Open Radar

 
Summary:
The SCNMaterialProperty.contents documentation simply states that the contents is animatable and lists UIImage/NSImage/CGImageRef as possible value types, however trying to do so does not work as expected.

Steps to Reproduce:
I’ve tried an implicit animation, in which case it immediately shows the ‘after’ image:

    node.geometry.firstMaterial.diffuse.contents = [UIImage imageNamed:@"before"];
    [SCNTransaction begin];
    [SCNTransaction setAnimationDuration:5];
    node.geometry.firstMaterial.diffuse.contents = [UIImage imageNamed:@"after"];
    [SCNTransaction commit];

An explicit animation, which does nothing:

    CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"contents"];
    animation.fromValue = (__bridge id)[UIImage imageNamed:@"before"].CGImage;
    animation.toValue = (__bridge id)[UIImage imageNamed:@"after"].CGImage;
    animation.duration = 5;
    [node.geometry.firstMaterial.diffuse addAnimation:animation forKey:nil];

As well as through a `CALayer`, which does nothing:

    CALayer *textureLayer = [CALayer layer];
    textureLayer.frame = CGRectMake(0, 0, 793, 1006);
    textureLayer.contents = (__bridge id)[UIImage imageNamed:@"before"].CGImage;
    node.geometry.firstMaterial.diffuse.contents = textureLayer;
    
    CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"contents"];
    animation.fromValue = (__bridge id)[UIImage imageNamed:@"before"].CGImage;
    animation.toValue = (__bridge id)[UIImage imageNamed:@"after"].CGImage;
    animation.duration = 5;
    [textureLayer addAnimation:animation forKey:nil];

Expected Results:
A crossfade animation between the two images.

Actual Results:
It either shows just the first or the second texture.

Documentation:
https://developer.apple.com/library/prerelease/ios/documentation/SceneKit/Reference/SCNMaterialProperty_Class/index.html#//apple_ref/occ/instp/SCNMaterialProperty/contents