camera.h

#ifndef CAMERA_H
#define CAMERA_H
#include "utils.h"
#include "ray.h"
#include "vec3.h"

struct camera {
    camera() {}
    camera(point3 lookfrom, point3 lookat, vec3 vup, double vfov, double aspect_ratio, double aperture, double focus_dist, double _time0 = 0, double _time1 = 0) {
        auto theta = Pi*vfov/180., h = tan(theta/2);
        auto viewport_height = 2.0*h, viewport_width = aspect_ratio*viewport_height;
        w = unit_vector(lookfrom - lookat); // into camera
        u = unit_vector(cross(vup, w)); // unit right in camera plane
        v = cross(w, u); // unit up in camera plane
        origin = lookfrom;
        horizontal = focus_dist*viewport_width*u; vertical = focus_dist*viewport_height*v; // u v scaled
        lower_left_corner = origin - horizontal/2 - vertical/2 - focus_dist*w; // reference point (0,0)
        lens_radius = aperture/2;
        time0 = _time0; time1 = _time1; // shutter open/close times
    }
    point3 origin, lower_left_corner;
    vec3 horizontal, vertical, u, v, w;
    double lens_radius, time0, time1;
    ray get_ray(double s, double t) const {
        vec3 rd = lens_radius*random_in_unit_disk(), offset = u*rd.x() + v*rd.y(); 
        return ray(origin + offset, lower_left_corner + s*horizontal + t*vertical - origin - offset, random_double(time0, time1));
    }        
};

#endif