# What determines how much light is reflected and refracted?

I'm currently working on a physics-based puzzle game with light refraction. I've read about the reflection/refraction incidence ratio, and how it's the proportion of the sine values of the angle of incidences.

However, what formula, if there are any, determines the threshold for % of light reflected and % of light refracted?

is the % of light reflected/refracted always either 0% or 100% (that is, they're always either reflected or refracted)? Or is there a curve of some sort for this?

• This is an exact duplicate of physics.stackexchange.com/questions/339/… . – nibot Mar 12 '11 at 23:01
• This is a very important question in 3D computer graphics, especially in ray tracing. Unlike physicists, the CG artists and makers of their software need to calculate such things very fast, and make a wide variety of materials look real (or unreal). – DarenW Mar 13 '11 at 3:42

## 2 Answers

Look here:

http://en.wikipedia.org/wiki/Fresnel_equations

This is for transparent media, the formulas for metals are somewhat more complicated.

There is most definitely an actual literal curve of light reflection. There is such a thing called the "critical angle" in which, at that certain point, is entirely REFLECTED at 100%. However, any angle past that point creates a refraction and will dissipate the power of your reflection. Meaning if you shine a light at a mirror at the critical angle, it will travel at 100% lumosity. But each angle you move afterwards will gradually sink the lights power as it bounces, and more passes it through at the refraction angle. But do not forget your heat index as it reflects. Another thing you have to take into consideration, is your reflection/refraction material and most forgotten, the air in between the objects it's travels through.