camera.hpp

#pragma once

#include "vec3.hpp"
#include "ray.hpp"

vec3 random_in_unit_disk()
{
	vec3 p;
	do {
		p = 2.0*vec3{drand48(), drand48(), 0} - vec3{1, 1, 0};
	} while (dot(p, p) >= 1.0);
	return p;
}

class camera
{
public:
	camera(vec3 lookfrom, vec3 lookat, vec3 vup, double vfov, double aspect, double aperture, double focus_dist)
	{
		double theta = vfov*M_PI/180;
		double half_height = tan(theta/2);
		double half_width = aspect * half_height;

		origin = lookfrom;
		w = unit_vector(lookfrom - lookat);
		u = unit_vector(cross(vup, w));
		v = cross(w, u);

		lower_left_corner = vec3{-half_width, -half_height, -1.0};
		lower_left_corner = origin - half_width*focus_dist*u - half_height*focus_dist*v - focus_dist*w;
		horizontal = 2*half_width*focus_dist*u;
		vertical = 2*half_height*focus_dist*v;
		lens_radius = aperture/2;
	}

    ray get_ray(double s, double t)
    {
		vec3 rd = lens_radius*random_in_unit_disk();
		vec3 offset = u*rd.x() + v*rd.y();
        return ray(origin+offset, lower_left_corner + s*horizontal + t*vertical - origin - offset);
    }

    vec3 origin;
    vec3 lower_left_corner;
    vec3 horizontal;
    vec3 vertical;

	vec3 w;
	vec3 u;
	vec3 v;
	double lens_radius;
};