ABSTRACT
Ruled surfaces, as the name implies, are curved surfaces constructed out of straight elements. The sets of straight lines within a curved surface are called the generators (or generatrices – see overleaf) of the surface. Perhaps the simplest example of such a surface is the cone. The most interesting such forms from an architectural point of view are helicoids, hyperbolic paraboloids (or just paraboloids), and elliptic hyperboloids of one sheet (or hyperboloids for short, and to be distinguished from elliptic hyperboloids of two sheets, which are composed of two parts separated in 3-D space).
