If you play PC games, you have probably heard about something called DirectX. Upon completing installation of most new games, a dialogue box usually pops up that asks players if they'd like to upgrade to the latest version of DirectX. What this box doesn't tell you is what DirectX is, why you need it, and what perks (if any) the latest version might offer.

In simple terms, DirectX is the means by which many multimedia applications (including video games) interact with Microsoft Windows operating systems. In more technical terms, it's a set of low-level application programming interfaces -- commonly called APIs -- designed by Microsoft to facilitate activities related to the rendering of multimedia elements. The most well known of these APIs is Direct3D, which undertakes the formidable challenge of handling tasks related to the complex three-dimensional graphics found in modern games.

According to Microsoft's Phil Taylor, program manager for the software giant's in-house Aces game development studio, prior to DirectX developers "wrote directly to the metal," tech jargon for developing software for specific pieces of hardware. "DirectX represented a major improvement because it presented a standardized interface for programmers," he said.

It also meant that gamers would be able to install new components -- such as video cards and sound cards -- on their Windows computers secure in the knowledge that their games would still work under the new hardware configuration.

DirectX has become one of the major hubs around which the game industry revolves. NVIDIA public relations manager Ken Burns calls each major DirectX release a milestone for the industry. "It dictates what features will need to be supported in the graphics hardware, so that game developers can be assured that their newest features will be supported in the hardware," he explained. "The vast majority of games are built using DirectX and every graphics processing unit has to support it."

But DirectX is not alone. OpenGL, an API created by Silicon Graphics in 1992, was available four years before the first version of DirectX. OpenGL's newest iterations still work on Windows PCs, but its popularity on Microsoft platforms has withered over time. It's found a more receptive home on Macintosh computers and in the PlayStation3, leaving DirectX as the effective standard for the Windows PC gaming industry.

DirectX 10 and the advent of limitless special effects

DirectX was originally developed for Windows 95. New versions of the API have come either at the beginning or during the lifecycles of all Microsoft operating systems since. The release of the software giant's most recent operating system, Windows Vista, brought with it the tenth major update to DirectX, appropriately (if somewhat unimaginatively) dubbed DirectX 10.

With each new version of DirectX, programmers are provided more options and more resources with which to create ever more visually multifaceted games. DirectX 10 has been said to have provided the greatest leap forward yet in programming freedom offered by the API.

For example, DirectX 10 features a tool called Pixel Shader 4.0. An upgrade from Pixel Shaders available in previous versions of DirectX, Pixel Shader 4.0 is a program that modifies individual pixels by applying a variety of effects, such as shadows, textures, and lighting. Whereas previous versions of Pixel Shader restricted programmers to a set number of instructions on how to modify pixels, Pixel Shader 4.0 provides developers with the ability to code a virtually unlimited number of instructions to modify the appearance of pixels. (Though, in reality, the number of instructions will still be quite finite, since programmers must still take into account end users' hardware configurations and what they are capable of handling).

There are many other new features in DirectX 10 as well, including a geometry shader that works to create more realistic effects in areas such as motion blur, and support for video cards with a unified graphics processor architecture that let several types of shaders work together rather than separately, theoretically providing a noticeable boost in graphics performance.

The concepts at work become much more technical the deeper one digs into the technology. Suffice to say that, assuming it works as intended, DirectX 10 employs innovative performance efficiencies and provides new tools to programmers that will help make games look better.

Windows XP gamers shunned

But while DirectX 10 is meant to improve PC gaming, not all PC gamers are keen to adopt it. The loudest complaint heard from consumers is that it is compatible only with Windows Vista, which forces PC game lovers to migrate to Microsoft's new operating system in order to enjoy games with the latest, most innovative graphics.

According to Microsoft, DirectX 10's dependency on Vista was unavoidable. "DirectX 10 makes use of new features found only in Vista," explained Taylor, adding that it would necessarily lose many of its efficiencies and multimedia enhancements had it been designed to work on older operating systems. "Vista and DirectX 10 are effectively joined at the hip."

Of course, as many consumers have noted, Microsoft has an obvious stake in making people move to their new operating system. However, DirectX 10's link to Vista cannot be attributed to Microsoft alone.

According to NVIDIA's Burns, each new iteration of DirectX 10 is a collaborative effort between Microsoft and industry heavyweights. "Microsoft leads a graphics advisory board that includes members of NVIDIA, other independent hardware vendors, game developers, artists, and programmers," said Burns. "The board meets at various intervals to discuss which new graphics features are important to include in upcoming iterations of the DirectX API. We come together and map out what we expect to be the key 3D advances for the next few years."

In other words, Microsoft designs its API to handle existing and future technologies coming down the pipe from its industry partners, which means the game industry at large has a voice in each new iteration of DirectX, including their thoughts on operating system compatibility. DirectX 10 isn't compatible with earlier Windows operating systems because the industry as a whole is moving toward graphics functionality that is supported by Windows Vista and not Windows XP.

Vista: The inevitable future for PC gamers

The inescapable reality is that PC gamers will be forced, eventually, to upgrade to Windows Vista and DirectX 10 if they want to keep playing new games. At the moment, every game on the market that supports DirectX 10 also supports DirectX 9, but that won't always be the case.

Microsoft's Taylor projects that the first DirectX 10-only (and, hence, Windows Vista-only) games, "Will be available either by the end of this year or sometime in 2009."

NVIDIA's Burns agrees that DirectX 10-only compatibles are set to quickly multiply. He said more than 30 million DirectX 10 graphics processing units have already been sold, and that most new add-in cards on sale today are DirectX 10 compatible. "By 2009, nearly all PC games will offer DirectX 10 features," said Burns. Still, he noted that many consumers are still running hardware that only supports DirectX 9, which gives developers and publishers incentive to continue supporting the older API at least for the near future.

The big question, of course, is whether gamers have reason to look forward to their move to Vista and DirectX 10. According to Rahul Sood, head of HP's gaming division, they do. "It will take time for the mainstream to realize... that PC gaming is getting much better because Vista has enabled it," said Sood. "When Vista first came out the drivers weren't very good, there was no real benefit to DirectX 10, and some older games wouldn't work. But now there's better graphics and better sound effects as well as other performance features [that enhance PC games]."

In the end, the question isn't whether PC gamers should move to Windows Vista and DirectX 10, but rather when they should make the switch. That answer will vary from gamer to gamer and depend heavily on the upcoming crop of DirectX 10 compatible games, and whether they'll be playable on a Windows XP/DirectX 9 machine.

DirectX 9 vs. DirectX 10 Image Samples: