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:

  • In the HDRP Asset’s Inspector window, navigate to the Material section and enable the Subsurface Scattering checkbox.
  • When you enable the Subsurface Scattering checkbox, HDRP displays the High Quality option. You can Enable the checkbox to increase the sample count and reduce the amount of visual noise the blur pass can cause by undersampling. Note that this is around two and a half times more resource intensive than the default quality.
  • Within the HDRP Asset, locate the Default Frame Settings. Under the Lighting section, enable Subsurface Scattering and Transmission.

HDRP stores most subsurface scattering settings in a Diffusion Profile Settings Asset. The Diffusion Profile List Asset contains a set of 15 Diffusion Profiles you can edit and later assign to your Materials.

To create a Diffusion Profile Asset, navigate to Assets > Create > Rendering > Diffusion Profile Settings. To use it, open your HDRP Asset and assign the new Diffusion Profile Asset to the Diffusion Profile List property.

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.