Thin-film interference via cosine palette — shifting petrol sheen.

Two octaves of fractal noise, one drifting forward and one backward, drive an RGB cosine palette whose channels are offset by a third of a cycle each. That phase offset is what produces iridescence: the same noise value reads as a different hue per channel, exactly as a thin film splits white light. A radial falloff darkens the frame edges so the sheen sits on a surface instead of floating. Reads as expensive without any texture assets.