One unit forward vector, drawn from the side and from above at the same time. The circle on the right has radius cos(pitch).
What to notice. Push pitch toward 90° and the plan-view circle collapses to a point —
that is the whole of cp in one picture. Nothing about yaw changes, but there is less and less for it to spin.
Turn off the clamp and the red right-vector loses its length entirely at the pole: the cross product with world-up has
no answer there, which is why mouselook goes berserk if you forget to clamp.