Metaballs
X-ray · layers
Parameters
How this effect works
Each blob is an invisible field of influence that falls off with distance — strong at the center, weak far away, computed as radius² / distance². For every pixel we sum the influence of all blobs and ask one question: is the total above the threshold? Above = liquid, below = empty. When two blobs approach, their fields overlap and the space between them crosses the threshold first — that's the neck that forms, exactly like two water drops touching. Nobody draws the merge; it falls out of the addition.
Doing that per pixel sounds expensive, so we cheat honestly: the field is computed on a canvas three times smaller and stretched up with smoothing on — goo has no sharp details, so nothing is lost. The rim layer colours the band just above the threshold brighter, tracing a live outline around the liquid; lower the stickiness and blobs reach out to each other from farther away.