quaternion.py 文件源码

def angle(vector1, vector2):
    """Return the angle between vector1 and vector2 in radians [0, pi]."""
    u1 = vector1.normalize()
    u2 = vector2.normalize()
    cosine = u1 * u2
    if cosine == 1.0:
        return 0
    elif cosine == -1.0:
        return math.pi
    elif cosine == 0.0:
        return math.pi/2

    # Unit vectors: sine == sqrt(1.0 ** 2 - cosine ** 2) if angle within [0, pi]
    tangent = math.sqrt(1.0 - cosine * cosine) / cosine

    return math.atan(tangent)