Hi Pierre,
The phenomenon you're experiencing is likely due to the issue of gimbal lock, which occurs when two of the three axes in a 3D rotation system become aligned, causing a loss of one degree of freedom.
To avoid this issue and get a more accurate representation of the rotation around the r2 axis (pitch), you can use alternative representations of rotations that do not suffer from gimbal lock. Here are a few suggestions:
1. Use Quaternions Directly
Instead of converting quaternions to Euler angles, you can work with quaternions directly. Quaternions provide a robust and gimbal-lock-free way to represent rotations. If you need to visualize or interpret the rotation, you can extract the relevant information directly from the quaternion.
2. Use Rotation Matrices
Another approach is to use rotation matrices, which also do not suffer from gimbal lock. You can convert the quaternion to a rotation matrix and then analyze the matrix to understand the rotation.
3. Use Alternative Angle Representations
If you need to work with angles, consider using other representations such as tilt angles or axis-angle representation, which can provide more intuitive and gimbal-lock-free descriptions of rotations.
Hope this helps.
