A geometric modelling system based on rational Gaussian (RaG) curves a
nd surfaces is introduced. The generation of simple geometric primitiv
es such as lines, circles, and ellipses with RaG curves, and the gener
ation of planes, spheres, ellipsoids, cylinders, cones, and tori with
RaG surfaces are discussed. The design of freeform closed, half-closed
, and open shapes using RaG surfaces is also considered. The control p
oints of a RaG surface are not required to form a topologically rectan
gular grid, but, rather, they can form an arbitrary grid.