In this paper we extend the classical notion of offset to the concept
of generalized offset to hypersurfaces. In addition, we present a comp
lete theoretical analysis of the rationality and unirationality of gen
eralized offsets. Characterizations for deciding whether the generaliz
ed offset to a hypersurface is parametric or it has two parametric com
ponents are given. As an application, an algorithm to analyse the rati
onality of the components of the generalized offset to a plane curve o
r to a surface, and to compute rational parametrizations of its ration
al components, is outlined. (C) 1997 Academic Press Limited.