Nope, transform feedback wasn't what I wanted. In the end, I ended up just rendering my opaque fragments to textures via Framebuffer, as normal, and rendering the transparent fragments to an SSBO using AMD's OIT linked list idea. Works pretty well, I think, even if I need a separate pass for sorting the transparent fragments? Now I'm making my lighting shaders make use of all this. Going pretty well, even if I need to defer some of my deferred lighting to another deferred lighting shader. :/