sphere.cpp

#include "sphere.h"

bool sphere::hit(const Ray& r, double t_min, double t_max, hit_record& rec) const{
    Vec3 oc = r.origin() - center;
    auto a = r.direction().length_squared();
    auto half_b = dot(oc, r.direction());
    auto c = oc.length_squared() - radius*radius;

    auto discriminant = half_b*half_b - a * c;
    if(discriminant < 0){
        return false;
    }
    auto sqrtd = sqrt(discriminant);

    auto root = (-half_b - sqrtd) / a;
    if(root < t_min || t_max < root){
        root = (-half_b + sqrtd) / a;
        if(root < t_min || t_max < root){
            return false;
        }
    }
    rec.t = root;
    rec.p = r.at(rec.t);
    Vec3 outward_normal = (rec.p - center) / radius;
    rec.set_face_normal(r, outward_normal);
    rec.mat_ptr = mat_ptr;

    return true;
}