How do I create a downscaled copy of an FBO in OpenGL?

Posted by Jasper Bekkers on Stack Overflow See other posts from Stack Overflow or by Jasper Bekkers
Published on 2010-05-19T23:57:49Z Indexed on 2010/05/20 0:00 UTC
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opengl

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fbo

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ping-pong

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textures

Hi,

In order to speed up some post-processing shaders I'm using, I need to perform these operations on a framebuffer that is smaller in size than the actual window (about 1/4th or more). Most of the effects I want to optimize are simple blurring operations that could be replaced (for a large part) by smaller kernel and bilinear filtering. Thus, I need to create a copy of the current FBO into another one. However, I couldn't find anything, that works, on how to do this.

I've tried using glBlitframebufferEXT and rendering a fullscreen quad into the other framebuffer, but both paths result in a black texture as output. How do I go about solving this problem?

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