Originally Posted by AaronP
I talked to an OpenGL engineer about this and he explained that the FBO extension is not designed to be fast in the case that you modify a texture while its FBO is bound, and that binding and then unbinding the FBO around the ReadPixels loop eliminates the slowdown.
The drawpixels question still needs to be investigated.
I tried unbinding before the transference and binding back after the transference, even I have tried to unbind the texture from the COLOR_ATTACHMENT0 before unbinding the framebuffer object, but the transferences are still extremely slow with 9xxx drivers. I don't know what else I can try
Thanks for your help!
BTW: ReadPixels is quite fast (in both driver versions), it is glTexSubImage what is very slow.