User:Soumyasch/Incubator/DirectX

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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. DirectX, then, was the generic term for all of these Direct-something APIs, and that term became the name of the collection. After the introduction of the Xbox, Microsoft has also released multiplatform game development APIs such as XInput, which are designed to supplement or replace individual DirectX components.

Direct3D (the 3D graphics API within DirectX) is widely used in the development of computer games for Microsoft Windows, Microsoft Xbox, and Microsoft Xbox 360. Direct3D is also used by other software applications for visualization and graphics tasks, most notably among the engineering sector for CAD/CAM, because of its ability to quickly render high-quality 3D graphics using DirectX-compatible graphics hardware. 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 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. 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.

The latest versions of Direct3D, namely, Direct3D 10 and Direct3D 9Ex, are exclusive to Windows Vista. The reasons, as Microsoft claims, is that there were extensive changes in the Windows graphics architecture, and in particular the introduction of the Windows Display Driver Model. Critics argue that there may be possible commercial motives as well. This redesign of the graphics infrastructure for Windows Vista supports virtualizing graphics hardware to multiple applications and services such as the Desktop Window Manager, in contrast to the exclusive access afforded to DirectX applications on Windows XP. Both Direct3D 9Ex and Direct3D 10 rely on the WDDM infrastructure and WDDM drivers.

Components


The components comprising DirectX are
 * DirectX Graphics, which consists of several APIs:
 * DirectDraw: for drawing 2D Graphics (raster graphics).  Now deprecated, though still in use by a number of games.
 * Direct3D (D3D): for drawing 3D graphics.
 * DXGI: for enumerating adapters and monitors and managing swap chains for Direct3D 10 and up.
 * DirectInput: for interfacing with input devices including keyboards, mice, joysticks, or other game controllers.  Deprecated after version 8 in favor of XInput for Xbox360 controllers or standard WM INPUT window message processing for keyboard and mouse input.
 * DirectPlay: for communication over a local-area or wide-area network.  Deprecated after version 8.
 * DirectSound: for the playback and recording of waveform sounds.
 * DirectSound3D (DS3D): for the playback of 3D sounds.
 * DirectMusic: for playback of soundtracks authored in DirectMusic Producer.
 * DirectX Media: comprising DirectAnimation for 2D web animation, DirectShow for multimedia playback and streaming media, DirectX Transform for web interactivity, and Direct3D Retained Mode for higher level 3D graphics.  DirectShow contains DirectX plugins for audio signal processing and DirectX Video Acceleration for accelerated video playback.

''As of April 2005 DirectShow is no longer a part of the DirectX API. It now comes bundled along with the Platform SDK.''


 * DirectX Media Objects: support for streaming objects such as encoders, decoders, and effects.
 * DirectSetup: for the installation of DirectX components.  Not a game API per se.

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 9 and the XNA graphics library.

DirectX 10
See also: Direct3D 10, Direct3D and Vista, List of games with DirectX 10 support

A major update to DirectX API, DirectX 10 ships with and is only available with Windows Vista; previous versions of Windows are not able to run DirectX 10-exclusive applications. Changes for DirectX 10 were extensive, but only Direct3D featured a major overhaul of the API.

Many former parts of DirectX API were deprecated in the latest DirectX SDK and will be preserved for compatibility only: DirectInput was deprecated in favor of XInput, DirectSound was deprecated in favor of XACT and lost support for hardware accelerated audio, since Vista audio stack renders sound in software on the CPU. The DirectPlay DPLAY.DLL was also removed and was replaced with dplayx.dll; games that rely on this DLL must duplicate it and rename it to dplay.dll.

In order to achieve backwards compatibility, DirectX in Windows Vista contains several versions of Direct3D:


 * Direct3D 9: emulates Direct3D 9 behavior as it was on Windows XP. Details and advantages of Vista's Windows Display Driver Model are hidden from the application if WDDM drivers are installed.  This is the only API available if there are only XP graphic drivers (XPDM) installed, after an upgrade to Vista for example.
 * Direct3D 9Ex (known internally during Windows Vista development as 9.0L or 9.L, the L referring to Longhorn, the codename for Windows Vista): allows full access to the new capabilities of WDDM (if WDDM drivers are installed) while maintaining compatibility for existing Direct3D applications. The Windows Aero user interface relies on D3D 9Ex.
 * Direct3D 10: Designed around the new driver model in Windows Vista and featuring a number of improvements to rendering capabilities and flexibility, including Shader Model 4.

Direct3D 10.1 is an incremental update of Direct3D 10.0 which will be shipped with, and require, Windows Vista Service Pack 1 in February 2008. This release mainly sets a few more image quality standards for graphics vendors, while giving developers more control over image quality. It also requires a whole new set of requirements, including Shader Model 4.1 and 32-bit floating-point operations. Direct3D 10.1 still fully supports Direct3D 10 hardware, but to be able to support all the features you need a card with the required hardware. As of March 5, 2008, only the ATI Radeon HD3xxx series GPUs are compliant.

History
In late 1994 Microsoft was just on the verge of releasing its next operating system, Windows 95. The main factor that would determine the value consumers would place on their new operating system very much rested on what programs would be able to run on it. Three Microsoft employees &mdash; Craig Eisler, Alex St. John, and Eric Engstrom &mdash; 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.

DOS allowed direct access to video cards, keyboards and 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 way that would let programmers get what they wanted, and they needed it quickly; the operating system was only months away from being released. Eisler, St. John, and Engstrom worked together to fix this problem, with a solution that they eventually named DirectX.

The first version of DirectX released was shipped September of 1995 as the Windows Games SDK. It was the Win32 replacement for the DCI and WinG APIs for Windows 3.1. A development team at ATI brought fundamental game graphics technology to the attention of Microsoft. The development of DirectX was led by the team of Eisler (development lead), St. John, and Engstrom (program manager). Simply put, it 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.

Prior to DirectX's existence, Microsoft had already included OpenGL on their Windows NT platform. At the time, OpenGL required "high-end" hardware and was limited to engineering and CAD uses. Direct3D (introduced by Eisler, Engstrom, and St. John as an alternative to SGI's OpenGL) was intended to be a lightweight partner to the back then slower OpenGL for game use. As the power of graphics cards and the computers running them grew, OpenGL became the de-facto standard and a mainstream product. At that point a "battle" began between supporters of the cross-platform OpenGL and the Windows-only Direct3D, which many argued was another example of Microsoft's embrace, extend and extinguish business tactic (see Fahrenheit or Direct3D vs. OpenGL). Nevertheless, 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). However, the combination of OpenGL and SDL for this purpose is becoming increasingly popular.

In a console-specific version, DirectX was used as a basis for Microsoft's Xbox and Xbox 360 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 is 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.

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 is, however, still required to build the DirectShow samples.

Release history
Notes:


 * 1) DirectX 4 was never released.  Raymond Chen explained in his book, The Old New Thing, that after DirectX 3 was released, Microsoft began developing versions 4 and 5 at the same time.  Version 4 was to be a shorter-term release with small features, whereas version 5 would be a more substantial release.  The lack of interest from game developers in the features slated for DirectX 4 resulted in its being shelved, and the corpus of documents that already distinguished the two new versions resulted in Microsoft choosing to not re-use version 4 to describe features intended for version 5.
 * 2) The version number as reported by Microsoft's DxDiag tool (version 4.09.0000.0900 and higher) use the x.xx.xxxx.xxxx format for version numbers.  However, the DirectX and Windows XP MSDN page claims that the registry always has in the x.xx.xx.xxxx format.  Put another way, when the above table lists a version as '4.09.00.0904' the registry may have it as '4.09.0000.0904'.

History of DirectX logo
The logo originally resembled a deformed radiation warning symbol. Controversially, the original name for the DirectX project was the "Manhattan Project", a reference to the US nuclear weapons initiative and its ultimate outcome &mdash; the nuclear bombing of Japan. Alex St. John, the director of the DirectX project at its inception, claims that this connotation is intentional, and that DirectX and its sister project, the Xbox (which shares a similar logo), are meant to displace Japanese videogame makers from their dominance of the industry. However, this meaning is publicly denied by Microsoft, who instead claims that it is merely artistic design.

Awards and accolades
On January 8, 2007, DirectX (specifically, Direct3D) earned a Technology & Engineering Emmy Award for Microsoft and partners AMD and Nvidia Corporation "for pioneering work in near and real-time fully programmable shading via modern graphics processors."

Compatibility
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 only have 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 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. For example, a game designed for and running on Direct3D 9 with a graphics adapter driver designed for Direct3D 6 would still work, albeit possibly with gracefully degraded functionality. However, as of Windows Vista, due to the significantly updated DDI for Windows Display Driver Model drivers, Direct3D 10 cannot run on older hardware drivers.

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.

.NET Framework
In 2002 Microsoft released a version of DirectX compatible with the Microsoft .NET Framework, thus allowing programmers to take advantage of DirectX functionality from within .NET applications using compatible languages such as managed C++ or the use of the C# programming language. This API was known as "Managed DirectX" (or MDX for short), and claimed to operate at 98% of performance of the underlying native DirectX APIs. In December 2005, February 2006, April 2006, and August 2006, Microsoft released successive updates to this library, culminating in a beta version called Managed DirectX 2.0. While Managed DirectX 2.0 consolidated functionality that had previously been scattered over multiple assemblies into a single assembly, thus simplifying dependencies on it for software developers, development on this version has subsequently been discontinued, and it is no longer supported. The Managed DirectX 2.0 library expired on October 5th, 2006.

During the GDC 2006 Microsoft presented the XNA Framework, a new managed version of DirectX (similar but not identical to Managed DirectX) that is intended to assist development of games by making it easier to integrate DirectX, High Level Shader Language (HLSL) and other tools in one package. It also supports the execution of managed code on the Xbox 360. The XNA Game Studio Express RTM was made available on December 11 2006, as a free download for Windows XP. Unlike the DirectX runtime, Managed DirectX, XNA Framework or the Xbox 360 APIs (XInput, XACT etc) have not shipped as part of Windows. Developers are expected to redistribute the runtime components along with their games or applications.

No Microsoft product including the latest XNA releases provides DirectX 10 support for the .NET Framework.

Alternatives
There are alternatives to the DirectX family of APIs, some more complete than others. While there is no unified solution that will do everything DirectX does, with a combination of libraries &mdash; SDL, Allegro, OpenMAX, OpenML, OpenGL, OpenAL, FMOD, etc. &mdash; one can implement a comparable but cross-platform and frequently free/open source solution.

There are also alternative implementations that aim to provide the same API, such as the one in Wine.