Weight-based shape modification of NURBS curves

We address the problem of how to perform prescribed shape modification of N URBS curves merely by the modification of the weight of some of their contr ol points. As is known, NURBS curves can be considered as central projectio ns of nonrational B-spline curves. Making use of the property that there is an infinite number of nonrational B-spline curves the central projection o f which is a given NURBS curve, we provide a weight-based shape modificatio n method by means of which one can prescribe not only the new position of a n arbitrary chosen point of a plane NURBS curve but the tangent direction a s well. (C) 1999 Elsevier Science B.V. All rights reserved.