POPLayerSetRotationY(self.frontView.layer, POPDegreesToRadians(progress));
outputs error:
Implicit declaration of function 'POPLayerSetRotationY' is invalid in C99
Will need more information to look into this — are you importing the header defining that function? (I'm assuming this is in your code, not Pop itself.)
POPLayerSetRotationY(self.frontView.layer, POPDegreesToRadians(progress));
outputs error:Implicit declaration of function 'POPLayerSetRotationY' is invalid in C99