Unfortunately the demo-reel isn't yet available for public consumption, but over on Wired, you can find a very detailed article painstakingly describing everything they saw and learnt about Epic Games' Unreal Engine 4 in its debut press presentation.

As we've come to expect from these early tech-demos from Epic, the level of detail is another cut above anything that's out there right now. Running in real-time on one of Nvidia's new Kepler-architecture GeForce GTX 680s, the presentation showed an armour-clad demonic figure in a volcanic mountain-top fortress with liberal use of smoke, embers and liquid-hot-magma effects.

In previous engines, one floating ember was enough to slow performance considerably; a shower of them was impossible. With Unreal Engine 4, there can be millions of such particles, as long as the hardware is potent enough to sustain them. Game developers overuse features of every new engine, because they are suddenly so easy to implement. In the original Unreal Engine, for example, the ability to render colored lighting led to a rash of games that employed the effect. The same may prove true for UE4′s particle effects, for better or worse. (“Mark my words,” Bleszinski says, “those particles are going to be whored by developers.”)

In one 153-second clip, the Epic team has packed all the show-off effects that have flummoxed developers for years: lens flare, bokeh distortion, lava flow, environmental destruction, fire, and detail in landscapes many miles away. Plus, it’s breathtakingly photo-realistic—or would be if demon knights were, you know, a real thing.

Upon completion of the cinematic sequence, direct control was taken by the epic presenter to navigate around the world in a first person perspective:

Willard maneuvers his avatar into a dimly lit room where a flashlight turns on, revealing eddies of dust—thousands of floating particles that were invisible until exposed. In another room, globes of various sizes float in the air. Willard rolls a light-emanating orb along the floor (think of a spherical flashlight that rolls like a bowling ball) and beams of light wobble and change direction, illuminating parts of the room and revealing the clusters of floating spheres with a kind of strobe effect. At first it all seems perfectly familiar: “Well, yeah,” you think, “that’s how they’d act in the real world. What’s the big deal?” But it is a big deal: This is stuff that videogames have never been able to simulate—the effects simply aren’t possible on today’s consoles.

It's not all about visual fidelity either, as the Wired article goes on to describe the Kismet 2 visual scripting tool. Epic's Tim Sweeney explains that as the rendering tech evolves and improves, that it becomes more and more laborious for artists, animators and level designers to craft the content that takes advantage of it, so productivity increases in these processes at the engine-level are essential.

Need to determine how many bullets it will take to shatter that reinforced glass? Kismet 2 is your tool. Once behaviors are set, they can be executed immediately and edited on the fly. With Kismet 2, Epic empowers level designers—the people responsible for conceptualizing the world—to breathe life into that world directly, rather than relying on programmers to do it on their behalf. Says Golding, “We’re turning our level designers into godlike creatures who can walk into a world and create with a swipe of their hand.”

For more details and screenshots from the demo, check out the full Wired article. The public unveiling of this demo and more details about Unreal Engine 4 are expected in early June around the E3 expo.