drop_rings

The rings a falling drop leaves on a liquid surface. A ring is a travelling wave rather than a painted circle, so the shader builds a height field of concentric wave packets — each one starting where the drop landed, running outward at a fixed speed and losing height as it spreads — takes the field's radial slope, and reads the scene colour under the surface through it. The crest catches the lamp; the trough does not.

The drips are periodic: lane 0 carries the period and phase, so the same rings cross the same surface every time the film is played.

speed, width, crests and decay are the wave; refract how far its slope bends what is under it; crestLight and crestColor the highlight; coverage the whole card's weight.

Lane 0 (shader_data[0]) carries (film seconds, strength 0..1, drip period, phase), written every film frame by demo/stages/air.module.