Hyperboloids of one sheet, hyperbolic paraboloids, and Hilbert's famous "three skew lines"

293 Views Asked by At

One of Hilbert's many deceptively simple observations involved generators of hyperboloids of one sheet and hyperbolic paraboloids:

Three skew lines always define a one-sheeted hyperboloid, except in the case where they are all parallel to a single plane but not to each other. In this case, they determine a hyperbolic paraboloid (Hilbert and Cohn-Vossen 1999, p. 15).

This fact suggest the possibility that interesting transforms of these two surfaces into one another might be statable in terms of operations on triples of skew-lines.

Are there such transforms?

If not, is there some particular a priori reason why they can't exist?

I'm not asking this question idly, but rather as a follow-on to this question:

Suppose it can be shown that any right(left)-regular finite-state grammar implicitly generates a "hypar"" surface