In this paper, the relation between difference algorithms and the repr
esentation of parametric curves is studied in detail. It is shown that
stationary difference algorithms could generate a class of curves, th
e so-called D-curves, that are suitable in free-form curve and surface
modelling and design. The corresponding D-Bezier curves are also cons
tructed and their properties studied. This generalizes our findings in
the study of a simple three-term difference algorithm in which it has
been concluded that a simple three-term difference algorithm could ge
nerate both conic curves, general monomial curves, and exponential spi
ral curves. (C) 1998 Elsevier Science Ltd. All rights reserved.