João Paulo Pereira

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Throughout the last decade many approaches have been made to the problem of developing CAD systems that are usable in the early stages of product ideation. Although most of these approaches rely on some kind of drawing paradigm and on the paper-and-pencil metaphor, only a few of them deal with the ambiguity that is inherent to natural languages in general(More)
CAD systems have yet to become usable at the early stages of product ideation, where precise shape definitions and sometimes even design intentions are not fully developed. To overcome these limitations, new approaches, which we call Calligraphic Interfaces, use sketching as the main organizing paradigm. Such applications rely on continuous input modalities(More)
This paper describes error handling and ambiguity in a class of applications organized around drawing and sketching, which we call Calligraphic Interfaces. While errors and imprecision are unavoidable features of human input, these have long been considered nuisances and problems to circumvent in user interface design. However, the transition away from(More)
Sketch-based interfaces can provide a natural way for users to interact with applications. Since the core of a sketch-based interface is the gesture recognizer, there is a need to correctly evaluate various recognizers before choosing one. In this paper the authors present an evaluation of three gesture recognizers: Rubine's recognizer, CALI and the $1(More)