of the designer's thinking. Most designers sketch early design ideas with a pencil on paper: sketching is still the
quickest and most direct means to produce visual representations of ideas. The ambiguity of free hand sketching allows
multiple interpretations and thus stimulates the production of more design alternatives. The linked acts of drawing and
looking invite designers to recognize new interpretations of the alternatives they propose. By drawing and looking,
designers find visual analogies, remember relevant examples, and discover new shapes based on previously
unrecognized geometric configurations in their sketches.

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