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-The OpenGL Extension Wrangler Library- - - - -Automatic Code Generation- --Starting from release 1.1.0, the source code and parts of the -documentation are automatically generated from the extension -specifications in a two-step process. In the first step, -specification files from the OpenGL registry are downloaded and -parsed. Skeleton descriptors are created for each extension. These -descriptors contain all necessary information for creating the source -code and documentation in a simple and compact format, including the -name of the extension, url link to the specification, tokens, function -declarations, typedefs and struct definitions. In the second step, -the header files as well as the library and glewinfo source are -generated from the descriptor files. The code generation scripts are -located in the auto subdirectory. - - --The code generation scripts require GNU make, wget, and perl. On -Windows, the simplest way to get access to these tools is to install -Cygwin, but make sure that the -root directory is mounted in binary mode. The makefile in the -auto directory provides the following build targets: - - -
Adding a New Extension- --To add a new extension, create a descriptor file for the extension in -auto/core and rerun the code generation scripts by typing -make clean; make in the auto directory. - - --The format of the descriptor file is given below. Items in -brackets are optional. - - -
-<Extension Name> -Take a look at one of the files in auto/core for an -example. Note that typedefs and function signatures should not be -terminated with a semicolon. - - -Custom Code Generation--Starting from GLEW 1.3.0, it is possible to control which extensions -to include in the libarary by specifying a list in -auto/custom.txt. This is useful when you do not need all the -extensions and would like to reduce the size of the source files. -Type make clean; make custom in the auto directory -to rerun the scripts with the custom list of extensions. - - --For example, the following is the list of extensions needed to get GLEW and the -utilities to compile. - - -
-WGL_ARB_extensions_string Multiple Rendering Contexts (GLEW MX)- -Starting with release 1.2.0, thread-safe support for multiple -rendering contexts, possibly with different capabilities, is -available. Since this is not required by most users, it is not added -to the binary releases to maintain compatibility between different -versions. To include multi-context support, you have to do the -following: -
Note that according to the MSDN -WGL documentation, you have to initialize the entry points for -every rendering context that use pixel formats with different -capabilities For example, the pixel formats provided by the generic -software OpenGL implementation by Microsoft vs. the hardware -accelerated pixel formats have different capabilities. GLEW by -default ignores this requirement, and does not define per-context -entry points (you can however do this using the steps described -above). Assuming a global namespace for the entry points works in -most situations, because typically all hardware accelerated pixel -formats provide the same entry points and capabilities. This means -that unless you use the multi-context version of GLEW, you need to -call glewInit() only once in your program, or more precisely, -once per process. - -Separate Namespace- --To avoid name clashes when linking with libraries that include the -same symbols, extension entry points are declared in a separate -namespace (release 1.1.0 and up). This is achieved by aliasing OpenGL -function names to their GLEW equivalents. For instance, -glFancyFunction is simply an alias to -glewFancyFunction. The separate namespace does not effect -token and function pointer definitions. - - -Known Issues- --GLEW requires GLX 1.2 for compatibility with GLUT. - - - - |
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-The OpenGL Extension Wrangler Library- - - - -Initializing GLEW--First you need to create a valid OpenGL rendering context and call -glewInit() to initialize the extension entry points. If -glewInit() returns GLEW_OK, the initialization -succeeded and you can use the available extensions as well as core -OpenGL functionality. For example: - - -
-#include <GL/glew.h> Checking for Extensions- --Starting from GLEW 1.1.0, you can find out if a particular extension -is available on your platform by querying globally defined variables -of the form GLEW_{extension_name}: - - -
-if (GLEW_ARB_vertex_program) -In GLEW 1.0.x, a global structure was used for this task. To ensure -binary compatibility between releases, the struct was replaced with a -set of variables. - - --You can also check for core OpenGL functionality. For example, to -see if OpenGL 1.3 is supported, do the following: - - -
-if (GLEW_VERSION_1_3) -In general, you can check if GLEW_{extension_name} or -GLEW_VERSION_{version} is true or false. - - --It is also possible to perform extension checks from string -input. Starting from the 1.3.0 release, use glewIsSupported -to check if the required core or extension functionality is -available: - - -
-if (glewIsSupported("GL_VERSION_1_4 GL_ARB_point_sprite")) -For extensions only, glewGetExtension provides a slower alternative -(GLEW 1.0.x-1.2.x). Note that in the 1.3.0 release -glewGetExtension was replaced with -glewIsSupported. - - -
-if (glewGetExtension("GL_ARB_fragment_program")) Experimental Drivers- --GLEW obtains information on the supported extensions from the graphics -driver. Experimental or pre-release drivers, however, might not -report every available extension through the standard mechanism, in -which case GLEW will report it unsupported. To circumvent this -situation, the glewExperimental global switch can be turned -on by setting it to GL_TRUE before calling -glewInit(), which ensures that all extensions with valid -entry points will be exposed. - - -Platform Specific Extensions- --Platform specific extensions are separated into two header files: -wglew.h and glxew.h, which define the available -WGL and GLX extensions. To determine if a certain -extension is supported, query WGLEW_{extension name} or -GLXEW_{extension_name}. For example: - - -
-#include <GL/wglew.h> -Alternatively, use wglewIsSupported or -glxewIsSupported to check for extensions from a string: - - -
-if (wglewIsSupported("WGL_ARB_pbuffer")) Utilities- --GLEW provides two command-line utilities: one for creating a list of -available extensions and visuals; and another for verifying extension -entry points. - - -visualinfo: extensions and visuals- --visualinfo is an extended version of glxinfo. The -Windows version creates a file called visualinfo.txt, which -contains a list of available OpenGL, WGL, and GLU extensions as well -as a table of visuals aka. pixel formats. Pbuffer and MRT capable -visuals are also included. For additional usage information, type -visualinfo -h. - - -glewinfo: extension verification utility- --glewinfo allows you to verify the entry points for the -extensions supported on your platform. The Windows version -reports the results to a text file called glewinfo.txt. The -Unix version prints the results to stdout. - - -Windows usage: -- -glewinfo [-pf <id>] where <id> is the pixel format id for which the -capabilities are displayed. - -Unix usage: -- -glewinfo [-display <dpy>] [-visual <id>] where <dpy> is the X11 display and <id> is -the visual id for which the capabilities are displayed. - - - |
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-The OpenGL Extension Wrangler Library- - - - -Credits- --GLEW was developed by Milan -Ikits and Marcelo -Magallon. They also perform occasional maintainance to make sure -that GLEW stays in mint condition. Aaron Lefohn, Joe Kniss, and Chris -Wyman were the first users and also assisted with the design and -debugging process. The acronym GLEW originates from Aaron Lefohn. -Pasi Kärkkäinen identified and fixed several problems with -GLX and SDL. Nate Robins created the wglinfo utility, to -which modifications were made by Michael Wimmer. - - -Copyright- --GLEW is originally derived from the EXTGL project by Lev Povalahev. -The source code is licensed under the Modified BSD -License, the Mesa 3-D License (MIT -License), and the Khronos License (MIT -License). The automatic code generation scripts are released under -the GNU GPL. - - - |
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-The OpenGL Extension Wrangler Library- - - - -Supported GLX Extensions- -
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-The OpenGL Extension Wrangler Library- - - - --The OpenGL Extension Wrangler Library (GLEW) is a cross-platform -open-source C/C++ extension loading library. GLEW provides efficient -run-time mechanisms for determining which OpenGL extensions are -supported on the target platform. OpenGL core and extension -functionality is exposed in a single header file. GLEW has been -tested on a variety of operating systems, including Windows, Linux, -Mac OS X, FreeBSD, Irix, and Solaris. - - -Download Center--GLEW is distributed -as source and precompiled binaries. The latest release is -1.5.7 -[09-07-10]: - -- --
-An up-to-date copy is also available from the project -repository: - --svn co https://glew.svn.sourceforge.net/svnroot/glew/trunk/glew glew - - -Supported Extensions--The latest release contains support for OpenGL 3.3, OpenGL 4.1 and the following extensions: - - - -News-
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-The OpenGL Extension Wrangler Library- - - - -Installation- --To use the shared library version of GLEW, you need to copy the -headers and libraries into their destination directories. On Windows -this typically boils down to copying: - - -
- - --where {VC Root} is the Visual C++ root directory, typically -C:/Program Files/Microsoft Visual Studio/VC98 for Visual -Studio 6.0 or C:/Program Files/Microsoft Visual -Studio .NET 2003/Vc7/PlatformSDK for Visual Studio .NET. - - --On Unix, typing make install will attempt to install GLEW -into /usr/include/GL and /usr/lib. You can -customize the installation target via the GLEW_DEST -environment variable if you do not have write access to these -directories. - - -Building Your Project with GLEW--There are two ways to build your project with GLEW. - -Including the source files / project file--The simpler but less flexible way is to include glew.h and -glew.c into your project. On Windows, you also need to -define the GLEW_STATIC preprocessor token when building a -static library or executable, and the GLEW_BUILD preprocessor -token when building a dll. You also need to replace -<GL/gl.h> and <GL/glu.h> with -<glew.h> in your code and set the appropriate include -flag (-I) to tell the compiler where to look for it. For -example: - -
-#include <glew.h> -Depending on where you put glew.h you may also need to change -the include directives in glew.c. Note that if you are using -GLEW together with GLUT, you have to include glew.h first. -In addition, glew.h includes glu.h, so you do not -need to include it separately. - --On Windows, you also have the option of adding the supplied project -file glew_static.dsp to your workspace (solution) and compile -it together with your other projects. In this case you also need to -change the GLEW_BUILD preprocessor constant to -GLEW_STATIC when building a static library or executable, -otherwise you get build errors. - --Note that GLEW does not use the C -runtime library, so it does not matter which version (single-threaded, -multi-threaded or multi-threaded DLL) it is linked with (without -debugging information). It is, however, always a good idea to compile all -your projects including GLEW with the same C runtime settings. - - -Using GLEW as a shared library- --Alternatively, you can use the provided project files / makefile to -build a separate shared library you can link your projects with later. -In this case the best practice is to install glew.h, -glew32.lib, and glew32.dll / libGLEW.so to -where the OpenGL equivalents gl.h, opengl32.lib, and -opengl32.dll / libGL.so are located. Note that you -need administrative privileges to do this. If you do not have -administrator access and your system administrator will not do it for -you, you can install GLEW into your own lib and include subdirectories -and tell the compiler where to find it. Then you can just replace -<GL/gl.h> with <GL/glew.h> in your -program: - - -
-#include <GL/glew.h> -or: - - -
-#include <GL/glew.h> -Remember to link your project with glew32.lib, -glu32.lib, and opengl32.lib on Windows and -libGLEW.so, libGLU.so, and libGL.so on -Unix (-lGLEW -lGLU -lGL). - - --It is important to keep in mind that glew.h includes neither -windows.h nor gl.h. Also, GLEW will warn you by -issuing a preprocessor error in case you have included gl.h, -glext.h, or glATI.h before glew.h. - - - - |
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