Smooth curves (parametric curves: P = P(t) = (p sub 1 (t), ..., p dim (t)); each p sub i (t) is a piecewise polynomial function), based on a theory of b splines are described. Basic algorithms for the calculation of piecewise polynomial functions (pp functions), using b splines, are given. The theory is described in close connection with computer programs for plotting pp functions and curves. Local adaption to a data point, cyclic curves, and anticyclic continuations are main features. A complete computer program for plotting parametric curves is listed. An algorithm for dynamically adapting stepsize to curvature is also shown.
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