Sorry for the confusion.
I am using the code to do off-screen calculations. In this case I am adding two different images together each time. However, I want to do the next addition while still having access to the previous sum (texture). Therefore I need to create another texture and attach it to the FBO (dettaching the previous one but keeping the handle to it) so that the next addition can be run. The computation is run straight after the glFramebufferTexture2DEXT call.
Also, I realise I made an error in saying I called:
Quote:
glTexSubImage2D(GL_TEXTURE_RECTANGLE_NV, 0, 0, 0, width, height, ret.second, GL_FLOAT, data);
As this texture I have just created is the result of the calculation, it does not require any data as its data is about to be calculated.
I hope I've cleaned things up, if I'm still being stupid do tell!
Thanks all.