From the release notes/upgrade guide of OpenCASCADE 7.0.0:
Correction of interpretation of Euler angles in gp_Quaternion
Conversion of gp_Quaternion to and from intrinsic Tait-Bryan angles (including gp_YawPitchRoll) is fixed.
Before that fix the sequence of rotation axes was opposite to the intended; e.g. gp_YawPitchRoll (equivalent to gp_Intrinsic_ZYX) actually defined intrinsic rotations around X, then Y, then Z. Now the rotations are made in correct order.
Applications that use gp_Quaternion to convert Yaw-Pitch-Roll angles (or other intrinsic Tait-Bryan sequences) may need to be updated to take this change into account.
What does this exactly mean? What do I have to do if I am using the methods "GetEulerAngles" and "SetEulerAngles" from gp_Quaternion when I am upgrading from 6.9.1 to 7.0.0? I am always using "gp_Intrinsic_XYZ", do I have to change this (to what?) to achieve the same results as in 6.9.1?