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Microsoft DirectX is a collection of application programming interfaces (APIs) for handling tasks related to multimedia, especially game programming and video, on Microsoft platforms. Originally, the names of these APIs all began with Direct, such as Direct3D, DirectDraw, DirectMusic, DirectPlay, DirectSound, and so forth. The name Direct''X'' was coined as shorthand term for all of these APIs (the X standing in for the particular API names) and soon became the name of the collection. When Microsoft later set out to develop a gaming console, the X was used as the basis of the name Xbox to indicate that the console was based on DirectX technology.〔(【引用サイトリンク】title=Microsoft: The meaning of Xbox - The Economist )〕 The X initial has been carried forward in the naming of APIs designed for the Xbox such as XInput and the Cross-platform Audio Creation Tool (XACT), while the DirectX pattern has been continued for Windows APIs such as Direct2D and DirectWrite. Direct3D (the 3D graphics API within DirectX) is widely used in the development of video games for Microsoft Windows, Sega Dreamcast, Microsoft Xbox, Microsoft Xbox 360, and Microsoft Xbox One. Direct3D is also used by other software applications for visualization and graphics tasks such as CAD/CAM engineering. As Direct3D is the most widely publicized component of DirectX, it is common to see the names "DirectX" and "Direct3D" used interchangeably. The DirectX software development kit (SDK) consists of runtime libraries in redistributable binary form, along with accompanying documentation and headers for use in coding. Originally, the runtimes were only installed by games or explicitly by the user. Windows 95 did not launch with DirectX, but DirectX was included with Windows 95 OEM Service Release 2.〔(【引用サイトリンク】title=DirectX Help )〕 Windows 98 and Windows NT 4.0 both shipped with DirectX, as has every version of Windows released since. The SDK is available as a free download. While the runtimes are proprietary, closed-source software, source code is provided for most of the SDK samples. Starting with the release of Windows 8 Developer Preview, DirectX SDK has been integrated into Windows SDK.〔(【引用サイトリンク】title=Where is the DirectX SDK? )〕 ==Development history== In late 1994, Microsoft was ready to release Windows 95, its next operating system. An important factor in the value consumers would place on it was the programs that would be able to run on it. Three Microsoft employees—Craig Eisler, Alex St. John, and Eric Engstrom—were concerned because programmers tended to see Microsoft's previous operating system, MS-DOS, as a better platform for game programming, meaning few games would be developed for Windows 95 and the operating system would not be as much of a success. This was compounded by negative reception surrounding the Windows port of ''The Lion King''. The game used WinG, which crashed on Compaq Presarios that came shipped with it following a partnership between Compaq and Disney, as the Cirrus Logic display drivers used by the Presarios were not thoroughly tested with the API. DOS allowed direct access to video cards, keyboards, mice, sound devices, and all other parts of the system, while Windows 95 - with its protected memory model - restricted access to all of these, working on a much more standardized model. Microsoft needed a quick solution for programmers; the operating system was only months away from being released. Eisler (development lead), St. John, and Engstrom (program manager) worked together to fix this problem, with a solution that they eventually named DirectX. The first version of DirectX was released in September 1995 as the Windows Games SDK. It was the Win32 replacement for the DCI〔(【引用サイトリンク】title=54 What is DCI? )〕 and WinG APIs for Windows 3.1. DirectX allowed all versions of Microsoft Windows, starting with Windows 95, to incorporate high-performance multimedia. Eisler wrote about the frenzy to build DirectX 1 through 5 in his blog.〔(Craig Eisler's blog post about the frenzy to build DirectX 1 through 5 ) on craig.theeislers.com〕 Initial adoption of DirectX by game developers was slow. There were fears that DirectX could be replaced as WinG had been, there was a performance penalty in using Windows over DOS, and there were many die-hard DOS programmers.〔 DirectX 2.0 became a component of Windows itself with the releases of Windows 95 OSR2 and Windows NT 4.0 in mid-1996. Since Windows 95 was itself still new and few games had been released for it, Microsoft engaged in heavy promotion of DirectX to developers who were generally distrustful of Microsoft's ability to build a gaming platform in Windows. Alex St. John, the evangelist for DirectX, staged an elaborate event at the 1996 Computer Game Developers Conference which game developer Jay Barnson described as a Roman theme, including real lions, togas, and something resembling an indoor carnival. It was at this event that Microsoft first introduced Direct3D and DirectPlay, and demonstrated multiplayer ''MechWarrior 2'' being played over the Internet. The DirectX team faced the challenging task of testing each DirectX release against an array of computer hardware and software. A variety of different graphics cards, audio cards, motherboards, CPUs, input devices, games, and other multimedia applications were tested with each beta and final release. The DirectX team also built and distributed tests that allowed the hardware industry to confirm that new hardware designs and driver releases would be compatible with DirectX. Prior to DirectX, Microsoft had included OpenGL on their Windows NT platform. At the time, OpenGL required "high-end" hardware and was focused on engineering and CAD uses. Direct3D was intended to be a lightweight partner to OpenGL, focused on game use. As 3D gaming grew, OpenGL developed to include better support for programming techniques for interactive multimedia applications like games, giving developers choice between using OpenGL or Direct3D as the 3D graphics API for their applications. At that point a "battle" began between supporters of the cross-platform OpenGL and the Windows-only Direct3D. Incidentally, OpenGL was supported at Microsoft by the DirectX team. If a developer chose to use OpenGL 3D graphics API, the other APIs of DirectX are often combined with OpenGL in computer games because OpenGL does not include all of DirectX's functionality (such as sound or joystick support). In a console-specific version, DirectX was used as a basis for Microsoft's Xbox, Xbox 360 and Xbox One console API. The API was developed jointly between Microsoft and Nvidia, who developed the custom graphics hardware used by the original Xbox. The Xbox API was similar to DirectX version 8.1, but is non-updateable like other console technologies. The Xbox was code named DirectXbox, but this was shortened to Xbox for its commercial name.〔J. Allard, (PC Pro Interview ), April 2004〕 In 2002, Microsoft released DirectX 9 with support for the use of much longer shader programs than before with pixel and vertex shader version 2.0. Microsoft has continued to update the DirectX suite since then, introducing Shader Model 3.0 in DirectX 9.0c, released in August 2004. As of April 2005, DirectShow was removed from DirectX and moved to the Microsoft Platform SDK instead. DirectX has been confirmed to be present in Microsoft's Windows Phone 8.〔(【引用サイトリンク】 title=Windows Phone 8 adds DirectX, native development, easier app porting )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「DirectX」の詳細全文を読む スポンサード リンク
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