T2S_illumination – x64 version released!
Fresnel mask
The Fresnel Laws describe the behaviour of light at the interface between two different media. A part of the incoming light is reflected, while another part is trasmitted (i.e. refracted or absorbed). The proportion of reflected light only depends on on the (complex) refractive index and on the angle of incidence.
For more details concerning the Fresnel equations, please refer to http://www.odforce.net/wiki/index.php/ReflectanceFunctions#The_Fresnel_Effect
In the T2S_Illumination shader the Fresnel Mask can be evaluated by one of the following Modes :
- Physical
- Custom
- Preset
- T2S File
Physical
Physical Mode will evaluate the Fresnel equations to determine the Reflection coefficient R and the Transimission coefficient T = 1 – R..
and
where n1 and n2 are the “In” and “Out” complex refractive index, (IOR and MediaIn in the shader)
qi is the incident angle and qt the transmitted angle deduced by the Snell Law ( n1 sin(qi) = n2 sin(qt) )
Rs and Rp correspond therefore to the fraction of s-polarized and p-polarized light which is reflected (here an average of these two waves is used)
If the refractive index are complex, an absorbtion coefficient k , which determines how fast the light is absorbed, needs to be determined.
The Schlick approximation can also be chosen for fast calculations.
Custom
Custom mode allows to set manually the Base Weight for facing angles and Edge Weight for grazing angles. An Edge Falloff parameter is used to control the Fresnel Falloff (this mode is similar to what is included in mib_glossy_reflections)
Preset
Preset Mode will allow to choose among a list of predetermined Materials, which contain the Refractive Index for Red, Green and Blue light. A Physical “Complex Fresnel” Calculation is then performed. This procedure tints the reflections depending on the Fresnel Reflectivity.
T2S File
T2S Files can be used to input user-defined complex Fresnel parameters (IOR and Absorbtion Coef) for R, G and B. For more details concerning the T2S File Format, please click here.
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The first image has been rendered with a simple Lambert with a Reflectivity of 0.5.
The second image has been rendered with the T2S_FresnelMask plugged into the reflectivity port of the Lambert node, using a refractive index of 5 with Schlick’s approximation. It can be seen how the grazing angles become much more reflective, adding realism to the scene.
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Hi. I am using XSI 7.01 and have installed the addons T2S Illumination, and T2S Materials.
I’m unable to load any of them.
When I go to Get>Materials the menu shows up but doesn’t have anything in there.
Do you have any advice? or an install tutorial.
Thanks.
Hey Chris! Im using the same version and had the same problem but I got it woring! Make sure that you download that Microsoft visual C++ file (there are links on this site depending on what version of T2S your using. Then instead of using the get-material just load it as a material preset from the shadertree. You do this by opening the material PPG and at your right top corner there is a map icon. Load and save preset…) Thats how i got it working!
T2S_Illumination_1.1_x86-x64.xsiaddon instal but not visible in render tree options in xsi later 7.01 your older version is work! and the main, shader not work with property of inclusive or exclusive light!!! it work with all light in scene – its not good!!!
Hi, first thanks for such a great shader, we’ve made great use of it.
We now have a need to exactly replicate the look of the original 32 bit shaders for 5.11 in Soft 2010 64 bit. In the new version there are some extra options in the Output Tab regarding how Diffuse and BDRF elements are mixed. I am trying to replicate the way that the original shader mixed these elements. I can isolate the Diffuse and the Reflection elements in the new shader and they look exactly the same as the isolated versions in the original shader. Getting these ‘layers’ to mix in the same way as the original is proving difficult though.
I assume there was a hardcoded setup in the original shader, but none of the new options seem to match it. Do you have any idea how I might achieve the look of teh original?
Many thanks,
Adam.