A freehand interface for computer aided drawing systems based on the fuzzy spline curve identifier

This paper proposes a freehand interface for computer aided drawing (CAD) systems, which is based on an online primitive curve identification technique called fuzzy spline curve identifier (FSCI). FSCI, which has been introduced by Saga and Makino (1993), identifies a freehand curve as a sequence of curve segments, each of which is categorized into one of seven kinds of primitive curves: line, circle, circular arc, ellipse, elliptic arc, closed free curve or open free curve. The interface in this paper is built by a bottom-up approach based on the primitive curve identification. Therefore, the interface handles sufficient varieties of curves for common CAD use. The prototype of the interface is composed of three pen-based interactive user interfaces over the FSCI´s primitive curve identification functions. Experimental results from the prototype show the effectiveness of the approach to a freehand CAD interface, which allows a user to input any of the seven kinds of primitive curves simply by drawing a curve and modifying it on a small scale