The Scattering Tab refers to Reflection / Refraction properties. It includes some of the features present in  "mib_glossy_reflection" and "mib_glossy_refraction", as well as several additions.

The Scattered rays can either be Specular, Isotropic, Anisotropic, or Angular Dependent. Specular scattering will only allow "mirror-like" reflected and refracted rays.  

For isotropic scattering, a single Shiny parameter defines glossiness. Low values will here  increase the glossy spread.  Anisotropic scattering gives separate shiny values on the U and V axis (see Anisotropy ).  

Angular dependent scattering gives different shiny values depending on the viewing incidence.  Surfaces facing the viewer will thus have a Base_Shiny value, whereas grazing angles will have an Edge_Shiny value. The Edge_falloff determines the falloff rate towards the edge. This property allows for example to create blurred reflections which become specular at grazing angles.

 The Reflection settings allow to choose a Reflection Color, as well as the number of glossy reflected rays with the Reflection Samples parameter.  In addition,  Reflection Exposure  (0 by default) modifies the reflection weight depending on the reflected ray luminance. This allows to "filter" the reflections depending on their intensity. An Optimization parameter may enable Environment Only reflections.

  Contrarily to Mental Ray dgs_material, user don't have to worry about the physical accuracy (D+G+S=1 in dgs_material).

In T2S_Illumination, reflection has priority over the diffuse component.  So a maximum "white" reflection (without Fresnel Mask) will make the diffuse color vanish completely. A Reflection color of  0.3 0.3 0.3  will divide the diffuse color by 3, etc..... in order to keep physical consistency.

Transparency

 T2S_Illumination gives realistic  transparency,  depending on the object's thickness. Transparent objects absorb a certain amount of light depending on its wavelength. This means that certain wavelengths are absorbed and some other are not, which gives the transparency "tint".

The Refraction Color corresponds in this shader to the remaining color after an "infinite thickness". The light absorbtion follows an exponential decay, where  the  "mean life time" is controlled here by an Attenuation Distance.  The refractive Glossy samples can be set separately than reflections with Refraction Samples

 

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