问题描述
我试图了解后处理的工作原理.
I'm trying to understand how post processing work.
根据我的理解，我需要做类似的事情:
From what I understood, I need to to something like that:
-> Bind render texture
-> Draw my scene
-> Unbind render texture
-> Draw a quad full screen using the resulting texture using a shader to apply an effect (blur, …)
该系统的问题是:如何在生成的四边形上应用多种效果?
The problem with that system is: How can I apply multiple effects on the resulting quad?
在我看来，我认为在最终的纹理上应用效果"(着色器)，然后绘制四边形可能是最好的解决方案，但是我不知道是否可能.
In my mind, I think applying the "effects" (shaders) on the resulting texture then drawing the quad his probably the best solution, but I don't know if it is possible.
我可以直接在材质上应用着色器吗?
Can I apply shaders on texture directly?
PS:这是我目前所做的，我现在可以在纹理中绘制所有场景:
PS: Here is what I've done for the moment, I can draw all my scene in a texture currently:
EffectManager(创建输出纹理并使用方法"add(PostEffect *)"
EffectManager (create the output texture and have a method "add(PostEffect*)"
推荐答案
我不知道将直接"着色器直接应用于"纹理的含义，但是要渲染具有特殊效果的纹理，则需要渲染全屏使用所需的着色器将其四分之一到屏幕，然后将纹理馈入着色器中.要产生多种效果，您需要使用两个帧缓冲区(ping响应)，如下所示:
I don't know what you mean with "directly applying" shaders to a texture, but to render a texture with a special effect you need to render a fullscreen quad to the screen with the shader you need, and of course feed the texture into the shader. To have multiple effects you need to use two framebuffers (ping-ponging), like this:
-> Bind 1st render texture
-> Draw scene
-> Bind 2nd render texture
-> Feed 1st render texture to a shader and draw quad
-> Bind 1st render texture
-> Feed 2nd render texture to another shader and draw quad
-> Bind 2nd render texture
-> Feed 1st render texture to a third shader and draw quad
...
-> Unbind
-> Draw quad
您不能在同一帧缓冲区中连续渲染两次，这就是为什么您需要这样做(请参见 https://www.opengl.org/wiki/Framebuffer_Object#Feedback_Loops ).
You cannot render two times in a row to the same framebuffer, which is why you need to do this way (see https://www.opengl.org/wiki/Framebuffer_Object#Feedback_Loops).
如果可以的话，请尝试将尽可能多的效果打包到同一着色器中，以最大程度减少喂入制服和绘图时的开销.
If you can, try to pack as many effects as possible into the same shader to minimize overhead when feeding uniforms and drawing.
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