Subsurface Scattering
Light entering and bouncing inside a material
Also known as: SSS · Subsurface
Definition
Subsurface scattering (SSS) simulates how light enters a translucent material — skin, wax, marble, leaves, milk — bounces around inside, and re-emerges at a slightly different point. It is what makes a hand backlit by sunlight glow reddish at the fingertips, or marble appear to have depth instead of just being a coloured surface. Real-time SSS is expensive but essential for believable skin shading in characters.
In production
UE5 ships a Subsurface Profile shading model with separate radius and tint controls per character, letting artists set distinct scattering behaviour for skin versus, say, a translucent ear where light passes through more directly. For mobile/lower-end targets, a cheap approximation is fake SSS via a wrapped-lambert term added to Emissive, avoiding the cost of the full screen-space diffusion pass higher-end platforms use. Unity's HDRP implements a similar Diffusion Profile asset, with a "Transmission Mask" that lets thin geometry like ears or leaves transmit light from behind. A common mistake is applying the same SSS profile to every character regardless of skin tone or thickness — the scattering radius should scale with material density, since a default profile will look waxy on thin surfaces like eyelids without tuning.
Learn Subsurface Scattering in
Tools that use Subsurface Scattering
See also
PBR
Physically Based Rendering
Shader Graph
Visual shader authoring
Fresnel
Edge-on reflection increase
Thickness Map
How thick the object is at every point
Two Sided Material
Show a surface from both sides
Skin Shading
Subsurface scattering and specular for skin
Character Skin Looks Plastic
Skin that reads as rubber or wax