last light

You stand at the end of the pier, facing the point on the horizon where the sun sets today. The sun and stars take their real positions over Los Angeles for this minute, the moon a close approximation, and the sky is lit by single scattering through a modeled atmosphere, so the colors of twilight come out of the arithmetic rather than a palette. Wind speed, wind direction, cloud cover and humidity come from a live forecast and shape the waves, the clouds and the haze.

The sea is a sum of travelling waves: a long westerly swell and a wind sea sized by the Pierson–Moskowitz spectrum. Roughness too fine to draw follows Cox and Munk's measurements of sunlit sea slopes, and each grain either catches the sun or doesn't, with a probability that matches the expected glare. That is where the path of light comes from.

Every grain lives about a second. It is born in place, swells, and is carried through a field of slow vortices before it fades and forms again at home. The vortices are the curl of a noise field, so the picture swirls without tearing, and the horizon is one of their streamlines, so sky and sea never mix. Wind opens more of the field and quickens it. The motion is borrowed from cullenwebber/three-ml-sharp. Built with vgpu on WebGPU.