Why R is not considered in cv2.undistortPoints?

Python
,
5

Although R is changed to a large one and both R and P are given, the same issue still exists.

pts=np.array([[  0., 639.,   0., 639.],
              [  0.,   0., 479., 479.],
              [  1.,   1.,   1.,   1.]])
K=np.array([[536.86303957,   0.        , 338.54127669],
            [  0.        , 537.17967509, 231.541806  ],
            [  0.        ,   0.        ,   1.        ]])

R=cv2.Rodrigues(np.array([-.1,.1,.3]))[0]

P=np.array([[538.40307187,   0.        , 341.6945076 ,    0.        ],
             [  0.        , 538.40307187, 243.63676453,   0.        ],
             [  0.        ,   0.        ,   1.        ,   0.        ]])

#only R is given without P
pts_0=cv2.undistortPoints(pts[:2], K, None, None, None)
pts_1=cv2.undistortPoints(pts[:2], K, None, R, None)
print(np.allclose(pts_0, pts_1)) #True

#both R and P are given
pts_2=cv2.undistortPoints(pts[:2], K, None, R, P[:3,:3]) 
temp=np.ones((3,4))
temp[:2]=pts_0.squeeze().T
temp=P[:3,:3]@temp
print(np.allclose(temp[:2]/temp[-1],pts_2.squeeze().T)) #True