Ink Bloom

Near-black ink billows silhouetted on a glowing interior, their edges fringed with interference colour. The sphere is implicit — a disc whose z is solved from the radius — and marched front-to-back in sixteen slices, each one folding two fbm fields into a value that splits in two: a body ramp that absorbs light, and a thin band astride the half-contour that emits a per-channel cosine fringe. Whatever transmittance survives lets the interior gradient bloom through.