Perlin noise
A smooth, natural-looking pseudo-random function invented for CGI textures — the seed of a thousand procedural worlds.
Ken Perlin created it in 1983 for the film Tron, frustrated that computer imagery looked too clean. Unlike white noise, Perlin noise is continuous and coherent: nearby points have similar values, so it reads as organic — clouds, marble, terrain, fire. It assigns random gradient vectors to a grid of points and interpolates between them with a smooth falloff.
Perlin won an Academy Award in 1997 for the technique. He later published simplex noise (2001) to fix directional artefacts and scale better to higher dimensions. Stacking several frequencies (octaves) of the noise — fractal Brownian motion — produces the rugged detail used for heightmaps and procedural landscapes.