The Dali Physical physical material consists of two layers: the Coating layer and the main RTCD core. The main core is divided into 4 components Reflection, Refraction (Transmission), Conductor and Diffuse. Additionally, the emissive component and special settings for transparency and displacement are included.
Depending on the side of the surface from which the beam comes, it hits the Coating layer or the RTCD core. If the weight of the Coating layer is not equal to 1.0, then the beam with a probability (1-Weight of the Coating Layer) will pass directly to the RTCD core.
When the beam passes through the Coating layer, one of two models is used:
- simplified, in which there are no multiple reflections of the beam from the boundaries of the layers;
- accurate, where the beam can be reflected hundreds of times until it fades or goes out.
The following rules apply when using core RTCD options:
The RTCD core has weight. If it is not equal to 1.0, then the rest of the energy goes to the diffuse component.
The energy entering the RTCD is distributed between the dielectric and the metal. The energy that goes to the metal component is not involved anywhere else. It reflects off the metal. The rest of the energy goes into the dielectric.
First, the Fresnel coefficient for the dielectric component is calculated. The calculated amount of energy is spent on reflection from the dielectric, the rest goes as Transmission - refraction in the dielectric. If the Transmission weight is less than 1.0, then the rest of the energy goes into the diffuse component.
Thus, the diffuse component can receive energy in two ways - directly, bypassing the RTCD; and as the part that did not go to Transmission.
If the beam went inside the material and if the SSS parameters are set, then a special rendering stage begins - the calculation of subsurface scattering, taking into account the priorities of nested dielectrics.
