Rendering technique simulating light that enters a material, scatters inside and exits elsewhere — the key to believable digital skin, wax and marble.
Subsurface Scattering (SSS) describes what light does to skin, wax, milk, or marble: it doesn't bounce off the surface but penetrates, scatters within the material, and re-emerges slightly colored and softened. Holding a hand in front of a flashlight demonstrates the effect – the red glow between the fingers. Without SSS, digital skin appears like painted plastic; this is why the technique has been a mandatory part of character rendering since the early 2000s.
How It Works
Physically accurate would be to track every light ray through the material – too expensive for production rendering. Renderers therefore approximate the effect: classically via diffusion profiles (light is distributed as a blur across the surface, weighted by penetration depth per color channel), more modernly via random walk methods that actually trace scattering paths stochastically and correctly illuminate details like thin ears or nostrils. The visible difference: Random Walk keeps edges and thin areas believable but costs more processing time.
In Production
SSS is a look development topic: the scattering color and depth per channel determines whether skin appears lifelike or waxy. A common mistake is too much scattering – the character then appears translucent like a candle. Reference photos under controlled lighting (especially backlighting on ears and fingers) are the usual comparison between a digital double and a real actor.
Related terms
Quiz
1. Was beschreibt „Streuung unter der Oberfläche" am besten?
2. Zu welchem Department gehört „Streuung unter der Oberfläche"?