A Unigine developer discussed his team’s exploration into GI techniques, finding all current solutions to be insufficient, and created a new technique called SSRTGI. Similar to how SSR uses the G-buffer to generate accurate reflections in screenspace, this technique uses the G-buffer data to generate accurate global illumination in screenspace! It takes 1.3 ms to render in full HD (1920 x 1080) at medium settings on a GTX 1070, but it is fully dynamic: nothing in the scene has to be baked. And it is possible to combine it with baked objects.
This is a solution that is extremely flexible. And while, like all dynamic GI methods, it does require a bit more heft to render well, this is a solution that is future-proof: better settings will give you better results, it doesn’t require any special setup, and it seems to be capable of taking light from any direction. I’m guesstimating it would be possible to get this effect to work on the Xbox One X for less than 2ms for a full HD scene.
https://unigine.com/images/showcases/ssrtgi_final_on_off.gif