Subsurface Scattering
Also called SSS, subsurface
Subsurface scattering is a rendering effect that models light entering a material, bouncing around inside it, and leaving somewhere else. It is what gives opal, jade, pearl, moonstone, and skin their soft inner glow instead of a hard plastic surface.
What it simulates
Some materials are neither fully opaque nor clear. Light goes in, scatters through the material, and comes back out spread and softened, so the glow appears to sit under the surface rather than on it.
Hold a hand over a torch and the edges go red. That is subsurface scattering, and without it in a render the same materials look like painted plastic.
Which stones need it
Not all of them. A faceted diamond is transparent, and its look comes from refraction and internal reflection rather than scattering. Turn subsurface scattering on there and you dull the stone.
It is the softer, translucent materials that depend on it. Getting this wrong is one of the clearest signs of a cheap render, because an opal without scattering just looks like coloured glass.
- Opal, for the milky body under the colour play
- Jade and chalcedony, which glow from within
- Moonstone, where the sheen comes from light scattering inside
- Pearl, which needs both scattering and a surface sheen
- Rose quartz, amber, and other translucent stones
Questions about Subsurface Scattering
Do diamonds need subsurface scattering in a render?
No. Diamonds are transparent, so their look comes from refraction and internal reflection. Subsurface scattering is for translucent materials such as opal, jade, moonstone, and pearl.
Can you render opals and pearls realistically?
Yes. Those materials are set up with subsurface scattering so the glow sits under the surface. Tell us the exact stone type when you send the file, since translucent stones vary a lot.