Standard Geometry Realization In The Sketching System

Freehand drawing, known as sketching, is a common expression in the conceptualdesign phase to express design intention and provide a platform of unfolding designthinking and expansion creative design work by designers. With the improvement ofhardware and software in computer, many institutes have investigated the sketchingsystems based on human-computer interaction technology at home and abroad. Thesketching systems have practical significance to realize the transformation from2D to3Din the conceptual design phase, which save the time and the cost of development. However,most of studies based on the all hand-painted method, which can cause the ambiguousinformation easily in the transformation. Especially in the automotive industry, higherrequirements are needed. The ambiguous information would hander the process of designand waste the time of product development. This article proposed a kind of geometrystandardization based on the3D sketching to eliminate this ambiguous information in theprocess from2D to3D in the sketching system development. The geometries for thestandardization include the2D graphics such as straight line, circle, ellipse, circular arc,elliptical arc, parabola, semicircle, sector, polygon, combination of lines and curve, and the3D graphics such as cone, cylinder, sphere, etc. The study has been applied in AutoSketch,a free-hand sketching system, to support the standard geometry sketching. The details areas follows:1) The paper has analyzed and digested the related literatures from home and aboard,summarized techniques and theoretical methods of the relevant prototype systems, andfocused on discussing and studying the technologies and methods of sketching recognition,shape matching and sketching reconstruction. Based on those theories, this paper hasproposed the geometry standardization of three-dimensional freehand sketching in theautomotive styling. 2) It has introduced the procedure and method of data processing in the geometrystandardization, and given out the research contents and the overall structures. Thepre-processing method of strokes before the segmentation has also been discussed here.3) The identification and fitting algorithms of the geometric elements have beendeveloped including line, circle, oval, circular arc, elliptical arc, parabola and free-formcurves.4) The identification and fitting algorithms of2D geometris have also developedmainly for the arbitrary multi-stroke polygons. It described how to extract the featuresaccording to the position relationship of the elements. According to the graphic featurematching, this paper has proposed some specific methods and procedures for them. Thegeometries are output through the standardization.5) The recognition and fitting algorithms of3D geometries has been investigated forthe completed free-hand sketched geometries. As a result, the recognition and fittingmethod of the semi-free-hand sketched geometries has been proposed in the paper throughthe analysis of advantages and disadvantages to the former. The research shows that thelatter is more convenient for users.6) The paper has discussed the arbitrary modification of geometries during sketchingand standardization. A sketched geometry can be modified in any way by the recognitionand human-computer interaction.