metal.hpp

#pragma once

#include "material.hpp"
#include "vec3.hpp"

bool refract(const vec3& v, const vec3& n, double ni_over_nt, vec3& refracted)
{
    vec3 uv = unit_vector(v);
    double dt = dot(uv, n);
    double discriminant = 1.0 - ni_over_nt * ni_over_nt * (1 - dt*dt);
    if (discriminant > 0) {
        refracted = ni_over_nt*(uv - n * dt) - n * sqrt(discriminant);
        return true;
    }
    else {
        return false;
    }
}

vec3 reflect(const vec3& v, const vec3& n)
{
	return v - 2 * dot(v, n)*n;
}

class metal : public material
{
public:
    explicit metal(const vec3& a, double f = 0.1) : albedo(a), fuzz( f < 1 ? f : 1) {}

    bool scatter(const ray& r_in, const hit_record& rec, vec3& attenuation, ray& scattered) const override
    {
        vec3 reflected = reflect(unit_vector(r_in.direction()), rec.normal);
        scattered = ray{rec.p, reflected + fuzz * random_in_unit_sphere()};
        attenuation = albedo;
        return dot(scattered.direction(), rec.normal) > 0;
    }

    vec3 albedo;
    double fuzz;
};