unity-1Unity Technologies has raised $5.5 million to finance its business of making 3-D game platforms for browser-based games, VentureBeat has learned.

The money came from Sequoia Capital. The San Francisco-based company has gained a lot of traction for its Unity 3D engine, which lets game developers create fast-action 3-D games that run inside a web browser.

Once gamers download a small Unity plug-in for a game, they can play any Unity-based game through a web browser. There is no need to download a big file to play the game itself. And while most browser-based games built with Adobe Flash are relatively slow and two-dimensional, Unity supports pretty high-quality 3-D graphics (see images built with Unity 3D).

unity-2You can still get better 3-D graphics from disk-based games or those that come with huge file downloads. But in the U.S. in particular, where broadband speeds are particularly low, many users give up on downloads before they finish. That explains why a lot of game makers, from Nickelodeon to Electronic Arts, have turned to Unity.

Unity has a limited time to capitalize on its advantage. There are other rival game engines out there, but the bigger threat is browser makers, who plan to include support for 3-D graphics in their browsers at some point.

Earlier this year, Unity launched a version of its engine for the iPhone. To date, more than 250 games are using the Unity engine to power their 3-D iPhone games.

Unity is expected to announce the financing next week at its Unite 2009 conference in San Francisco.