The Fresnel T2S files are used to get colored Fresnel Masks. It allows to set an independent refractive index (ior) and absorbtion coefficient (k) for R,G and B, and creates fluctuations on the reflection colors (current version of T2S_Illumination only uses colored IOR for reflections).

Thus, the Fresnel Mask can be white for grazing angles, and become colored depending on the incidence.

Here is an example of a Fresnel T2S file

;   Gold Fresnel Preset
;
;
; IOR values adapted from SOPRA NK-Database measures
;

[Model]
Type=Fresnel

[FresnelParameters]

R_ior = 0.16
R_k   = 4.0

G_ior = 0.4
G_k   = 2.65

B_ior = 1.61
B_k   = 1.94

 The values obtained for IOR presets have already been included in the Fresnel Presets of T2S_Illumination. Some of them are included in the t2s_filepack01 in order to bring examples for those wanting to create their own Fresnel t2s files.