you're actually trying to identify in some sense you're trying to do inverse graphics of the camera parameters here which the only parameter you care about is the rotation angle here but but since it's physically grounded it's gonna learn something useful so here is how they implemented it which is you take an image be rotated by various possible angles and you can struck these rotated versions you pass them to the same convolutional neural network and it is pretty clear rotation angle so you just do it for all possible images in your