def box3d_to_2d(box3d):
    """
    Convert 3D bounding box to 2D.

    Parameters
    ----------
    box3d : np.ndarray
        (n, 8, 3)

    Returns
    -------
    box2d : np.ndarray
        (n, 4, 2), project 3d to 2d.
    """
    box2d = box3d[:, :4, :2]
    return box2d