我们什么时候应该使用CATransformLayer？ [英] When should we use CATransformLayer?

问题描述

我已经阅读了文档和一些示例，但是仍然无法理解何时确切使用 CATransformLayer 。正常的 CALayer 使 z = 0 平面上的所有内容变平，但这不是 CATransformLayer 也可以吗？数学上的解释将非常有帮助。

I have read the documentation and several examples, but still cannot understand when exactly to use a CATransformLayer. A normal CALayer flattens everything at the z = 0 plane, but isn't that what a CATransformLayer does too? A mathematical explanation would be very helpful.

推荐答案

要完全了解CALayer和CATransformLayer之间的区别，您应该阅读文章

To fully understand what are the differences between CALayer and CATransformLayer, you should read this article

这是最好的教程，解释了如何使用 CATransformLayer 。

It is the best tutorial which explains how to use CATransformLayer.

不过要简单地说，

考虑一个场景（ CAlayer实例），在该场景中我们在相同的X，Y坐标但具有不同的Z轴上创建4个平面，并将其添加为 subLayers 到场景。然后将场景旋转一定角度。

But to say briefly,
Consider a scene(CAlayer instance) where we create 4 planes at the same X, Y coordinates but with different Z and add it as subLayers to scene.And rotate the scene by some angle.

因此，我们可能希望它看起来像

< img src = https://i.stack.imgur.com/gT6CW.png alt =在此处输入图片描述>

So, we might expect it looks like,

但是看起来，

But instead it looks like,

这是由于CALayer无法管理3D镜头的深度稀疏且仅将场景展平到单个Z层。要更正该深度问题，我们使用 CATransformLayer ，它具有深度了解并基于此进行渲染。

This is due to the fact that a CALayer is incapable of managing the depth of a 3D hierarchy and it just flattens the scene to a single Z level. To correct that depth issue, we use CATransformLayer, it has depth understanding and renders based on it.

注意：图片摘自本文。

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