How to animate UIImageViews like hatch doors opening - ios

Question

I'm trying to create an animation that would look like 2 french doors (or 2 hatch doors) opening towards the user.
I tried using the built in UIViewAnimationOptionTransitionFlipFromRight transition, but the origin of the transition seems to be the center of the UIImageView rather than the left edge. Basically I have 2 UIImageViews that each fill have the screen. I would like the animation to look like the UIImageViews are lifting from the center of the screen to the edges.
[UIView transitionWithView:leftView
duration:1.0
options:UIViewAnimationOptionTransitionFlipFromRight
animations:^ { leftView.alpha = 0; }
completion:^(BOOL finished) {
[leftView removeFromSuperview];
}];
Has anyone done something like this before? Any help would be awesome!
UPDATE:
Working code thanks to Nick Lockwood
leftView.layer.anchorPoint = CGPointMake(0, 0.5); // hinge around the left edge
leftView.frame = CGRectMake(0, 0, 160, 460); //reset view position
rightView.layer.anchorPoint = CGPointMake(1.0, 0.5); //hinge around the right edge
rightView.frame = CGRectMake(160, 0, 160, 460); //reset view position
[UIView animateWithDuration:0.75 animations:^{
CATransform3D leftTransform = CATransform3DIdentity;
leftTransform.m34 = -1.0f/500; //dark magic to set the 3D perspective
leftTransform = CATransform3DRotate(leftTransform, -M_PI_2, 0, 1, 0);
leftView.layer.transform = leftTransform;
CATransform3D rightTransform = CATransform3DIdentity;
rightTransform.m34 = -1.0f/500; //dark magic to set the 3D perspective
rightTransform = CATransform3DRotate(rightTransform, M_PI_2, 0, 1, 0);
rightView.layer.transform = rightTransform;
}];

Answer 1

First add the QuartzCore library to your project and #import <QuartzCore/QuartzCore.h>
Every view has a layer property with sub-properties that are animatable. This is where you'll find all the really cool stuff when it comes to animation capabilities (I suggest reading up on the CALayer class properties you can set - it will blow your mind - dynamic soft drop shadows on any view?)
Anyway, back on topic. To rotate your doors open in 3D, first position them as if they were closed, so with each door filling half the screen.
Now set their view.layer.anchorPoint properties as follows
leftDoorView.layer.anchorPoint = CGPoint(0, 0.5); // hinge around the left edge
rightDoorView.layer.anchorPoint = CGPoint(1.0, 0.5); // hinge around the right edge
Now apply the following animation
[UIView animateWithDuration:0.5 animations:^{
CATransform3D leftTransform = CATransform3DIdentity;
leftTransform.m34 = -1.0f/500; //dark magic to set the 3D perspective
leftTransform = CATransform3DRotate(leftTransform, M_PI_2, 0, 1, 0); //rotate 90 degrees about the Y axis
leftDoorView.layer.transform = leftTransform;
//do the same thing but mirrored for the right door, that probably just means using -M_PI_2 for the angle. If you don't know what PI is, Google "radians"
}];
And that should do it.
DISCLAIMER: I've not actually tested this, so the angles may be backwards, and the perspective may be screwy, etc. but it should be a good start at least.
UPDATE: Curiosity got the better of me. Here is fully working code (this assumes that the left and right doors are laid out in the closed position in the nib file):
- (void)viewDidLoad
{
[super viewDidLoad];
leftDoorView.layer.anchorPoint = CGPointMake(0, 0.5); // hinge around the left edge
leftDoorView.center = CGPointMake(0.0, self.view.bounds.size.height/2.0); //compensate for anchor offset
rightDoorView.layer.anchorPoint = CGPointMake(1.0, 0.5); // hinge around the right edge
rightDoorView.center = CGPointMake(self.view.bounds.size.width,self.view.bounds.size.height/2.0); //compensate for anchor offset
}
- (IBAction)open
{
CATransform3D transform = CATransform3DIdentity;
transform.m34 = -1.0f/500;
leftDoorView.layer.transform = transform;
rightDoorView.layer.transform = transform;
[UIView animateWithDuration:0.5 animations:^{
leftDoorView.layer.transform = CATransform3DRotate(transform, M_PI_2, 0, 1, 0);
rightDoorView.layer.transform = CATransform3DRotate(transform, -M_PI_2, 0, 1, 0);
}];
}
- (IBAction)close
{
[UIView animateWithDuration:0.5 animations:^{
CATransform3D transform = CATransform3DIdentity;
transform.m34 = -1.0f/500;
leftDoorView.layer.transform = transform;
rightDoorView.layer.transform = transform;
}];
}