#404Soap Bubble Iridescence

A glossy soap-bubble orb hovering in a dark studio. A fake sphere normal drives both a matcap-style environment reflection — a soft gradient surround with two studio softboxes — and physical thin-film interference: the optical path (2·n·thickness·cosθ) sets a phase per wavelength that is integrated across the spectrum through an inline wavelength→RGB response, so the rainbow comes from real interference rather than a palette. Curl-marbled thickness and a gravity gradient pool the colour toward the base and crowd the orders into the grazing rim, where Fresnel brightening and a sharp catch-light finish the glass. Move to steer the light, scroll to grow the film, press to swell the bubble.