Blender Eevee Subsurface Scattering Profile Guide

Subsurface scattering (SSS) in Blender Eevee simulates how light penetrates translucent surfaces, scatters internally, and exits at different points. The subsurface scattering profile settings control the mathematical falloff, depth, and color distribution of this internal light dispersion, allowing artists to create realistic materials such as skin, wax, marble, and milk without the computational cost of full volumetric rendering.

What the Subsurface Scattering Profile Controls

The subsurface scattering profile determines how light spreads beneath an object's surface once it enters. Instead of reflecting immediately like an opaque surface, translucent materials absorb and disperse light over a specific distance.

Adjusting the SSS profile affects several key behaviors:

  • Scattering Falloff: The profile defines the shape of the decay curve that dictates how quickly scattered light loses intensity as it travels away from the entry point. A sharp falloff creates a harder, denser appearance (like jade), while a gradual falloff produces a soft, diffuse glow (like candle wax).
  • Wavelength-Dependent Penetration (RGB Radius): The profile allows different color wavelengths to penetrate at different depths. For realistic human skin, the red channel is typically set to scatter further than green and blue, simulating light passing through blood vessels and tissue.
  • Scattering Method: Blender offers scattering distribution models (such as Christensen-Burley and Random Walk). The profile determines which algorithm computes the light falloff, balancing physical accuracy with screen-space rendering speed.

Key Profile Parameters in the Shader

When adjusting subsurface scattering on shaders like the Principled BSDF in Eevee, the profile is shaped through specific controls:

  • Subsurface Weight: Sets the blend ratio between standard diffuse surface reflection and subsurface scattering.
  • Subsurface Radius: Represents the scattering distance vector for the Red, Green, and Blue color channels independently. This acts as the color profile for how deep each color scatters.
  • Subsurface Scale: A global multiplier for the radius values. Increasing the scale makes the entire object appear more translucent, while lowering it makes the material appear denser.
  • IOR (Index of Refraction): Adjusts the refraction angle of light rays entering the surface, changing how light enters the subsurface layer.
  • Anisotropy: Directs whether light scatters forward through the volume or backward toward the light source.

Eevee-Specific Considerations

In Blender Eevee, SSS is calculated using screen-space approximations rather than full path tracing. To ensure the SSS profile renders correctly:

  1. Subsurface Translucency: Enable translucent evaluation in the material settings so light passes through thin geometry.
  2. Screen Space Refraction & SSS: Ensure Subsurface Scattering is enabled in Eevee's render properties to compute the screen-space blur accurately.
  3. Scale Accuracy: Because the scattering profile relies on real-world units (meters/millimeters), your 3D model must have an applied object scale (Ctrl + A > Apply Scale) to prevent scattering too broadly or remaining too dense.