implementing quaternions to euler angle conversion in python

Question

I am trying to write a custom function that takes a quaternion and outputs the Euler angles. I thought it was quite easy: I am using the formulas found here while also looking at the C++ implementation in the same page. The function looks like this:

import math    
def quaternion_to_euler(quaternion: tuple):
        w, x, y, z = quaternion
        roll = math.atan2(2*(w*x + y*z), 1 - 2*(x * x + y * y))
        pitch = math.asin(2*(w*y - z*x))
        yaw = math.atan2(2*(w*z + x*y), 1 - 2*(y * y + z * z))
        return(roll, pitch, yaw)

To be sure of having the good results, I am comparing my conversion with the one performed by this page .

It seems that my results are completely off. As an example compare the results of my function for a specific quaternion:

quaternion = (0.73007, -0.03484,  0.68173,  0.03199)
roll, pitch, yaw = quaternion_to_euler(quaternion)
print(f'roll: {roll}, pitch: {pitch}, yaw: {yaw}')
roll: -0.10618318122804299, pitch: 1.5022308055111253, yaw: -0.011586976613645479

To the results of the page linked above:

roll: -0.9466037, pitch: 1.454085, yaw: 0.9425664

The formulas seem quite straightforward to me, and I cannot see any self-evident mistake in the implementation. Can someone explain to me what I am doing wrong?

Answer 1

For Euler angles, the rotation order matters.

It seems that your reference Euler angles result is XYZ ordered rotation but your result is ZYX ordered rotation.

The page whose link you provided also mentions about it around 'Body 3-2-1 sequence' parts.