A scheme is described for interactively modifying the shape ofconvexity preserving planar interpolating curves. An initial curve isobtained by patching together rational cubic and straight line segments.This scheme has, in general, geometric continuity of order2(G2 continuity) and preserves the local convexity of the data. Amethod for interactively modifying such curves, while maintainingtheir desirable properties, is discussed in detail. In particular, attentionis focused upon local changes to the curve, while retainingG2 continuity and shape preserving properties. This is achievedby interactive adjustment of the Bezier control points, followed byautomatic adjustment of the values of weights and curvatures in aprescribed manner. A number of examples are presented.
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