onb.hpp

//
// Created by Andrew Yang on 4/9/21.
//

#ifndef RAYTRACING_ONB_HPP
#define RAYTRACING_ONB_HPP

#include "vec3.hpp"

class onb {
public:
    onb() = default;

    inline vec3 operator[](int i) const { return axis[i]; }

    vec3 u() const { return axis[0]; }
    vec3 v() const { return axis[1]; }
    vec3 w() const { return axis[2]; }

    vec3 local(float a, float b, float c) const {
        return a*u() + b*v() + c*w();
    }

    vec3 local(const vec3& a) const {
        return a.x()*u() + a.y()*v() + a.z()*w();
    }

    void build_from_w(const vec3& n);

public:
    vec3 axis[3];
};

void onb::build_from_w(const vec3& n) {
    axis[2] = unit_vector(n);
    vec3 a = (fabs(w().x()) > .9f) ? vec3(0,1,0) : vec3(1,0,0);
    axis[1] = unit_vector(cross(w(), a));
    axis[0] = cross(w(), v());
}

#endif //RAYTRACING_ONB_HPP