Function cart_to_oblate_position

examples/pde/bhrt.cpp:277–295

* @brief Transform the position vectors from cartesian to oblate coordinates * * @param vel * @param pos * @return af::array */

 * @return af::array
 */
af::array cart_to_oblate_position(const af::array& pos) {
    if (pos.dims()[0] != 3)
        throw make_error("Arrays must have 3 principal coordintes");

    af::array x = pos(0, af::span);
    af::array y = pos(1, af::span);
    af::array z = pos(2, af::span);
    auto a      = J / M;
    auto diff   = x * x + y * y + z * z - a * a;

    af::array r =
        af::sqrt((diff + af::sqrt(diff * diff + z * z * a * a * 4.0)) / 2.0);
    af::array o = af::acos(z / r);
    af::array p = af::atan2(y, x);

    af::array transformed_pos = af::join(0, r, o, p);

    return transformed_pos;
}

/**
 * @brief Transform the position vectors from oblate to cartesian coordinates