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onb.h
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onb.h
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#ifndef RAYTRACINGINONEWEEKEND_ONB_H
#define RAYTRACINGINONEWEEKEND_ONB_H
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(double a, double b, double 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&);
public:
vec3 axis[3];
};
void onb::build_from_w(const vec3& n) {
axis[2] = normalize(n);
vec3 a = (fabs(w().x()) > 0.9) ? vec3(0,1,0) : vec3(1,0,0);
axis[1] = normalize(cross(w(), a));
axis[0] = cross(w(), v());
}
#endif //RAYTRACINGINONEWEEKEND_ONB_H