these halos need webgpu, which your browser can't reach.
the physics is in the repo — the crystals just need a device to refract the light.
ice halos
the crystals' prismatic refraction across the whole sky — the first medium on the site that knows which way is up
the weights blend the baked tables and are free; the shape, size and tilt re-bake them. the plate's c/a drives the basal paths; the tilt σ is the display's sharpness dial.
from the physics' own thresholds; the number beside a feature is the live phase LUT there (sr⁻¹). the CZA dies at 32.2°, the CHA is born at 58°, the sundogs fade by 61°.
the shipped mixed deck
the wind is both the drift and the lean — the ice falls at 0.3 m/s, so the deck's trails lie about a degree below horizontal
a halo is not painted on the sky — it is a hole. sunlight entering a hexagonal ice crystal is bent twice, and for two faces meeting at 60° no ray can be turned by less than about 22°: every crystal sends you light at 22° and more, none inside, and the ring is the edge of the shadow that geometry casts.
the crystals are ordered by gravity: plates fall with their faces horizontal and columns with their axes horizontal, so the display is tied to the horizon — sundogs on the sun's own altitude, the circumzenithal arc about the zenith, the circumhorizontal arc below a summer-noon sun. move the sun and the picture rearranges: the CZA dies at 32°, the sundogs walk outward, the circumhorizontal arc is born at 58°.
the phase is a monte carlo — millions of sun rays traced through randomly oriented prisms — so the halos rise out of noise as it converges, and the bake readout says how far it has come.