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junghoonjoe
05-09-2008, 05:38 PM
I came across a chart of the Index of Refraction for many materials. There was a great simple simulator on that site.

http://www.ps.missouri.edu/rickspage/refract/refraction.html

When using the mia material for Mental Ray, I checked the "use fresnel reflection" in the BRDF setting, and set the Index of Refraction to .47 - which is the IOR for gold according to this chart. I got a giant black spot on my shader when I rendered. I probably have something wrong here.

I guess I'm having trouble relating the IOR to objects that are not transparent or translucent. In this case would I keep the BRDF function on?

I'm also looking for a table that gives rough estimates for the BRDF of various materials. Thanks for your help.
KarelVR
05-09-2008, 07:01 PM
Yea, those values for non dielectric materials don't work, so those values for gold and silver are useless.
Why ?
To quote Zap:

Metals are indeed not refractive, and are indeed not dielectrics (meaning, electrical insulators). They are Conductors, and for some baroque reason these are also considered to have an "Index of Refraction".


But to get you started on decent gold with the mia material, check this page on Zap's blog:
http://mentalraytips.blogspot.com/2007/10/making-better-metal-with-miamaterial.html

Cheers,

Karel
ienrdna
05-09-2008, 07:03 PM
you are not doing enything wrong, mia material does seem to have issues with values below 1. In vray it work fine.
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