hello, In the recent discution on this list regarding gem an shader, i read that shader could not be used with framebuffer. i did not realize when i read this (and i can't find it anymore on the archieve). in fact it is not true. shader has to be loaded before the framebuffer objet but it work.
here is an exemple of how to use a shader and render on the framebuffer and then using the framebuffer as a texture send to an other shader.
hope that help
Cyrille