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.

But that's just the opening scene. After the cinematic, Epic's senior technical artist, Alan Willard, starts playing the demo. At this point the view switches to that disembodied first-person perspective made so ubiquitous by shooting games like the Call of Duty franchise and Epic's own influential Unreal titles. 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.