Sphere.h

//
//  Sphere.h
//  ray-tracing-weekend
//
//  Created by Sun, Joy (Agoda) on 2/16/2559 BE.
//  Copyright © 2559 Sun, Joy (Agoda). All rights reserved.
//

#ifndef Sphere_h
#define Sphere_h

#include "Hitable.h"

class Sphere:public Hitable{
public:
    Sphere(){}
    Sphere(Vec3 cent, float r, Material *m):center(cent),radius(r), mat_ptr(m) {};
    
    virtual bool hit(Ray &ray, float t_min, float t_max, hit_record &rec) const;
    
    Vec3 center;
    float radius;
    Material *mat_ptr;
    
};

bool Sphere::hit(Ray &ray, float t_min, float t_max, hit_record &rec) const{
    Vec3 oc = ray.origin() - center;
    float a = ray.direction().dot(ray.direction());
    float b = oc.dot(ray.direction());
    float c = oc.dot(oc) - radius*radius;
    
    float discriminant = b*b - a*c;
    
    if (discriminant > 0) {
        float temp = (-b - sqrt(discriminant)) / a;
        if (temp < t_max && temp > t_min) {
            rec.t = temp;
            rec.p = ray.point_at_parameter(rec.t);
            rec.normal = (rec.p - center) / radius;
            rec.mat_ptr = mat_ptr;
            return true;
        }
        temp = (-b + sqrt(discriminant)) / a;
        if (temp < t_max && temp > t_min) {
            rec.t = temp;
            rec.p = ray.point_at_parameter(rec.t);
            rec.normal = (rec.p - center) / radius;
            rec.mat_ptr = mat_ptr;
            return true;
        }
        
    }
    return false;
    
}


#endif /* Sphere_h */