message: Map from cartesian to spherical coords
diff: @@ -133,8 +133,8 @@ inline auto get_tex_coord(HR const& hr, basic_sphere<T> const& sphere)
  auto n = (hr.isect_pos - sphere.center) / sphere.radius;
  return vector<2, S>(
  - atan2(n.x, n.z) / constants::two_pi<S>() + S(0.5),
  - n.y * S(0.5) + S(0.5)
  + acos(n.z),
  + atan(n.y / n.x)
  );
  }
  