This is our first post on a classic CG topic : splines. This post deals with the origin of the concept. We intend to show that some methods used today in computer modeling and design have roots in the 17th and 18th century. Splines were used for centuries A spline is a smooth curve defined by its control points. Nowadays, It is widely used in computer graphics. Historically, splines were first used in shipbuilding industries, as early as in the 1700s. Ship-designers used a device to model the splines, it’s called the spline-ducks or the spline-weights.
The spline-ducks is a flexible ruler made of thin wood or metal slat. Wood’s natural elasticity allows the strips to be flexible so they naturally provide an interpolation between the control points. Those control points are marked by weights called ducks (see the picture below). Computer aided design, Citroën and Renault Splines as we know them today were invented in the 1950s by two Frenchmen : A highly gifted mathematician working at Citroën and an engineer working at Renault. Both independently invented the same concepts. French automakers Citroën and Renault were the first to use computer aided design in the late 1950s.
Citroën introduced many innovations in the design and the prototyping of models. Paul de Casteljau, a French mathematician, while working at Citroën, developed an algorithm for evaluating calculations on a certain family of curves. The results obtained were not published for about 15 years. Pierre Bézier, Renault’s Head of Design independently invented Bézier polynomials for evaluating curves and used the results in CAD.