Written using CGI 5 October 1987 by Ron Record ([email protected]) Rewritten using X11 20 Apr 1993 by Ron Record ([email protected])

This program uses bouncing balls as control points for generating cubic curves. Two methods are used to calculate the curve. One, the Bezier form for defining a cubic, uses n control points with the tangent vectors at the endpoints being defined by the line segments between control points. The other, referred to as the B-spline cubic representation, doesn't pass thru any control points. In the B-spline, the points where the curve "joins" and their derivatives are weighted sums of the three immediately adjacent control points.

From "Fundamentals of Interactive Computer Graphics" by Foley and Van Dam : "This terminology traces back to the long flexible strips of metal, called splines, used by draftsmen to lay out the surfaces of airplanes and ships. The metal splines, unless severely stressed, also have second-order continuity."

From "Principles of Interactive Computer Graphics" by Newman and Sproull : "P. Bezier, of the French firm Regie Renault, pioneered the use of computer modeling of surfaces in automobile design. His UNISURF system, used by designers since 1972, has been applied to define the outer panels of several cars marketed by Renault."