Macro raytracer::refract

macro_rules! refract {
    ($v:expr, $normal:expr, $n:expr) => { ... };
}

Alternative for Vec3::refract.

Examples

// Glass surface
let n = 1.5; // n1 / n2, where n1 = 1.5 (glass) and n2 = 1.0 (air)
let normal = vec3!(0.0, 1.0, 0.0);

// Rays perpendicular to the surface aren't affected by refraction
let incident = vec3!(0.0, -1.0, 0.0);
assert_eq!(refract!(incident, normal, n), Some(incident));

// Rays coming from an angle are refracted
let incident = vec3!(-0.7, -1.0, 0.0);
assert_eq!(refract!(incident, normal, n), Some(vec3!(-0.86019355, -0.5099678, 0.0)));

// At critical angles (nearing 0), rays aren't refracted, only reflected
let incident = vec3!(-1.0, -0.05, 0.0);
assert_eq!(refract!(incident, normal, n), None); // from outside of the surface

let incident = vec3!(1.0, 0.05, 0.0);
assert_eq!(refract!(incident, normal, n), None); // from inside of the surface