Smoke Orb

Smoke sealed inside a glass ball, floating in a wall-only studio void. The view ray refracts once at the shell and is then marched through sixteen slices of a warped fbm field, each one taking two cheap taps toward the key light for self-shadow and integrating Beer-Lambert transmittance. What the smoke leaves through shows the graded wall behind it, sampled once per channel at three indices of refraction. Every colour in the room is a swatch: the wall gradient, the two lamp bounces, the four glass highlights and the smoke albedo.