This tab defines the parameters for Subsurface scattering (SSS).
Dali Renderer uses full stochastic SSS Monte Carlo calculation. Every material using SSS must be bounded by a closed surface. All texture maps are sampled only on this surface and further calculations inside the material use these values. This is different from Dali Volumetric, which samples the data internally as well.
SSS is a simplified and fast version of the algorithm.
However, surfaces with SSS can be nested. Internal materials with SSS will replace external ones, their parameters will not be combined.
If the SSS is emissive, then it will not be converted to an emitter. This can result in more noise than with the Dali Volumetric.
The basic principle of light propagation in a material:
It is assumed that the material consists of a large number of small particles. A beam of light flies between particles until it collides with one of them. This distance on average determines the depth of penetration of the beam into the material. After a collision, the light can be absorbed by the particle (absorption), or it can be re-emitted in a new direction (scattering). In addition, a particle can emit its own light (emission). If a beam of light (many photons) goes through the material, then some of them will fly through, and some will not. For a beam of light that has passed through, this will be a change in its hue. Therefore, it is appropriate to speak of absorption in terms of hue and the distance at which that hue will be obtained from initially white light.
Enable
Enables this component. Without this option, any ray that goes inside the material will remain straight.
Apply to any transmission
Without this option, SSS will only work with the diffuse Translucence component only. The option enables SSS for Dielectric Transmission also.
Expert Mode
Allows you to switch the interface from basic to expert mode and vice versa.
Scattering Albedo (Base mode only)
Only in basic mode. Determines how much of the total fading is the scattering component.
Adjustable by base weight, color, spectral spline and texture map. The texture map is only defined on the bounding surface for SSS. The "At distance" value determines the average penetration depth of the beam into the material before it hits the particle.
Absorption (Base mode)
For basic mode: determines what color should be obtained from the initially white beam at a given distance (At distance).
Adjustable by base weight, color, spectral spline and texture map. The texture map is only defined on the bounding surface for SSS. The distance value is set in the current distance units in the scene.
Absorption (Expert mode)
For expert mode: sets the sigma value for absorption.
Scattering (Expert mode only)
For expert mode: sets the sigma value for scattering.
Anisotropy
Non-uniformity of light scattering on a particle. It varies from -1 to 1. Negative values scatter mostly backwards, positive ones scatter forwards. A value of zero gives symmetric spherical scattering. Adjustable by base weight, color, spectral spline and texture map. The texture map is only defined on the bounding surface for SSS.
Emission
Specifies the emission of the particle. Adjustable by base weight, color, spectral spline and texture map. The texture map is only defined on the bounding surface for SSS.
Kelvin
Emission temperature in Kelvin. Adjustable by base weight and texture map. The texture map is only defined on the bounding surface for SSS.
