lerp
Linear interpolation between two values: `lerp(a, b, t) = (1 − t) · a + t · b`. At `t = 0` you get `a`, at `t = 1` you get `b`, in between you trace a straight line. Works on numbers, points, colors, transformations — anything that supports addition and scaling. The single primitive on which Bezier curves, animation tweening, gradient shading, and most computer-graphics interpolation are built.
1962 · Pierre Bézier (Renault) & Paul de Casteljau (Citroën), independently · Paris
Bézier and de Casteljau, working at rival French car companies, both invented the same recursive linear-interpolation construction to design car body curves on early CAD systems. De Casteljau's work was kept as a trade secret; Bézier published. The curves bear Bézier's name; the algorithm bears de Casteljau's.