好尴尬，按照套路，我点进了CATransformLayer.h，但是空空如也，什么也没有。那么CATransfromLayer的作用是啥呢？只能通过撸代码来体会了。

//先上效果图吧

对比效果吧

部分代码

绘制立方体

    //面1
    transfrom = CATransform3DMakeTranslation(0, 0, sub_width/2);
    [cube addSublayer:[self layerWithTransform:transfrom]];
    
    //面2
    transfrom = CATransform3DMakeTranslation(0, 0, -sub_width/2);
    [cube addSublayer:[self layerWithTransform:transfrom]];
    
    //面3
    transfrom = CATransform3DMakeTranslation(sub_width/2, 0, 0);
    transfrom = CATransform3DRotate(transfrom, M_PI_2, 0, 1, 0);
    [cube addSublayer:[self layerWithTransform:transfrom]];
    
    //面4
    transfrom = CATransform3DMakeTranslation(-sub_width/2, 0, 0);
    transfrom = CATransform3DRotate(transfrom, -M_PI_2, 0, 1, 0);
    [cube addSublayer:[self layerWithTransform:transfrom]];
    
    
    //面5
    transfrom = CATransform3DMakeTranslation(0, sub_width/2, 0);
    transfrom = CATransform3DRotate(transfrom, M_PI_2, 1, 0, 0);
    [cube addSublayer:[self layerWithTransform:transfrom]];

    //面6
    transfrom = CATransform3DMakeTranslation(0, -sub_width/2, 0);
    transfrom = CATransform3DRotate(transfrom, -M_PI_2, 1, 0, 0);
    [cube addSublayer:[self layerWithTransform:transfrom]];

动画

    static float degree = 0.f;
    
    CGFloat duration = 1.f;
    CGFloat singleDuration = 1 / (duration * 60.0);
    CGFloat singleDegree = 45/(duration * 60.0);
    
    
    CATransform3D fromValue = CATransform3DIdentity;
    fromValue.m34 = -1/500;
    fromValue = CATransform3DRotate(fromValue, DEGREE(degree), 0, 1, 0);
    
    CATransform3D toValue = CATransform3DIdentity;
    toValue.m34 = -1/500;
    toValue = CATransform3DRotate(toValue, DEGREE(degree += singleDegree), 0, 1, 0);
    
    //使用transform无法实现旋转2*M_PI，此时可以使用虚拟属性@"transform.rotation.y",可以使用相对值旋转byValue
    CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"transform"];
    animation.duration = singleDuration;
    animation.fromValue = [NSValue valueWithCATransform3D:fromValue];
    animation.toValue = [NSValue valueWithCATransform3D:toValue];
    animation.repeatCount = HUGE_VALL;
    animation.removedOnCompletion = NO;
    animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
    [layer addAnimation:animation forKey:@"transform"];

结论：CATransformLayer可以为他的子图层，统一提供景深效果。(如有错误，请指正。如需源码，请点赞留言)