toytracer/camera.h

#ifndef CAMERA_H
#define CAMERA_H

#include <cmath>

#include "vec3.h"

class Camera {
public:
  Camera(Point3 lookfrom,
          Point3 lookat,
          Vec3 vup,
          double vfov, // vertical field-of-view in degrees
          double aspect_ratio) {
    auto theta = degrees_to_radians(vfov);
    auto h = std::tan(theta/2);
    auto viewport_height = 2.0 * h;
    auto viewport_width = aspect_ratio * viewport_height;

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

    origin = lookfrom;
    horizontal = viewport_width * u;
    vertical = viewport_height * v;
    lower_left_corner = origin - horizontal / 2 - vertical / 2 - w;
  }

  Ray get_ray(double u, double v) const {
    return Ray(origin, lower_left_corner + u * horizontal + v * vertical - origin);
  }

private:
  Point3 origin;
  Point3 lower_left_corner;
  Vec3 horizontal;
  Vec3 vertical;
};

#endif // CAMERA_H