Hello all,
Question Probably asked before 
What is the most efficent way to render to an offscreen memory in order to use it later as a texture?
What are the extensions needed?
Many thanks,
Yossi
The most efficient metod is using EXT_framebuffer_object extension, but its quite new and no vendor have full support for it.
The second way is to render to pbuffer and use WGL_ARB_render_texture extension or just Pbuffer and copy the image to texture.