def compute_pelvis_origin(left_asis, right_asis):
    """
    Compute the origin of the pelvis.

    Parameters
    ----------
    left_asis : numpy.ndarray
        1 or 2D (Nx3) array of positions of the left asis marker.
    right_asis : numpy.ndarray
        1 or 2D (Nx3) array of positions of the right asis marker.

    Returns
    -------
    origin : numpy.ndarray
        Array of the position of the pelvis origin.

    References
    ----------
    Ren et al.  "Whole body inverse dynamics over a complete gait cycle based only on measured kinematics."
    *J. of Biomech*. 2008
    """
    origin = (left_asis + right_asis) / 2
    return origin
