Square Enix had this to show at E3 to wow audiences with. It’s new tech, not necessarily a game, that this bit of footage shows off in realtime. In other words, none of this is pre-rendered.
Servers didn’t slave over hours to push out pixels frozen in film. Everything in this clip was happening, as the title says, in realtime until someone captured the demo to post on the ‘net. Which means that one day, possibly very soon, you might be playing a game that looks as good as this.