如何在iOS上使用OpenGL ES实现多层绘图？ [英] How to achieve multi-layered drawing with OpenGL ES on iOS?

问题描述

我想很快为iOS制作一个简单的绘图应用程序，但我无法完成绘图工作 - 好吧，保存每个图层上的内容并恢复图层。看起来所有图层都保存相同的像素。

I wanted to very quickly to make a simple drawing app for iOS, but I can't quite get the drawing to work - well, to save the content on each layer and restore the layers. It appears like all layers save the same pixels..

这个想法是有三层，并使用OpenGL ES在每一层上绘制。由于没有这方面的经验，我只是平铺了三个UIViews，并为每个UIView（教程中的PaintingView的修改版本）添加了一个OpenGL绘图画布。当用户交换绘图层时，我只是禁用了其他图层上的用户交互。

The idea was to have three layers and use OpenGL ES to draw on each layer. With no experience in the matter, I just tiled three UIViews and added a OpenGL drawing canvas to each UIView (a modified version of the PaintingView from the tutorial). When the user swapped drawing layer, I simply disabled user interaction on the other layers.

通过这种方法，我经历了很多奇怪的事情，我认为这些怪异源于我的方法。所以现在，我认为我应该以相同的方式在同一个PaintingView中制作三个全屏缓冲区，并且只需在它们之间进行OpenGL切换。

With this approach I experience a lot of oddities that I assume stems from my approach. So now, I think that I should somehow make three full screen buffers in the same PaintingView and just have OpenGL switch between them.

我能做些什么吗？有人有办法吗？

Am I on to something? Have anyone an approach that works?

任何关于主题的内容都可能有所帮助。谢谢。

Anything on-topic might help. Thanks.

推荐答案

您可以制作两个不同的帧缓冲区：一个用于绘制到屏幕，另一个用于绘制到纹理。
然后，您可以制作3种不同的纹理，它们将是您的图层。吸引他们。
最后，你可以将你拥有的纹理绘制到第一个帧缓冲区并显示在屏幕上。

You can make two different framebuffers: one for drawing to screen and second for drawing to texture. Then, you can make 3 different textures, they will be your layers. Draw to them. Finally, you can draw the textures you have to the first framebuffer and present in on screen.

你的绘制周期将是这样的：

Your draw cycle will be smth like this:

• bind RenderToTextureFramebuffer


• 将texture1附加到RenderToTextureFramebuffer


• 画出你的内容希望在第1层


• 将texture2附加到RenderToTextureFramebuffer


• 在第2层中绘制所需内容


• 附加texture3 to RenderToTextureFramebuffer


• 在第3层中绘制你想要的东西


• bind RenderToScreenFramebuffer


• bind texture1


• 绘制texture1（你的layer1）


• 绑定texture2


• 绘制texture2（你的layer2）


• 绑定texture3


• 绘制texture3（你的layer3）


• 在屏幕上显示最终图片

• bind RenderToTextureFramebuffer
• attach texture1 to RenderToTextureFramebuffer
• draw what you want in layer 1
• attach texture2 to RenderToTextureFramebuffer
• draw what you want in layer 2
• attach texture3 to RenderToTextureFramebuffer
• draw what you want in layer 3
• bind RenderToScreenFramebuffer
• bind texture1
• draw texture1 (your layer1)
• bind texture2
• draw texture2 (your layer2)
• bind texture3
• draw texture3 (your layer3)
• present final picture on screen

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