Abstract Based on geometric features and hybrid features, the fuzzy recognition methods of online freehand sketching are discussed. The fuzzy features and corresponding extraction methods of geometric primitives are introduced, and a general fuzzy membership function is designed by analyzing the triangle membership function. The possibilities of geometric primitives which the stroke belongs to are obtained through numerous experiments. The system supplies the human-computer interactive determinant of the stroke through cutting the value of membership function. If necessary, the designer can help the system make the proper inference when either wrong choice is made by the system, or plural possibilities are analyzed. By the methods, designers' intentions can be inferred and input sketches can be interpreted into more exact 2D geometric primitives, including straight line, polyline, circle, circular arc, ellipse, elliptical arc, hyperbola and parabola. The effectiveness of the algorithm is demonstrated preliminarily by experiments. It lays the foundation for 3D object recovering and conceptual design of freehand sketching.
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2008, Vol. 21 
