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pythonscipyrotational-matrices

measure difference between rotation matrix

I have two rotation matrix suppose initial basis O is identity in R^3 and rotation RAO transforms a point in O into basis A and rotation RBO transforms a point in O into basis B

I tried to calculate angle differences between RAO and RBO like:

from scipy.spatial.transform import Rotation
def Rdiff(RAO, RBO):
    RBA = RAO.T @ RBO
    RBA = Rotation.from_matrix(RBA)
    return RBA.as_euler('zyx', degrees=True)

RAO = Rotation.from_euler('zyx', [10, 0, 13],                 
degrees=True).as_matrix()    
RBO = Rotation.from_euler('zyx', [0, 63, 40], 
degrees=True).as_matrix()

print(Rdiff(RAO, RBO))

but the result:

[-16.65056217  57.31794707  41.4856089 ]

is different from what I expected: [-10, 63, 26]
Is that something wrong here? How can I fix it?

[EDIT] I used math formula from here: https://math.stackexchange.com/questions/87338/change-in-rotation-matrix/87698#comment4515183_87698 and I have checked that RAO, RBO, RBA in function Rdiff is unitary.

[EDIT] My original function in Rdiff is fault, so I changed line:

RBA = RBO @ RAO.T

into

RBA = RAO.T @ RBO
Solution

  • Your code seems fine. The issue is that when you compose two rotations with given Euler angles, then you don't simply get a rotation given by the sums of these angles.