sphere.h

#ifndef SPHERE_H
#define SPHERE_H



#include "hittable.h"
#include "vec3.h"


class sphere : public hittable {
public:
	sphere(const point3& center, double radius) : center(center), radius(std::fmax(0, radius)) {}

	bool hit(const ray& r, double ray_tmin, double ray_tmax, hit_record& rec) const override {
		vec3 oc = center - r.origin();
		auto a = r.direction().length_squared();
		auto h = dot(r.direction(), oc);
		auto c = oc.length_squared() - radius * radius;

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

		auto sqrtd = std::sqrt(discriminant);

		// Find the nearest root that lies in acceptable range
		auto root = (h - sqrtd) / a;

		if (root <= ray_tmin || ray_tmax <= root) {
			root = (h + sqrtd) / a;
			if (root <= ray_tmin || ray_tmax <= 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);


		return true;
	}


private:
	point3 center;
	double radius;
};

#endif