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No.132 · Backgrounds

Caustic Pool

Light refracted through moving water onto the floor of a dark pool — a web of filaments, split faintly into colour.

The prompt

Written for the variant you picked above: Night pool

Write a WebGL1 fragment-shader background that looks like the bottom of a pool at night: a deep, nearly black blue floor crossed by the shifting web of caustic light that moving water throws down. Build the caustics from cellular noise rather than sine soup: compute F2 − F1 (distance to the nearest cell edge) of a Worley field whose feature points drift in small circles over time. Turn each edge into a thin bright filament (1 − smoothstep(0, ~0.18), cubed). Use two such layers at different scales moving in opposite directions, add them, and add their product boosted — where the webs cross, the light pools into bright knots, just like real caustics. Bend the whole floor with a slow low-frequency swell. Sample the pattern three times with a tiny horizontal offset per channel for a faint chromatic split at the edges of every filament. Grade it like water: brighter in the shallows (top), darker and bluer toward the bottom, with a soft vignette and fine dither. The cursor is a hand in the water: a gentle Gaussian lens around the pointer that magnifies and brightens the light beneath it, easing in and out. Render at 0.65× resolution (0.45× and ~30fps on touch), pause offscreen, and draw a single frame under reduced motion. Selected variant — Night pool: Night pool: cool white-blue caustic light (tint #b9d4f0) over a near-black blue floor (depth #050a12).

Notes

Interaction
A soft magnifying lens of brighter light follows the pointer inside the pool and fades when it leaves.
Motion
Continuous shader time; feature points orbit; swell warps the floor; pointer lens eases at 6–8% per frame.
Accessibility
Canvas is aria-hidden; reduced motion renders one still frame.
Responsive
Fills its container at reduced internal resolution for performance.
On touch
No lens on touch; the light still moves.

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301 components