def strRT(R, T):
    """Returns a string for a rotation/translation pair in a readable form.
    """
    x  = "[%6.3f %6.3f %6.3f %6.3f]\n" % (
        R[0,0], R[0,1], R[0,2], T[0])
    x += "[%6.3f %6.3f %6.3f %6.3f]\n" % (
        R[1,0], R[1,1], R[1,2], T[1])
    x += "[%6.3f %6.3f %6.3f %6.3f]\n" % (
        R[2,0], R[2,1], R[2,2], T[2])

    return x