Research On Stroke Semantics Of Conceptual Design Sketch And Its Application

During the product conceptual design stage, designers often draw conceptual sketches to record their own thinking ideas. The conceptual sketch is not only a design expression tools but also an important media of product innovations. Traditional CAD tools need user to input accurate data, but design thinking idea is regarded as moment inspiration and fuzzy information. Using traditional CAD tools can interrupt or delay design process easily. Due to the conflict between the current CAD softwares and thinking ideas, there is not an integrated CAD system which can be used well at the conceptual design stage. Hence in order to make thinking ideas close to the follow-up engineering design, this paper primarily attempts to explore the stroke semantic interpretations of conceptual design sketch, especially online line drawing strokes as an important research object.Conceptual sketches contain many different kinds of strokes. Due to the fact that strokes record a lot of design thinking ideas, the semantic features are explored from different strokes. The intention of this work is how to translate ambiguous information of sketches into CAD data, according to design thinking ideas. Besides, we propose a methodology to sketch online 3D strokes, which suits designer's sketch habit more. Specifically, the following are the main contents and contributions of this paper:First, based on the conventional habits, this paper depicts stroke semantic interpretations from expression skills and 2D geometric features. On this basis, the stroke recognition and beautification methods for reducing the ambiguity of sketches is presented, including: estimating corners from single stroke, fitting single stroke for 2D parametric curves based on least-squares, merging overtracing strokes, and extracting the graph topology from profile & form line drawing strokes. Furthermore, the related programme is implemented under above methods.Secondly, sketch perspective semantics under perspective projection way are studied, and a basic method was presented that drawing environment information was given from cube line drawings, including perspective type decision, projection parameter and 3D cube actual scale calculation, etc. As the strokes semantics spread from 3D geometrical and topological attributes, the relation between perspective projection parameter and 3D free transformation is presented in this chapter. Third, under the product conceptual innovation domain, the related work of 3D online sketch techniques is summarized. In addition, this paper propose a 3D online sketch technique based on different stroke semantics, including the 3D stroke drawing methods of contour lines, form lines, shading lines. Based on the semantic characteristics, the prototype system supported 3D online sketch technique is built, and the related algorithms are verified.The final chapter of this paper summarizes our researches and innovations, and discusses some directions of future research work.