// move the camera on the upper layer
camera.x += cam_to_target.x * intersect;
camera.y += cam_to_target.y * intersect;
camera.z += cam_to_target.z * intersect;

camera_depth.x = 0.0f;
camera_depth.y = 0.0f;
camera_depth.z = 0.0f;
camera_depth.w = 0.0f;