ofxFaceTracker2 head polyline without the rotation

Hello,

I’m using ofxFaceTracker2 for a project.
I can’t get the ofPolyline of the head without having also its rotation,
like it’s possible to do in ofxFaceTracker.

I tried to apply the inverse matrix of getPoseMatrix() from ofPolyline, but it doesn"t give me what I want.

Thank you for your help.