The registration problem for the yaw component is the same as in Section 9.2. The forward direction may be chosen from the initial orientation of the rigid body or it could be determined with respect to a fixed direction in the world. The pitch and roll components should be determined so that they align with gravity. The virtual world should not appear to be tilted with respect to the real world (unless that is the desired effect, which is rarely the case).

Steven M LaValle 2020-01-06