Effect

Liquid glass caustics

Bright, wavy, focused light lines and cells — the network of light at the bottom of a pool or cast by a glass on a table.

Also called water light, pool light, light network, voronoi light, caustic

A frosted rounded pane over an animated caustic light network on deep teal.
A frosted rounded pane over an animated caustic light network on deep teal. (dark)

Where to use it

Use in
Backgrounds and hero scenes (water, wellness, weather, AI ambience), light cast by a large glass object onto the surface below. Use sparingly and dimly behind chrome.
Avoid
Bright caustics directly behind text-bearing glass (kills legibility); fast animation; caustics as a UI fill.

Parameters

cell scale 3–7 cells per 300 px, intensity 20–40 % additive, two layers at different scales/speeds, animation 0.2–0.6 units/s.

How it is built

Design tool
Use a caustic texture (photo or generated Voronoi-edge pattern) in Screen/Add at 20–40 %, slightly blurred, tinted to the light colour.
Web
WebGL/canvas background (see caustics() in the web recipe); CSS fallback: a looping caustic texture video or image with mix-blend-mode: screen.
Shader, in one line
Worley cell borders: pow(1 - smoothstep(0, 0.3, F2 - F1), 3), multiply two animated layers, add to the backdrop.