title: iOS Core Animation Value Interpolation
body: <p>As I know, putting it simply, Core Animation actually works by interpolating property value over time. Given this, is there any way to interpolate the property to a specific time? For example I have animation</p>
  
  <pre><code>animation = [CABasicAnimation animationWithKeyPath:@"opacity"];
  animation.duration = 1.0;
  animation.fromValue = [NSNumber numberWithFloat:0.0];
  animation.toValue = [NSNumber numberWithFloat:1.0];
  </code></pre>
  
  <p>Is there a way to freeze the layer at, say, 0.5 seconds when the opacity value is also 0.5?</p>
  
  <p>If there's no way to do it with Core Animation, are there any tweening library for objective-c that allows this?</p>