3D是在原来的基础上修改z轴，实现投影、拉伸等3D喜爱效果，iOS提供了一个3D变幻矩阵（CATtransform3D），通过这个矩阵可实现各种透视、拉伸、移动和缩放效果。
一、相关概念
1、锚点，其指定了bounds相对于position的值，同时也是变化时的中心点，默认为（0.5，0.5），
2、矩阵变化的原理，CATransform3D实质上是定义了一个三维变换,源码如下
public init(m11: CGFloat（x缩放）, m12: CGFloat(y切变), m13: CGFloat, m14: CGFloat, m21: CGFloat（x切变）, m22: CGFloat（y缩放）, m23: CGFloat, m24: CGFloat, m31: CGFloat, m32: CGFloat, m33: CGFloat, m34: CGFloat（透视）, m41: CGFloat（x平移）, m42: CGFloat（y平移）, m43: CGFloat（z平移）, m44: CGFloat)

二、3D动画效果
3D旋转效果：

override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        UIView.beginAnimations(nil, context: nil)
        UIView.setAnimationDuration(3)
       //旋转
        imgV!.layer.transform = CATransform3DMakeRotation(CGFloat(Double.pi/2), 1, 1, 1)
        //缩放
//        imgV!.layer.transform = CATransform3DMakeScale(0.1, 0.1, 0.1)
        //平移
//        imgV!.layer.transform = CATransform3DMakeTranslation(100, 100, 100)

        UIView.commitAnimations()
    }

三、Cover Flow 3D效果

F28129BF-D5FA-44C8-8008-19103FC186D7.png

import UIKit
class MyCoverFlowController: UIViewController {
    var imageViewArr:NSMutableArray?
    let imageV1:UIImageView = UIImageView(frame: CGRect(x: 100, y: 100, width: 200, height: 250))
    let imageV2:UIImageView = UIImageView(frame: CGRect(x: 100, y: 100, width: 200, height: 250))
    let imageV3:UIImageView = UIImageView(frame: CGRect(x: 100, y: 100, width: 200, height: 250))
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = UIColor.white
        imageViewArr = [imageV1,imageV2,imageV3];
        for i in 0...(imageViewArr?.count)!-1 {
            let imageV = imageViewArr?.object(at: i) as! UIImageView
            let path:String = "\((i+1)*1000)"
            imageV.image = UIImage(named: path)
            imageV.layer.anchorPoint.y = 0.0
            view.addSubview(imageV)
        }
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        for i in 0...(imageViewArr?.count)!-1 {
            var imageTransform:CATransform3D = CATransform3DIdentity
            imageTransform.m34 = -0.005;
            imageTransform = CATransform3DTranslate(imageTransform, 0.0, 150.0, 0.0)
            imageTransform = CATransform3DScale(imageTransform, 0.95, 0.6, 1.0)
            if i==0 {
                imageTransform = CATransform3DRotate(imageTransform, CGFloat(Double.pi/8), 0.0, 1.0, 0.0)
            }else if i==1 {
                imageTransform = CATransform3DRotate(imageTransform, CGFloat(-Double.pi/8), 0.0, 1.0, 0.0)
            }
            let imageView:UIImageView = imageViewArr?.object(at: i) as! UIImageView
            let animation = CABasicAnimation(keyPath: "transform")
            animation.fromValue = NSValue(caTransform3D: imageView.layer.transform)
            animation.toValue = NSValue(caTransform3D: imageTransform)
            animation.duration = 3
        /**************************/
            let ani:CABasicAnimation = CABasicAnimation()
            ani.keyPath = "position"
            ani.duration = 3
            if i==0{
                ani.toValue = NSValue(cgPoint: CGPoint(x: 100, y: 10))
            } else if i==1 {
                ani.toValue = NSValue(cgPoint: CGPoint(x: 300, y: 10))
            } else {
                ani.toValue = NSValue(cgPoint: CGPoint(x: 200, y: 20))
            }
            let anG:CAAnimationGroup = CAAnimationGroup()
            anG.duration = 3
            anG.repeatCount = 1
            anG.isRemovedOnCompletion = false
            anG.fillMode = CAMediaTimingFillMode.forwards
            anG.timingFunction = CAMediaTimingFunction(name: CAMediaTimingFunctionName.easeInEaseOut)
            anG.animations = [animation,ani]
            imageView.layer.add(anG, forKey: "\(i)")
        }
    }
}