GEOMETRIC CONTROL OF G(2)-CUBIC A-SPLINES

A-splines are piecewise algebraic curves, constructed in a control pol ygon that is a sequence of triangles meeting at the vertices, The are in a given triangle is a cubic segment that joins these vertices and i nterpolates also the slope and curvature at each endpoint. This are in each triangle is controlled by three other shape handles: an interior point that is interpolated, the slope at the interior point, and a te nsion parameter, The individual arcs can never be singular and are alw ays convex. An inflection point of an A-spline must be placed at a jun ction point. (C) 1998 Elsevier Science B.V.