在做3D事物的时候，我们都需要做出独立的3D效果，在前面的博客中，我们画过一个3D的立方体，但是它却并不是独立的，而是由放在主视图上的6张子视图通过平移旋转得到的，这里通过CATransformLayer我们可以得到完全独立的3D图形，可以直接对整个3D事物进行一些操作。需要说明的是CATransformLayer并不显示自身的内容，只有当存在了一个作用域子图层时才会显示子图层的变换，CATransformLayer才真正存在，类似于一个画布。
- (CALayer *)faceWithTransform:(CATransform3D)transform { //create cube face layer CALayer *face = [CALayer layer]; face.frame = CGRectMake(-50, -50, 100, 100); //apply a random color 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:1.0].CGColor; face.transform = transform; return face; } - (CALayer *)cubeWithTransform:(CATransform3D)transform { //create cube layer CATransformLayer *cube = [CATransformLayer layer]; //add cube face 1 CATransform3D ct = CATransform3DMakeTranslation(0, 0, 50); [cube addSublayer:[self faceWithTransform:ct]]; //add cube face 2 ct = CATransform3DMakeTranslation(50, 0, 0); ct = CATransform3DRotate(ct, M_PI_2, 0, 1, 0); [cube addSublayer:[self faceWithTransform:ct]]; //add cube face 3 ct = CATransform3DMakeTranslation(0, -50, 0); ct = CATransform3DRotate(ct, M_PI_2, 1, 0, 0); [cube addSublayer:[self faceWithTransform:ct]]; //add cube face 4 ct = CATransform3DMakeTranslation(0, 50, 0); ct = CATransform3DRotate(ct, -M_PI_2, 1, 0, 0); [cube addSublayer:[self faceWithTransform:ct]]; //add cube face 5 ct = CATransform3DMakeTranslation(-50, 0, 0); ct = CATransform3DRotate(ct, -M_PI_2, 0, 1, 0); [cube addSublayer:[self faceWithTransform:ct]]; //add cube face 6 ct = CATransform3DMakeTranslation(0, 0, -50); ct = CATransform3DRotate(ct, M_PI, 0, 1, 0); [cube addSublayer:[self faceWithTransform:ct]]; //center the cube layer within the container CGSize containerSize = self.view.bounds.size; cube.position = CGPointMake(containerSize.width / 2.0, containerSize.height / 2.0); //apply the transform and return cube.transform = transform; return cube; } CATransform3D pt = CATransform3DIdentity; pt.m34 = -1.0 / 500.0; self.view.layer.sublayerTransform = pt; //set up the transform for cube 1 and add it CATransform3D c1t = CATransform3DIdentity; c1t = CATransform3DTranslate(c1t, 0, -100, 0); CALayer *cube1 = [self cubeWithTransform:c1t]; [self.view.layer addSublayer:cube1]; CATransform3D c2t = CATransform3DIdentity; c2t = CATransform3DTranslate(c2t, 0, 100, 0); c2t = CATransform3DRotate(c2t, -M_PI_4, 1, 0, 0); c2t = CATransform3DRotate(c2t, -M_PI_4, 0, 1, 0); CALayer *cube2 = [self cubeWithTransform:c2t]; [self.view.layer addSublayer:cube2];
记得以前说过m34么？还有CATransform3D。这些东西平日里用的很少，不需要直接就能写出来，只需要知道功能即可，当用到的时候就去找，然后复制过来改改。如果以后从事跟这个有关的，相信熟能生巧，惯例，附上github下载地址：https://github.com/codeliu6572/CATransformLayer
