| The computer supported sketching technology, as an extension and important development of Computer Aided Design (CAD) technology, has been bridging the gap between the freehand sketching on paper and CAD, so as to make CAD more perfect by supporting the whole process of product design. And it is also one of the key techniques of Computer Aided Industrial Design (CAID). This dissertation, aiming at the product conceptual design stage, makes a profound and systematic research on the theory and method of computer supported intelligent sketching, especially the key techniques, including the pen-based gesture interface and sketching, sketch recognition and interpretation, and sketch-based geometric modeling. Finally a much practical sketching tool, Intelligent Sketching based Innovative Design: ISID, is implemented. The main research contents and achievements are articulated as follows:(1) Sketch studies and the computer supported intelligent sketching technologyFirstly, the conventions and behavior characters of sketching, and the relations among design tasks, thinking (intensions) and sketching, are studied and summarized. Then the computer supported sketching mode is given. Based the above theory, a whole computer supported intelligent sketching technology system, as the principle of the implementation of intelligent sketching, is built, including five key techniques.(2) Pen-based sketch interfaceThe sketch interface, including stroke-based gesture interface and pen-based sketching technique, can provide users with the freedom of sketching on paper without worry about the rigorous geometric attributes and integrality. Through the application of the gesture-based interaction technique, the complex and clumsy interaction operations are replaced by simple strokes. The gesture interface technology consists of gesture recognition, gesture design and implementation of gesture interface. For making gesture recognition more robust, the grid-coding based recognition algorithm is used and the matching algorithm is improved. In addition, a primary set of gestures for sketching is proposed.(3) Recognition of Pen-based sketchesAs the core technique of intelligent sketching, the sketch recognition is realized in the dissertation through three steps: on-line stroke recognition, Sketch Beautification from the geometric view, and Sketch Understanding from the semantic view. By this way the ability of recognizing sketch is improved, and the illegibility and uncertainty of sketch are dissolved step by step.The on-line stroke recognition algorithm can recognize the rough strokes and transform them into three basic geometric line-elements, including straight line, arc and B-Spline. Different recognition methods, such as the improved Freeman Chain Code, are used for different types of line. Sketch Beautification, including line-elements spatial relations analysis and constraints adding, is performed through a KBS (Knowledge Based System) with a blackboard. Further a Sketch Grammar Knowledge Base is built on the research of the line-elements relation. Based on the design intention from the sketch context, the possible spatial or geometric relations among the line-elements are assured, and the related constraints are fixed on the fines. Then disorder sketch is arranged regularly. But for the transformation from scattered line-elements to geometric object with certain design concept, the domain knowledge is needed. Sketch Understanding, based on domain knowledge, is still performed through a KBS. In this dissertation, product elements pattern class and geometric feature class are defined, and a Product Domain Knowledge Base is built, including product elementspattern rules database, geometric features database, and product template for elements mapping. Based on the pattern matching and constraint adding mechanism, the sketch is interpreted and regularized.(4) Sketch-based product modelingThe sketch-based product modeling techniques, including the integration of 2D sketching and solid...
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