CAAnimation with an transform rotation over an point - ios

Question

I'm trying to animate the rotation of a layer of a view over an arbitrary point. The start position of the animation will be a 90º rotation from the end and final position. This view occupies all the screen except the status bar.
I'm trying to use the following code (with a translation, followed by a rotation and an anti translation) but, however starting and ending in it, the animation isn't centered on the point, but wobbles around it.
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:#"transform"];
animation.duration = 1;
animation.additive = YES;
animation.removedOnCompletion = YES;
animation.fillMode = kCAFillModeRemoved;
//The point that should be used as the center of rotation
CGPoint cursorCenter=self.angleCenter;
//The center of the view
CGPoint linesCenter=lines.center;
//The transformation: translate->rotate->anti-translate
CATransform3D transform = CATransform3DIdentity;
transform = CATransform3DTranslate(transform, cursorCenter.x-linesCenter.x, cursorCenter.y-linesCenter.y, 0.0);
transform = CATransform3DRotate(transform, degreesToRadians(-90), 0.0, 0.0, -1.0);
transform = CATransform3DTranslate(transform, linesCenter.x-cursorCenter.x, linesCenter.y-cursorCenter.y, 0.0);
animation.fromValue =[NSValue valueWithCATransform3D:transform];
animation.toValue =[NSValue valueWithCATransform3D:CATransform3DIdentity];
[lines.layer addAnimation:animation forKey:#"90rotation"];
What I'm doing wrong?

Answer 1

You don't have to make translations to rotate over a aspecific point. Just change the anchorPoint of the layer to adjust center of the rotation.
The origin of the transform is the value of the center property, or
the layer’s anchorPoint property if it was changed.
About anchor point and how to specify it:
You specify the value for this property using the unit coordinate
space. The default value of this property is (0.5, 0.5), which
represents the center of the layer’s bounds rectangle. All geometric
manipulations to the view occur about the specified point. For
example, applying a rotation transform to a layer with the default
anchor point causes the layer to rotate around its center. Changing
the anchor point to a different location would cause the layer to
rotate around that new point.
Based on CALayer Class Reference and Core Animation Programming Guide