Subsurface scattering (SSS, subsurface scattering)

Subsurface scattering, SSS (also known as 3 S), is translated as subsurface scattering. In the real world, many objects are a little translucent, such as skin, Jade, wax, marble, milk, etc. These translucent materials are transmitted by several light sources, and the object itself will be affected by the thickness of the material to display different light transmittance. The light in these transmission parts can also be mixed and interfere with each other. To put it simply, the light emits light on the surface, scattering it in the material, and then emits the surface from a place different from the injection point.
SSS softens the overall lighting effect. The light in one area will penetrate into the surrounding area of the surface, and the small surface details will become invisible. The deeper the light goes into the object, the more serious the attenuation and scattering will be. Let's take the skin as an example. In the link between the illuminating area and the shadow area, scattering often leads to a slight red color offset. This is because the light illuminates the skin and enters the skin, it is then dispersed and absorbed by subcutaneous vessels and tissues, and then left from the shadow part. The scattering effect is more obvious in the thin area of the skin, such as the nostrils and the surroundings of the ears. As shown in:

Below are some pictures of SSS effects:


Zhou xingchi's latest lunar New Year Movie "Yangtze River 7" contains the "seven" skin is made of SSS material effect:


Note: All images are from the Internet. Thanks to the author!