Would it be possible to use the render to texture to select an image to render to, then use normal OpenGL commands with custom textures to do your own rendering, then use your module again to switch back to drawing to the backbuffer?
You should be able to do this. When you call the SetBuffer with an image it stores what texture it was using.
Also what are the requirements for render to texture, does it rely on having a certain version of OpenGL or a certain extension?
It requires opengl 1.1 and it shouldnt need any certain extensions