First off, its water physics and lighting are vastly improved over the current model, offering "the most realistic virtual ocean you've ever seen," according to Assassin's Creed 4's associate producer Sylvain Trottier.
It also allows incredibly detailed weather effects, like individually lit raindrops and "dynamic ripple shaders." Lighting, too, has been given a makeover with its colour changing based on how it reflects of various materials, just like in real life.
Also notable is how much foliage the upcoming consoles can render at a time, so we don't get that awkward image of vegetation appearing before your very eyes several meters ahead as the world loads before you.
Will any of this make the game more fun to play? Probably not, but the jury's still out. But this will make it prettier to look at; and with a game featuring as superb art direction as Assassin's Creed 4, that counts for something. (Source eurogamer.net)