🌈 Raindrop Ray Fan: Descartes Rainbow, Dispersion and Alexander Dark Band

Trace sunlight through a spherical raindrop with Snell's law and Fresnel losses, find the Descartes minimum-deviation ray for each colour, and see the resulting primary and secondary bows and the dark band between them over a meadow.

3D · Three.js / WebGL renderer · 60 FPS target · runs fully client-side, no install