Subsurface Scattering

Subsurface Scattering handles light that penetrates and moves within the area under a surface. Use it to make organic materials, like skin, look smooth and natural rather than rough and plastic-like. HDRP implements subsurface scattering using a screen-space blur technique.

Subsurface scattering also handles the light that penetrates GameObjects from behind and makes those GameObjects look transparent. For certain types of objects, the screen-space blur effect may not make a large visual difference. Therefore, HDRP implements two material types:

  • Subsurface Scattering implements both the screen-space blur effect and transmission (you can disable the latter).
  • Translucent only models transmission.

Enabling Subsurface Scattering

To enable subsurface scattering in your HDRP Asset:

  1. In the HDRP Asset’s Inspector window, go to the Material section and enable the Subsurface Scattering checkbox.
  2. When you enable the Subsurface Scattering checkbox, HDRP displays the High Quality option. You can Enable this option to increase the sample count and reduce the amount of visual noise the blur pass can cause by under sampling. Note that this is around two and a half times more resource intensive than the default quality.
  3. Go to Edit > Project Settings > HDRP Default Settings and, in the Default Frame Settings section, under the Lighting subsection, enable Subsurface Scattering and Transmission.

HDRP stores most subsurface scattering settings in a Diffusion Profile. HDRP supports up to 15 custom Diffusion Profiles in view at the same time, but you can override which Diffusion Profiles HDRP uses and thus use as many Diffusion Profiles as you want throughout your project. To do this, use the Diffusion Profile Override in the Volume system. This override lets you specify 15 custom Diffusion Profiles which HDRP can use for a Camera within the override's Volume.

For information on how to create and use a Diffusion Profile, see the Diffusion Profile documentation

Adding Subsurface Scattering to your Material

First, change the Material’s Material Type to Subsurface Scattering or Transmission, depending on the effect you want.

For the Subsurface Scattering material type, uncheck the Transmission checkbox to disable transmission.

Customizing Subsurface Scattering behavior

When you select Subsurface Scattering or Translucent from the Material Type drop-down, Unity exposes several new properties in the Material UI. For information on how to use these properties to customize the behavior of the subsurface scattering effect, see the Material Type documentation.

You can learn more about HDRP’s implementation in our Efficient Screen-Space Subsurface Scattering presentation.