Spline Curve Fitting for an Interactive Design Environment
In many graphical applications, it is necessary to build a geometrical curve model by fitting a set of data points such as the input of a digitizing tablet or a scanner. We propose an interactive spline smoothing method, particularly efficient when the data set is large, that have been implemented on a “graphic-mouse” microcomputer.
The user has to choose some parameters, such as the order of the curve and its continuity, and a spline curve is automatically fitted with as few control points as possible. By tuning the values of the different parameters, the user can compare different curves and select the most appropriate one that he can easily modify locally if necessary. The resulting curve has an analytical representation in the B-spline basis,device independent, and an approximate polygonal representation, based on the subdivision of its control polygon, whose accuracy is controlled by a parameter which can reflect the device definition. We present an algorithm to select a curve, which is pointed to with the mouse on the screen, using a hierarchical data structure, derived from the polygonal approximation.
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