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Generative specifications have been used to systematically codify established styles in several design fields including architecture and product design. We examine how designers explore new designs in the early stages of product development as they manipulate and interpret shape representations. A model of exploration is proposed with four types of shape descriptions~contour, decomposition, structure, and design! and the results of the exploration are presented. Generative rules are used to provide consistent stylistic changes first within a given decomposition and second through changing the structure. Style expresses both the analytical order of explanation and the synthetic complexity of exploration. The model of exploration is consistent with observations of design practice. The application of generative design methods demonstrates a logical pattern for early stage design exploration. The model provides the basis for tools to assist designers in exploring families of designs in a style and for following new interpretations that move the exploration from one family to another.

The process of sketching can support the sort of transformational thinking that is seen as essential for the interpretation and reinterpretation of ideas in innovative design. Such transformational thinking, however, is not yet well supported by computer-aided design systems. In this paper, outcomes of experimental investigations into the mechanics of sketching are described, in particular those employed by practicing architects and industrial designers as they responded to a series of conceptual design tasks. Analyses of the experimental data suggest that the interactions of designers with their sketches can be formalised according to a finite number of generalised shape rules. A set of shape rules, formalising the reinterpretation and transformations of shapes, e.g. through deformation or restructuring, is presented. These rules are suggestive of the manipulations that need to be afforded in computational tools intended to support designers in design exploration. Accordingly, the results of the experimental investigations informed the development of a prototype shape synthesis system, and a discussion is presented in which the future requirements of such systems are explored.

Abstract. This paper argues that sequences of exploratory drawingsconstructed by designer's movements and decisions -trace systematic and logical paths from ideas to designs. This argument has three parts. First, sequences of exploratory sketches produced by product designers, against the same task specification, are analyzed in terms of the cognitive categories of reinterpretation, emergence and abstraction. Second, a computational model is outlined for the process of exploration through drawing and third the model is applied to elucidate the logic in the sequences of exploratory sketches examined earlier.

Throughout the history of CAD, a variety of interfaces have been employed with the aim of supporting designers' construction and manipulation of digital models. This paper explores the potential of eye tracking as a CAD interface, and presents a prototype that uses collected gaze data to support shape exploration in a two-dimensional vectorbased sketch editor. The eye tracking interface uses the visual interactions of users to identify interpretations of constructed shapes, according to recognised parts identified using methods from shape grammar research. It can therefore be argued that it supports construction and manipulation of shapes according to user intent. The prototype has been evaluated in a user study where design students carried out controlled shape exploration exercises which involved interpretation and manipulation of shapes. In the paper, key concepts of eye tracking methodology are introduced; the methods used to implement the eye tracking interface are described; and the user study and its outcomes are reported. The results are positive and indicate the potential for eye tracking as an interface for supporting shape exploration in CAD. Research Highlights• Explores the potential of eye tracking as an interface for computer aided-design• Describes methods for inferring user intent with respect to digital shape manipulation, based on gaze data • Presents a prototype eye tracking interface that supports dynamic shape interpretation in a vector-based sketch editor • Reports the outcomes of a user study that evaluates how successful the eye tracking interface is at inferring users' intent with respect to shape manipulation