当我们在构造复杂的3D事物的时候，如果能够组织独立元素就太方便了。比如说，你想创造一个孩子的手臂：你就需要确定哪一部分是孩子的手腕，哪一部分是孩子的前臂，哪一部分是孩子的肘，哪一部分是孩子的上臂，哪一部分是孩子的肩膀等等。
当然是允许独立地移动每个区域的啦。以肘为指点会移动前臂和手，而不是肩膀。Core Animation图层很容易就可以让你在2D环境下做出这样的层级体系下的变换，但是3D情况下就不太可能，因为所有的图层都把他的孩子都平面化到一个场景中
CATransformLayer解决了这个问题，CATransformLayer不同于普通的CALayer，因为它不能显示它自己的内容。只有当存在了一个能作用域子图层的变换它才真正存在。CATransformLayer并不平面化它的子图层，所以它能够用于构造一个层级的3D结构
gitHub地址在transform/TransformLayer里面
为了作对比，这里先用UIView来实现一个正方体。下面是代码：
首先用Interface Builder布局正方体的六个面，如图：
正方体的六个面
然后将这六个正方体的面添加到
@property (strong, nonatomic) IBOutletCollection(UIView) NSArray *faces;
中。
在3号上面添加了一个按钮，添加按钮方法：
- (IBAction)click:(UIButton *)sender;
.m中代码：
//将正方体的六个面添加到self.view上，并创建face.layer的transform
- (void)addFace:(NSInteger)index withTransform:(CATransform3D)transform{
//get the face view and add it to the container”
UIView * face = self.faces[index];
//如果添加face的时候，3号不是最后添加的话，则button的按钮点击事件会被拦截，虽然变换了位置；可以设置其他界面的userInteractionEnabled为NO；或者最后一个添加3号视图
// if (index != 2) {
// face.userInteractionEnabled = NO;
// }
[self.view addSubview:face];
//center the face view within the container
CGSize containerSize = self.view.bounds.size;
face.center = CGPointMake(containerSize.width/2, containerSize.height/2);
//apply the transfrom
face.layer.transform = transform;
face.layer.borderWidth = .5;
}
接下来就是设置六个面的transform：
//设置正方体的六个面的transform
-(void)transforms{
/**
*ios上坐标系规则为：x轴右边为正，y轴下边为正，z轴前面为正
*/
//add cube face 1(正方体前面)
CATransform3D transform = CATransform3DMakeTranslation(0, 0, kLength);
[self addFace:0 withTransform:transform];
//add cube face 2（正方体右面）
transform = CATransform3DMakeTranslation(kLength, 0, 0);
transform = CATransform3DRotate(transform, M_PI_2, 0, 1, 0);
[self addFace:1 withTransform:transform];
//add cube face 4(正方体下面)
transform = CATransform3DMakeTranslation(0, kLength, 0);
transform = CATransform3DRotate(transform, -M_PI_2, 1, 0, 0);
[self addFace:3 withTransform:transform];
//add cube face 5(正方体左边)
transform = CATransform3DMakeTranslation(-kLength, 0, 0);
transform = CATransform3DRotate(transform, -M_PI_2, 0, 1, 0);
[self addFace:4 withTransform:transform];
//add cube face 6(正方体后面）
transform = CATransform3DMakeTranslation(0, 0, -kLength);
transform = CATransform3DRotate(transform, M_PI, 0, 1, 0);
[self addFace:5 withTransform:transform];
//add cube face 3（正方体上面）
transform = CATransform3DMakeTranslation(0, -kLength, 0);
transform = CATransform3DRotate(transform, M_PI_2, 1, 0, 0);
[self addFace:2 withTransform:transform];
}
调用
[self transforms];
实现效果为：
正方体1
如图所示，根本看不出来是一个正方体，所以下面要对self.view.layer的perspective变换矩阵
CATransform3D perspective = CATransform3DIdentity;
perspective.m34 = -1.0/500.0;
//// //绕着X轴向左旋转45度
perspective = CATransform3DRotate(perspective, -M_PI_4, 1, 0, 0);
//// //绕着Y轴向下旋转45度
perspective = CATransform3DRotate(perspective, -M_PI_4, 0, 1, 0);
self.view.layer.sublayerTransform = perspective;
显示效果：
正方体2
这个是通过view改变layer的transform来显示正方体的。
2、通过CATransformLayer来实现正方体
//创建layer并设置背景色和transform
-(CALayer *)faceWithTransform:(CATransform3D)transform{
CALayer * face = [CALayer layer];
face.frame = CGRectMake(-50, -50, 100, 100);
CGFloat red = (rand()/(double)INT_MAX);
CGFloat green = (rand()/(double)INT_MAX);
CGFloat blue = (rand()/(double)INT_MAX);
face.backgroundColor = [UIColor colorWithRed:red green:green blue:blue alpha:1].CGColor;
face.transform = transform;
return face;
}
//创建transformLayer，并添加layer
-(CALayer*)cubeWithTransform:(CATransform3D)transform{
//create cube layer
CATransformLayer * cube = [CATransformLayer layer];
//add cube face 1，Z轴位移50
CATransform3D ct = CATransform3DMakeTranslation(0, 0, 50);
[cube addSublayer:[self faceWithTransform:ct]];
//add cube face 2，Z轴位移-50，Y轴旋转M_PI
ct = CATransform3DMakeTranslation(0, 0, -50);
ct = CATransform3DRotate(ct, M_PI, 0, 1, 0);
[cube addSublayer:[self faceWithTransform:ct]];
//add cube face 3,X轴位移50，Y轴旋转M_PI_2
ct = CATransform3DMakeTranslation(50, 0, 0);
ct = CATransform3DRotate(ct, M_PI_2, 0, 1, 0);
[cube addSublayer:[self faceWithTransform:ct]];
//add cube face 4,X轴位移-50，Y轴旋转-M_PI_2
ct = CATransform3DMakeTranslation(-50, 0, 0);
ct = CATransform3DRotate(ct, -M_PI_2, 0, 1, 0);
[cube addSublayer:[self faceWithTransform:ct]];
//add cube face 5,Y轴位移50，X轴旋转M_PI_2
ct = CATransform3DMakeTranslation(0, 50, 0);
ct = CATransform3DRotate(ct, M_PI_2, 1, 0, 0);
[cube addSublayer:[self faceWithTransform:ct]];
//add cube face 6,Y轴位移-50，X轴旋转-M_PI_2
ct = CATransform3DMakeTranslation(0, -50, 0);
ct = CATransform3DRotate(ct, -M_PI_2, 1, 0, 0);
[cube addSublayer:[self faceWithTransform:ct]];
CGSize containerSize = self.view.bounds.size;
cube.position = CGPointMake(containerSize.width/2.0, containerSize.height/2.0);
cube.transform = transform;
return cube;
}
调用：
// CATransformLayer
// 创建第一个cube
CATransform3D ct1 = CATransform3DIdentity;
//x轴位移
ct1 = CATransform3DTranslate(ct1, -100, 0, 0);
//创建cube的六个面
CALayer * cube1 = [self cubeWithTransform:ct1];
[self.view.layer addSublayer:cube1];
// 创建第二个cube
CATransform3D ct2 = CATransform3DIdentity;
//x轴平移100
ct2 = CATransform3DTranslate(ct2, 100, 0, 0);
//绕着X轴旋转-45
ct2 = CATransform3DRotate(ct2, -M_PI_4, 1, 0, 0);
//绕着Y轴旋转-45
ct2 = CATransform3DRotate(ct2, -M_PI_4, 0, 1, 0);
CALayer * cube2 = [self cubeWithTransform:ct2];
[self.view.layer addSublayer:cube2];
显示效果:
正方体3