Update the model layer before adding the animation.
CABasicAnimation* fadeAnim = [CABasicAnimation animationWithKeyPath:@"opacity"];
fadeAnim.fromValue = [NSNumber numberWithFloat:1.0];
fadeAnim.toValue = [NSNumber numberWithFloat:0.0];
fadeAnim.duration = 5.0;
// Change the actual data value in the layer to the final value.
theLayer.opacity = 0.0;
[theLayer addAnimation:fadeAnim forKey:@"opacity"];