Custom view transition in OpenGL ES

Question

I\'m trying to create a custom transition, to serve as a replacement for a default transition you would get here, for example:

[self.navigationController pushVie         


        

Answer 1

I think the function you might be thinking of is http://www.opengl.org/sdk/docs/man/xhtml/glCopyTexImage2D.xml ... you set the viewport to the texture size and then draw as usual, then do glCopyTexImage2D to copy the scene onto a texture.

or you should look into FrameBuffer Objects. The default OpenGL template in XCode uses these. Just generate the example project to see how those work.

Answer 2

While I cannot completely answer your question without doing some more research of my own, I can help a bit:

-In order to get the view of a UINavigationController, you need to take a screenshot. The easiest way to do this is by grabbing it into a UIImage:

UIGraphicsBeginImageContext(self.view.frame.size);
[[self.view layer] renderInContext:UIGraphicsGetCurrentContext()];
UIImage* test = UIGraphicsGetImageFromCurrentImageContext();
UIImageView* view = [[UIImageView alloc] initWithImage:test];
UIGraphicsEndImageContext();

I am not sure if you can render a GLContext (not familiar on the phone) into a CGImage, but I would do something like that (and init a UIImage from that). I would prerender every frame of the animation you are trying to do and slap it into an UIImageView using the animation stuff provided within. That is, if your animation is simple enough. Otherwise, it might come down to writing your own animation function :-/

Answer 3

I recently write some transitioning animation betweeen view controllers like you. If you want to get any extra info from the invisible view, you can try delaying the transition like this :

- (void)animationFromModalView:(UIView *)modalView toMasterView:(UIView *)masterView
{

[masterView setNeedsLayout];
[masterView layoutIfNeeded];

[self performSelector:@selector(delayAnimationFromModalViewToMasterView) withObject:nil afterDelay:.1f];
}

Answer 4

I have just put together a transition class to implement your own transition animation in OpenGL ES.

Feel free to read about it here

There are two example transitions in the project, feel free to add you own to it.