Sphere.h

#pragma once
#include "Hittable.h"

class Sphere : public Hittable {
public:
	Sphere(const Point3& center, double radius, std::shared_ptr<Material> mat)
	: center(center), radius(std::fmax(0,radius)), mat(mat)
	{}

	bool hit(const Ray& r, Interval ray_t, 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 the acceptable range
		auto root = (h - sqrtd) / a;
		if (!ray_t.surrounds(root)) {
			root = (h + sqrtd) / a;
			if (!ray_t.surrounds(root))
				return false;
		}
		/*
		6.4*/
		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 = mat;

		return true;
	}
private:
	Point3 center;
	double radius;
	std::shared_ptr<Material> mat;
};