Warning: A non-numeric value encountered in /homepages/31/d121558763/htdocs/InspireGames/wp-content/themes/Divi/functions.php on line 5560

Warning: count(): Parameter must be an array or an object that implements Countable in /homepages/31/d121558763/htdocs/InspireGames/wp-includes/post-template.php on line 265

Warning: count(): Parameter must be an array or an object that implements Countable in /homepages/31/d121558763/htdocs/InspireGames/wp-includes/post-template.php on line 265

Warning: count(): Parameter must be an array or an object that implements Countable in /homepages/31/d121558763/htdocs/InspireGames/wp-includes/post-template.php on line 265

Warning: count(): Parameter must be an array or an object that implements Countable in /homepages/31/d121558763/htdocs/InspireGames/wp-includes/post-template.php on line 265

General Guidelines

To preserve realism

Incoming light energy < Outgoing Light energy

I think this means that realistically:  albedo + reflection < 1

Maths

A pretty good realtime approximation for Fresnel is the Schlick Fresnel. From the GPU Gems 3 chapter on skin:

float base = 1 – dot(V,H);
float exponential = pow( base, 5.0);
float fresnel = exponential + F0 * (1.0 – exponential);
specVal *= fresnel;

Links

https://www.fxguide.com/featured/game-environments-parta-remember-me-rendering/

Fresnel  IOR

Reflections

Refractions

The refractive index determines how much light is bent, or refracted, when entering a material.

http://wiki.brianmeanley.com/wiki/Ior.py

http://refractiveindex.info/

pbr in vray shader

http://www.shlyaev.com/rnd/37-cpp-category/54-ggx