who is it?
OpenGL (English:
Open Graphics Library
, Translation: Open Graphics Library or "Open Graphics Library") is used to render 2D, 3D vector graphics of cross-language, cross-platform application programming interface (API). This interface consists of nearly 350 different function calls composition, from simple to complex graphic bit rendering three-dimensional scene. While another program interface system is used only for Direct3D on Microsoft Windows. OpenGL commonly used in CAD, virtual reality, scientific visualization programs and video game development.
Efficient implementation of OpenGL (use of graphics acceleration hardware) exist for Windows, UNIX platforms and part of Mac OS. These implementations are typically provided by a display device manufacturer, and very dependent on the hardware manufacturer. Open source library Mesa is a pure software-based graphics API, which is code-compatible to OpenGL. However, for licensing reasons, it only claims to be a "very similar" API.
It features?
The OpenGL API defines several function may be called a client, and a number of named integer constant (e.g., constant GL_TEXTURE_2D decimal integer corresponding to 3553). Although similar to the C programming language function defined on surfaces, they are language-independent. Therefore, OpenGL there are many language bindings, it is worth mentioning include: JavaScript binding WebGL (based API OpenGL ES 2.0 in the Web browser 3D rendering); C bindings WGL, GLX and CGL; iOS offer the C bindings; Android provides Java and C bindings.
OpenGL is not only independent of language, and platform-independent. Specification acquisition and management OpenGL context mention relevant content, but these details as to the underlying window system. For the same reason, OpenGL purely focused on rendering, without providing input, audio and associated API window.
OpenGL is an evolving API. The new OpenGL specification will be published periodically by the Khronos Group, the new version to support a variety of new capabilities by extending the API. Each version of the details of the unanimous decision by the members of the Khronos Group, including the graphics card manufacturers, system designers and general operating technology companies similar to Mozilla and Google.
History?
In the 1980s, the development can be used in a wide variety of graphics hardware software is a real challenge. Typically, software developers write custom interfaces and drivers for each hardware. But this is very expensive and would lead to duplication of a lot of work.
The early 1990s, SGI has become a leader in the field of 3D graphics workstations. IRISGL of its API is considered the most advanced technology and become the de facto industry standard, open standards-based PHIGS dwarfs. IRIS GL easier to use, but also support rendering real-time mode. In contrast, PHIGS difficult to use and features old.
SGI's competitors (including Sun, HP and IBM) by extending the standard PHIGS 3D hardware can be put into the market. This in turn lead to the weakening of SGI market share, as more and more 3D graphics hardware suppliers to enter the market. To capture the market, SGI decided to IRIS GL API into an open standard, OpenGL.
However, SGI has a large number of software customers, for them to migrate from IRIS GL OpenGL will require huge investments. In addition, IRIS GL application programming interface has a function not related to 3D graphics. For example, it includes a window, the API keyboard and a mouse, which is partly due to the X Window System developed before and Sun's NeWS system. Moreover, IRIS GL library due to licensing and patent issues are not suitable open. All these factors continue to support the advanced requirements of SGI and proprietary IRIS Inventor and IRIS Performer API.
One of the limitations IRIS GL is only accessible by the underlying hardware supports. If the graphics hardware does not support a feature, then the application will not use it. OpenGL provide software support to overcome this problem by providing the hardware does not have the function, which allows applications to use advanced graphics technology in a relatively weak system. OpenGL standardized access to hardware way: the development of hardware interface programs (also sometimes called device drivers) handed over to hardware manufacturers, and window function entrusted to the underlying operating system. So that a large number of different types of graphics hardware speak the same language far-reaching impact, providing a higher level of 3D software development platform that software developers.
1992, SGI led the company to create OpenGL Architecture Review Board (OpenGL ARB) is. The committee consists of several companies responsible for future OpenGL standard to maintain and extend.
Microsoft released Direct3D in 1995, Direct 3D eventually become the main competitor of OpenGL. December 17, 1997, Microsoft and SGI initiated the Fahrenheit scale projects designed to unify OpenGL and Direct3D interfaces. In 1998, Hewlett-Packard added. Later, due to financial constraints at SGI, Microsoft's strategy and general lack of industry support, the project was abandoned in 1999.
In July 2006, OpenGL Architecture Review Board voted to OpenGL API standard control to the Khronos Group.
to sum up:
OpenGL is a prime tool for image rendering workers.