A question about reflectivity

[Roodogg]

Hi guys.

 

First, thanks in advance for reading this 'essay'.

 

I have a question about the reflectivity of different materials, specifically with V-Ray but I think the principal is correct for other rendering engines. I am not particularly concerned with the glossiness or anisotropy at this point (unless you feel it is significant).

 

I understand that in the real world, Steel reflects around 60% of the light that hits it and white emulsion or white paper reflects around 75% of the light that hits it.

 

Obviously when creating CGI materials, we use a diffuse colour to simulate a large portion of the reflected light on matte materials. for example for white emulsion (Real world - reflective amount is around 75%), I would use RGB 190,190,190 and have a very low fresnel reflection for highlights.

 

When creating a mirror, the diffuse colour is almost insignificant as the reflective value is near or at 100% and I probably wouldn't bother using Fresnel falloff.

 

My question is on translating materials in the middle ground two such as metals, plastic or wood to CGI using real world reflectivity charts such as below (assuming they are accurate).

 

http://www.gfxelite.de/forum/3d_animation/8205-index_refraction_table_reflections.html

 

I am looking for a procedural way in order to produce physically accurate materials using correct reflective percentages?

 

Any advice or reference to books / tutorials would be a massive help. Thanks for reading!

[John Dollus]

those values for non-transparent materials are assuming an ideal diffuse condition usually reserved for lighting calculation software. For photorealistic solid materials, you should be more concerned with the brdf function using a falloff map and custom curves.

Vray docs/tuts are more concerned with how something looks visually as opposed to technical accuracy so you might want to look into a few of the mental ray docs to help with the explanation -

http://mentalraytips.blogspot.com/2007/10/making-better-metal-with-miamaterial.html

http://docs.autodesk.com/3DSMAX/15/ENU/3ds-Max-Help/index.html?url=files/GUID-8A661F93-AC62-4733-A675-1A4324DA026B.htm,topicNumber=d30e365149