This article is devoted to motion-based techniques for generating NURBS sur
faces. We present a highly accurate approximation of the rotation-minimizin
g frame (RMF) of a space curve that leads to a RMF-based scheme for rationa
l sweep surface modeling. Further we study envelopes of moving developable
surfaces emphasizing the special cases of a moving cylinder or cone of revo
lution. (C) 1999 Elsevier Science Ltd. All rights reserved.