Subsurface scattering (often shortened to SSS) describes the way light penetrates the surface of a translucent material, scatters around inside it, and exits at a different point. It's why human skin glows warmly when backlit, why a wax candle has that soft inner illumination, and why honed marble looks alive rather than dead-flat.
In architectural rendering, SSS matters most for stone (marble, alabaster, onyx), thin fabric drapery, wax candles, certain ceramics, and some plant material like leaves. Without SSS, these materials look painted-on rather than physically present. A marble countertop without SSS reads as a printed photograph of marble glued to the surface; with SSS it reads as a real slab of stone.
AI rendering handles SSS implicitly — the model has learned what translucent materials look like — but it's worth specifying in the prompt when you want it. Phrases like 'honed marble with subtle subsurface glow' or 'thin linen drapery with light passing through' push the AI toward the SSS-aware output. Without that nudge, the AI may render the material as opaque, especially for less common translucent surfaces like alabaster.
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