Schlick’s Approximation


$$R_0 = (\frac{n_1 - n_2}{n_1 + n_2})^2$$
$$R = R_0 + (1 - R_0)(1 - \cos{\theta_j})^2$$
actual is [Fresnel Equation](https://texonom.com/fresnel-equation-262e2282f8f54687a7beda847452f006) 









