DirectX

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. Microsoft employee Alex St. John had been in discussions with various game developers asking how likely they would be to bring their MS-DOS games to Windows 95, and found the responses mostly negative; programmers had found that the Windows environment did not provide the necessary features which were available under MS-DOS using BIOS routines or direct hardware access.[6] There were also strong fears of compatibility; a notable case of this was from Disney's Animated Storybook: The Lion King which was based on the WinG programming interface.[7] Due to numerous incompatible graphics drivers from new Compaq computers that were not tested with the WinG interface which came bundled with the game, it crashed so frequently on many desktop systems that parents had flooded Disney's call-in help lines.[8][9]

St. John recognized the resistances for game development under Windows would be a limitation, and recruited two additional engineers, Craig Eisler and Eric Engstrom, to develop a better solution to get more programmers to develop games for Windows. The project was codenamed the Manhattan Project, as in relation to the World War II project of the same name, the idea was to displace the Japanese-developed video game consoles with personal computers running Microsoft's operating system.[8] It had initially used the radiation symbol as its logo but Microsoft asked the team to change the logo.[8] Management did not agree to the project as they were already writing off Windows as a gaming platform, but the three committed towards this project's development.[9] Their rebellious nature led Brad Silverberg, the senior vice president of Microsoft's office products, to name the trio the "Beastie Boys".[10]

Most of the work by the three was done among other assigned projects starting near the end of 1994.[9] Within four months and with input from several hardware manufacturers, the team had developed the first set of application programming interfaces (APIs) which they presented at the 1995 Game Developers Conference.[9] The SDK included libraries implementing DirectDraw for bit-mapped graphics,[11] DirectSound for audio,[12] and DirectPlay for communication between players over a network.[13] Furthermore, an extended joystick API already present in Windows 95 was documented for the first time as DirectInput,[14] while a description of how to implement the immediate start of the installation procedure of a software title after inserting its CD-ROM, a feature called AutoPlay, was also part of the SDK.[15] The "Direct" part of the library was so named as these routines bypassed existing core Windows 95 routines and accessed the computer hardware only via a hardware abstraction layer (HAL).[16] Though the team had named it the "Game SDK" (software development kit), the name "DirectX" came from one journalist that had mocked the naming scheme of the various libraries. The team opted to continue to use that naming scheme and call the project DirectX.[8]

The first version of DirectX was released in September 1995 as the Windows Games SDK. Its DirectDraw component was the Win32 replacement for the DCI[17] and WinG APIs for Windows 3.1.[18] 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.[19]

To get more developers on board DirectX, Microsoft approached id Software's John Carmack and offered to port Doom and Doom 2 from MS-DOS to DirectX, free of charge, with id retaining all publishing rights to the game. Carmack agreed, and Microsoft's Gabe Newell led the porting project. The first game was released as Doom 95 in August 1996, the first published DirectX game. Microsoft promoted the game heavily with Bill Gates appearing in ads for the title.[8]

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.[20] It was at this event that Microsoft first introduced Direct3D, 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 added OpenGL to their Windows NT platform.[21] OpenGL had been designed as a cross-platform, window system independent software interface to graphics hardware by Silicon Graphics, Inc. to bring 3D graphics programming into the mainstream of application programming. Besides it could also be used for 2D graphics and imaging and was controlled by the Architectural Review Board (ARB) which included Microsoft.[22][23] Direct3D was intended to be a Microsoft controlled alternative to OpenGL, focused initially on game use. As 3D gaming grew game developers were discovering that OpenGL could be used effectively for game development.[24] At that point a "battle" began between supporters of the cross-platform OpenGL and the Windows-only Direct3D.[25] Incidentally, OpenGL was supported at Microsoft by the DirectX team. If a developer chose to use the OpenGL 3D graphics API in computer games, the other APIs of DirectX besides Direct3D were often combined with OpenGL 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, which 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.[26]

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.[27]

Real-time raytracing was announced as DXR in 2018. Support for compiling HLSL to SPIR-V was also added in the DirectX Shader Compiler the same year.[28]

DirectX is composed of multiple APIs:

• Direct3D (D3D): Real-time 3D rendering API
• DXGI: Enumerates adapters and monitors and manages swap chains for Direct3D 10 and later.
• Direct2D: 2D graphics API
• DirectWrite: Text rendering API
• DirectCompute: API for general-purpose computing on graphics processing units
• DirectX Diagnostics (DxDiag): A tool for diagnosing and generating reports on components related to DirectX, such as audio, video, and input drivers
• XACT3: High-level audio API
• XAudio2: Low-level audio API
• DirectX Raytracing (DXR): Real-time raytracing API
• DirectStorage: GPU-oriented file I/O API
• DirectML: GPU-accelerated machine learning and artificial intelligence API

Microsoft has deprecated the following components:

• DirectX Media: Consists of:
  • DirectAnimation for 2D/3D[31] web animation, DirectShow for multimedia playback and streaming media
  • DirectX Media Objects: Support for streaming objects such as encoders, decoders, and effects (Deprecated in favor of Media Foundation Transforms; MFTs)[32]
  • DirectX Transform for web interactivity, and Direct3D Retained Mode for higher level 3D graphics
  • DirectX plugins for audio signal processing
  • DirectX Video Acceleration for accelerated video playback (Deprecated in favor of Media Foundation)
• DirectDraw: 2D graphics API (Deprecated in favor of Direct2D)
• DirectInput: Input API for interfacing with keyboards, mice, joysticks, and game controllers (Deprecated after version 8 in favor of XInput for Xbox 360 controllers or standard WM_INPUT window message processing for keyboard and mouse input)
• DirectPlay: Network API for communication over a local-area or wide-area network (Deprecated after version 8 in favor of Games for Windows Live and Xbox Live)
• DirectSound: Audio API (Deprecated since DirectX 8 in favor of XAudio2 and XACT3)
• DirectSound3D (DS3D): 3D sounds API (Deprecated since DirectX 8 in favor of XAudio2 and XACT3)
• DirectMusic: Components for playing soundtracks authored in DirectMusic Producer (Deprecated since DirectX 8 in favor of XAudio2 and XACT3)

DirectX functionality is provided in the form of COM-style objects and interfaces. Additionally, while not DirectX components themselves, managed objects have been built on top of some parts of DirectX, such as Managed Direct3D[33] and the XNA graphics library[34] on top of Direct3D 9.

Microsoft distributes debugging tool for DirectX called "PIX".[35]

Various releases of Windows have included and supported various versions of DirectX, allowing newer versions of the operating system to continue running applications designed for earlier versions of DirectX until those versions can be gradually phased out in favor of newer APIs, drivers, and hardware.[97]

APIs such as Direct3D and DirectSound need to interact with hardware, and they do this through a device driver. Hardware manufacturers have to write these drivers for a particular DirectX version's device driver interface (or DDI), and test each individual piece of hardware to make them DirectX compatible. Some hardware devices have only DirectX compatible drivers (in other words, one must install DirectX in order to use that hardware). Early versions of DirectX included an up-to-date library of all of the DirectX compatible drivers currently available. This practice was stopped however, in favor of the web-based Windows Update driver-update system, which allowed users to download only the drivers relevant to their hardware, rather than the entire library.

Prior to DirectX 10, DirectX runtime was designed to be backward compatible with older drivers, meaning that newer versions of the APIs were designed to interoperate with older drivers written against a previous version's DDI. The application programmer had to query the available hardware capabilities using a complex system of "cap bits" each tied to a particular hardware feature. Direct3D 7 and earlier would work on any version of the DDI, Direct3D 8 requires a minimum DDI level of 6 and Direct3D 9 requires a minimum DDI level of 7.[98] However, the Direct3D 10 runtime in Windows Vista cannot run on older hardware drivers due to the significantly updated DDI, which requires a unified feature set and abandons the use of "cap bits".

Direct3D 10.1 introduces "feature levels" 10_0 and 10_1, which allow use of only the hardware features defined in the specified version of Direct3D API. Direct3D 11 adds level 11_0 and "10 Level 9" - a subset of the Direct3D 10 API designed to run on Direct3D 9 hardware, which has three feature levels (9_1, 9_2 and 9_3) grouped by common capabilities of "low", "med" and "high-end" video cards; the runtime directly uses Direct3D 9 DDI provided in all WDDM drivers. Feature level 11_1 has been introduced with Direct3D 11.1.

There are alternatives to the DirectX family of APIs, with OpenGL, its successor Vulkan, Metal and Mantle having the most features comparable to Direct3D. Examples of other APIs include SDL, Allegro, OpenMAX, OpenML, OpenAL, OpenCL, FMOD, SFML etc. Many of these libraries are cross-platform or have open codebases. There are also alternative implementations that aim to provide the same API, such as the one in Wine. Furthermore, the developers of ReactOS are trying to reimplement DirectX under the name "ReactX".

• DxDiag
• Direct3D
• Vulkan
• Simple DirectMedia Layer
• Comparison of OpenGL and Direct3D
• Graphics Device Interface (GDI)
• Graphics pipeline
• DirectX plugin
• ActiveX
• Timeout Detection and Recovery

• Microsoft's DirectX developer site
• DirectX at Curlie
• The State of DirectX 10 - Image Quality & Performance