Added extinction coefficient

src/camera.cpp

@@ -25,5 +25,5 @@ camera::camera(double aspect_ratio, double viewport_height, double viewport_widt
 
 ray camera::get_ray(double u, double v) const{
   //return ray(origin, lower_left_corner + u*horizontal + v*vertical - origin);
-  return ray(lower_left_corner + u*horizontal + v*vertical, unit_vector(lower_left_corner + u*horizontal + v*vertical - origin), 1., 0., 1., 0, max_bounces);
+  return ray(lower_left_corner + u*horizontal + v*vertical, unit_vector(lower_left_corner + u*horizontal + v*vertical - origin), 1., 0., 1., 0., 0, max_bounces);
 }