Striction Curve
A Noncylindrical Ruled Surface always has a parameterization of the form
 | (1) |
, 
, and 
is called the striction curve of x. Furthermore, the striction curve does not depend on the choice of the base curve. The striction andDirector Curves of the Helicoid  | (2) |
 |  |  | (3) |
 | |  | (4) |
For the Hyperbolic Paraboloid
 | (5) |
| |  | (6) |
| |  | (7) |
See also Director Curve, Distribution Parameter, Noncylindrical Ruled Surface, Ruled Surface
References
Gray, A. ``Noncylindrical Ruled Surfaces'' and ``Examples of Striction Curves of Noncylindrical Ruled Surfaces.'' §17.3 and 17.4 in Modern Differential Geometry of Curves and Surfaces. Boca Raton, FL: CRC Press, pp. 345-350, 1993.
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