A huge day for gamers just hit as Epic and Mozilla (News – Alert) brought out the demo of Unreal Engine 3 for HTML5, and by all reports, the demo is absolutely spectacular. With some amazing benchmarks to its credit, the Unreal Engine 3 unveiling may be just the powerhouse that gamers were hoping for, and the kind of thing that developers can use to bring out some thoroughly amazing titles.

The engine was running as part of the Unreal Engine 3 Epic Citadel Demo, ported to WebGL, JavaScript and HTML5 alike by Unreal and Mozilla. Early tests of the engine—even on hardware that might be considered less than optimal; one test was described as running on a PC that was three years old—show some pretty impressive benchmarks, including a display resolution of 1920 x 1200, running at a whopping 138 frames per second.

The development process in getting Unreal Engine 3 to light was no less impressive than the benchmarks it generated. Reports from the recently-concluded Game Developer Conference suggested that porting Unreal Engine 3 to JavaScript and WebGL was a process that took just four days. While the coalition behind it then showed off the demo running within Firefox, it took around a month to make the move from show floor demo to publicly accessible demo.

The Epic Citadel demo itself is a fairly small affair, with 52 megabytes of JavaScript running the show and calling on WebGL to set up the graphics in HTML5. Visiting the site allows Mozilla’s new asm.js feature to download and run the relevant JavaScript to allow a browser to, essentially, download, compile, and execute Unreal Engine 3 right on the browser itself. This opens up an impressive array of new possibilities, and in the fairly short term as well.

There’s a little bit of bad news for those wanting to try this demo out for themselves, though: it’s only going to run on a browser that supports both HTML5 and WebGL, and one that has a sound JavaScript engine to boot. That limits the choices substantially to Chrome and Firefox Nightly, and reports indicate that even Chrome is having a tough time getting this one to work, with frequent crashes associated with the demo. However, the reports further suggest that fixes should be along soon to take care of that, so Chrome users should be able to get in on the action directly. Additionally, there’s a bit of a performance hit associated with running the program—some things just won’t be possible, at least for now—but many common applications should be ready to go.

This isn’t so much a big deal for what it is—though what it is is plenty impressive—so much as it is a big deal for what it could be down the line. Web apps have come a long way since the simplest days of Flash and the like, and the sheer progress has incredible implications. Even the current models are showing that Web browsers are capable of some absolutely amazing things, and may well generate whole new models of gaming, productivity, and other kinds of Web applications.

Today’s Web apps are opening up an absolutely dizzying scale of possibilities, and seeing just what that possibility turns into down the line should be positively breathtaking.