www.si-community.com

I recently read this article about custom fresnel curves for more realistic shading:

http://therenderblog.com/custom-fresnel-curves-in-maya/

and the same idea is on this tutorial for shading metals in modo:

https://vimeo.com/ondemand/shading1

wondering if its possible to create such curves in XSI, regardless of renderer (MR, vray or Arnold)...

Should be incidence node, plugged into scalar math curve. That's approximate translation of Maya sampler info and remap value.
Another story is, *what* you will remap with this. Is it a plain mix of diffuse and reflection shading, or there is a sort of dumping on top of everything, like energy conservation. Or there's something else in mix, too...
Anyway, it's interesting that in entire article ( if I'm correct), no word about RGB Fresnel, it seems he just considers as 'enough correct' to have a monochrome blend. Put numbers into equitation, and you're there.... For small comparison, about ten years old custom Mental Ray shader called T2S Illumination, had a bunch of presets for various materials, I'd believe measured, all of them played in all RGB channels, giving a much better (imho) description of things like gold or copper - instead of just one of many Fresnel approximations.
By the way, default diffuse - reflection mix of MIA Mental Ray material, I think it is, in SI render tree 'language': inverted incidence, plugged into scalar math exponent node (with exponent of five), change range from 0.2 to 1.

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Thanks Mathaeus for your reply and time!
you are much more ahead of xsi knowlegde than me, maybe some stelar years

the results seens pretty convincing (on the images show in the video demo)



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Related subject on NVidia ARC forum if you are interested.

https://forum.nvidia-arc.com/showthread ... IOR-Curves

Refractive Index database

http://refractiveindex.info/

I also attached the last zip file from JJJenkins if your are not a NVidia ARC Forum member. It's for Maya but you probably can de-construct it for Softimage

A more recent version of the script is available on CreativeCrash at:

http://www.creativecrash.com/maya/scrip ... renderblog

P.S. The RGB values are explained in part 2 of the article.

http://therenderblog.com/custom-fresnel ... ya-part-2/