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underthesun

using pixel shader for calculations..

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How does one go about getting the output from a fragment shader back into code (c++)? The method I know of consists of drawing then using glReadPixel or something along that line.. but last time I tried this, the performance wasn't so great.. Are FBOs what I'm looking for? Or is there something else that will let me get the output from the fragment shader? Thanks

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You could use FBO and attach whatever render target you like for the texture format. e.g. 32bit RGBA or 16 or 8 depending on your needs. Then bind that texture and use glGetTexImage or if you are using PBO you could use them also...

Remember the gl_FragColor will be gl_FragData[0], gl_FragData[1] depending on what attachment you are rendering to.

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Quote:
The method I know of consists of drawing then using glReadPixel or something along that line.. but last time I tried this, the performance wasn't so great..

There will always be some sort of overhead when you try reading data from the GPU, as they were designed for pumping pixels to the screen, not doing calculations for the CPU.

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