I am wondering what is the best way to implement rotation-based dragging movements in my iPhone application. I have a UIView that I wish to rotate around its centre, when the users finger is touch the view and they move it. Think of it like a dial that needs to be adjusted with the finger. The basic question comes down to: 1) Should I remember the initial angle and transform when touchesBegan is called, and then every time touchesMoved is called apply a new transform to the view based on the current position of the finger, e.g., something like: - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [touches anyObject]; CGPoint currentPoint = [touch locationInView:self]; //current position of touch if (([touch view] == self) && [Utility getDistance:currentPoint toPoint:self.middle] <= ROTATE_RADIUS //middle is centre of view && [Utility getDistance:currentPoint toPoint:self.middle] >= MOVE_RADIUS) { //will be rotation gesture //remember state of view at beginning of touch CGPoint top = CGPointMake(self.middle.x, 0); self.initialTouch = currentPoint; self.initialAngle = angleBetweenLines(self.middle, top, self.middle, currentPoint); self.initialTransform = self.transform; } } - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{ UITouch *touch = [touches anyObject]; CGPoint currentPoint = [touch locationInView:self]; //current position of touch if (([touch view] == self) && [Utility getDistance:currentPoint toPoint:self.middle] <= ROTATE_RADIUS && [Utility getDistance:currentPoint toPoint:self.middle] >= MOVE_RADIUS) { //a rotation gesture //rotate tile float newAngle = angleBetweenLines(self.middle, CGPointMake(self.middle.x, 0), self.middle, currentPoint); //touch angle float angleDif = newAngle - self.initialAngle; //work out dif between angle at beginning of touch and now. CGAffineTransform newTransform = CGAffineTransformRotate(self.initialTransform, angleDif); //create new transform self.transform = newTransform; //apply transform. } OR 2) Should I simply remember the last known position/angle, and rotate the view based on the difference in angle between that and now, e.g.,: - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [touches anyObject]; CGPoint currentPoint = [touch locationInView:self]; //current position of touch if (([touch view] == self) && [Utility getDistance:currentPoint toPoint:self.middle] <= ROTATE_RADIUS && [Utility getDistance:currentPoint toPoint:self.middle] >= MOVE_RADIUS) { //will be rotation gesture //remember state of view at beginning of touch CGPoint top = CGPointMake(self.middle.x, 0); self.lastTouch = currentPoint; self.lastAngle = angleBetweenLines(self.middle, top, self.middle, currentPoint); } } - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{ UITouch *touch = [touches anyObject]; CGPoint currentPoint = [touch locationInView:self]; //current position of touch if (([touch view] == self) && [Utility getDistance:currentPoint toPoint:middle] <= ROTATE_RADIUS && [Utility getDistance:currentPoint toPoint:middle] >= MOVE_RADIUS) { //a rotation gesture //rotate tile float newAngle = angleBetweenLines(self.middle, CGPointMake(self.middle.x, 0), self.middle, currentPoint); //touch angle float angleDif = newAngle - self.lastAngle; //work out dif between angle at beginning of touch and now. CGAffineTransform newTransform = CGAffineTransformRotate(self.transform, angleDif); //create new transform self.transform = newTransform; //apply transform. self.lastTouch = currentPoint; self.lastAngle = newAngle; } The second option makes more sense to me, but it is not giving very pleasing results (jaggy updates and non-smooth rotations). Which way is best (if any), in terms of performance? Cheers!