sub_sky

Studio cove dome surface shader for the substance part, drawn on the inside of a large inverted sphere. A dark charcoal-blue infinity cove lit by an overhead softbox ring and four low rim slits (two warm, two cool), dithered sub-1/255 so the dark gradients survive the tonemap without banding.

studio_env() is the shared studio environment function — sub_sphere, sub_floor and sub_chrome carry an identical copy so every reflection in the part matches this dome exactly. The softbox ring in the environment sits at the same elevation as the part's physical emissive ring geometry, so the brightest reflection reads as coming from the visible fixture.