Swift-CATransformLayer

CATransformLayer用来创建真是的3D层次视图，而不是像其他的CALayer通过扁平的层次结果去渲染视图模型.

不同于普通的CALayer中子图层的z轴是0， CATransformLayer的子图层Z轴不为0，因此有很大普通CALayer的特性CATransformLayer并不支持.

• 只有子图层被渲染，CALayer的很多特性被忽略，包括背景颜色，contents，边框设置，绘制样式属性等.

• 默认的二维图片的处理也被忽略，包括 filters, backgroundFilters, compositingFilter, mask, masksToBounds, and shadow style properties.

• 透明度属性只是作用于单独的图层，并不作用于整个图层组.

• hitTest方法永远都不会被调用，因为hitTest是基于二维坐标系无法映射到三维坐标系.

CATransformLayer与CALayer对比.png

效果图中的第一个图是通过CATransformLayer添加子视图的结果，第二个是CALayer添加自视图的结果，背景的Layer都设置了m34(景深)设置.

CATransformLayer代码:

        let layer = CATransformLayer()
        layer.addSublayer(layerOfColor(.red, zPosition: 20))
        layer.addSublayer(layerOfColor(.green, zPosition: 40))
        layer.addSublayer(layerOfColor(.orange, zPosition: 60))
        
        var perspective = CATransform3DIdentity
        perspective.m34 = -1 / 100
        layer.transform = CATransform3DRotate(perspective, 0.1, 0, 1, 0)
        layer.backgroundColor = UIColor.gray.cgColor
        self.view.layer.addSublayer(layer)

CALayer代码:

        let layer = CALayer()
        layer.addSublayer(layerOfColor(.red, zPosition: 20))
        layer.addSublayer(layerOfColor(.green, zPosition: 40))
        layer.addSublayer(layerOfColor(.orange, zPosition: 60))
        
        var perspective = CATransform3DIdentity
        perspective.m34 = -1 / 100
        layer.transform = CATransform3DRotate(perspective, 0.1, 0, 1, 0)
        layer.backgroundColor = UIColor.gray.cgColor
        layer.frame = CGRect(x: 0, y: 300, width: 300, height: 300)
        self.view.layer.addSublayer(layer)

    func layerOfColor(_ color: UIColor, zPosition: CGFloat) -> CALayer {
        let layer = CALayer()
        layer.frame = CGRect(x: 50, y: 50, width: 100, height: 100)
        layer.backgroundColor = color.cgColor
        layer.zPosition = zPosition
        layer.opacity = 0.5
        
        return layer
    }

参考资料:
https://developer.apple.com/documentation/quartzcore/catransformlayer