I'm working on a particle system using transform feedback, and I would like to know if it is possible to render to anything other than floats, like halfs, using Transform Feedback (OpenGL 3.3)? It would save some bytes and possibly speed up the process a little bit.
You can write unsigned integers and use bit manipulation to pack data into them into half of those integers.
You can use the ARB_shading_language_packing extension to help out in this process; it's pretty widely supported, even on older AMD HD3-5xxx cards (though I make no claim as to how well this actually works. They simply claim to support it).