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GLEW: The OpenGL Extension Wrangler Library
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< td align = center > < font size = "+2" > < b > The OpenGL Extension Wrangler Library< / b > < / font > < / td >
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< tr > < td align = center > < a href = "#Introduction" > < font size = "-1" > Introduction< / font > < / a > < / td > < / tr >
< tr > < td align = center > < a href = "#Download" > < font size = "-1" > Obtaining GLEW< / font > < / a > < / td > < / tr >
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< tr > < td align = center > < a href = "#Supported" > < font size = "-1" > Supported Extensions< / font > < / a > < / td > < / tr >
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< tr > < td align = center > < a href = "#Build" > < font size = "-1" > How to Build Your Project with GLEW< / font > < / a > < / td > < / tr >
< tr > < td align = center > < a href = "#Install" > < font size = "-1" > How to Install GLEW< / font > < / a > < / td > < / tr >
< tr > < td align = center > < a href = "#Use" > < font size = "-1" > How to Use GLEW< / font > < / a > < / td > < / tr >
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< tr > < td align = center > < a href = "#Utilities" > < font size = "-1" > Utilities< / font > < / a > < / td > < / tr >
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< tr > < td align = center > < a href = "#Issues" > < font size = "-1" > Known Issues< / font > < / a > < / td > < / tr >
< tr > < td align = center > < a href = "#Credits" > < font size = "-1" > Credits, Copyright< / font > < / a > < / td > < / tr >
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< td bgcolor = "#FFF0D0" align = "center" > < a
name="Introduction">< font size = "+1" > < b > Introduction< / b > < / font > < / a >
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The goal of the OpenGL Extension Wrangler Library (GLEW) is to assist
C/C++ OpenGL developers with two tedious tasks: initializing and
using extensions and writing portable applications. GLEW provides
an efficient run-time mechanism to determine whether a certain
extension is supported by the driver or not. OpenGL core and
extension functionality is exposed via a single header file. GLEW
currently supports the products of two commodity graphics card
vendors, NVIDIA and ATI, on two operating systems, Windows and Linux.
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< td bgcolor = "#FFF0D0" align = "center" > < a
name="Download">< font size = "+1" > < b > Obtaining GLEW< / b > < / font > < / a >
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The source and precompiled binaries are available at the < a
href="http://glew.sourceforge.net/">project website< / a > .
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< td bgcolor = "#FFF0D0" align = "center" > < a
name="Supported">< font size = "+1" > < b > Supported Extensions< / b > < / font > < / a >
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< td > GLEW currently supports < a href = "glew.html" > OpenGL< / a > ,
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< a href = "wglew.html" > WGL< / a > , and < a href = "glxew.html" > GLX< / a >
extensions.
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< td bgcolor = "#FFF0D0" align = "center" > < a
name="Build">< font size = "+1" > < b > How to Build Your Project with GLEW< / b > < / font > < / a >
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There are two ways to build your project with GLEW.
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< font size = "+1" > < b > Including the source files / project file< / b > < / font >
< p >
The simpler but less flexible way is to include < tt > glew.h< / tt > and
< tt > glew.c< / tt > into your project and define the < tt > GLEW_STATIC< / tt >
preprocessor constant for the static library or executable you are
building together with GLEW. You also need to replace
< tt > < GL/gl.h> < / tt > and < tt > < GL/glu.h> < / tt > with
< tt > < glew.h> < / tt > and set the appropriate include flag
(< tt > -I< / tt > ) to tell the compiler where to look for it.
For example:
< blockquote > < pre > #include < glew.h>
#include < GL/glut.h>
< gl, glu, and glut functionality is available here>
< / pre > < / blockquote >
Note that if you are using GLEW together with GLUT, you have to
include < tt > glew.h< / tt > first. In addition, < tt > glew.h< / tt > includes
< tt > glu.h< / tt > , so you don't need to include it separately.
< p >
On Windows you can also add the supplied project file
(< tt > glew.dsp< / tt > or < tt > glew.vcproj< / tt > ) to your workspace or
solution and compile it together with your other projects. In this
case you need to change the < tt > GLEW_BUILD< / tt > preprocessor constant
to < tt > GLEW_STATIC< / tt > , otherwise you get build errors. < b > 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< / b > .
< p >
< font size = "+1" > < b > Using GLEW as a shared library< / b > < / font >
< p >
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 < tt > glew.h< / tt > ,
< tt > glew32.lib< / tt > , and < tt > glew32.dll< / tt > / < tt > libGLEW.so< / tt > to
where the OpenGL equivalents < tt > gl.h< / tt > , < tt > opengl32.lib< / tt > , and
< tt > opengl32.dll< / tt > / < tt > libGL.so< / tt > 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
< tt > < GL/gl.h> < / tt > with < tt > < GL/glew.h> < / tt > in your
program:
< blockquote > < pre > #include < GL/glew.h>
#include < GL/glut.h>
< gl, glu, and glut functionality is available here>
< / pre > < / blockquote >
or:
< blockquote > < pre > #include < GL/glew.h>
< gl and glu functionality is available here>
< / pre > < / blockquote >
< p >
Don't forget to link your project with < tt > glew32.lib< / tt > ,
< tt > glu32.lib< / tt > , and < tt > opengl32.lib< / tt > on Windows and
< tt > libGLEW.so< / tt > , < tt > libGLU.so< / tt > , and < tt > libGL.so< / tt > on
Linux (< tt > -lGLEW -lGLU -lGL< / tt > ).
< p >
It is important to keep in mind that < tt > glew.h< / tt > includes neither
< tt > windows.h< / tt > nor < tt > gl.h< / tt > . Also, GLEW will warn you by
issuing a preprocessor error in case you have included < tt > gl.h< / tt > ,
< tt > glext.h< / tt > , or < tt > glATI.h< / tt > before < tt > glew.h< / tt > .
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name="Install">< font size = "+1" > < b > How to Install GLEW< / b > < / font > < / a >
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To install the shared library version of GLEW you need to copy the
headers and libraries into their destination directories. On Windows
this boils down to copying (no, we will not write a Windows installer
for you).
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< tr > < td > < tt > lib/glew32.dll< / tt > < / td > < td > to < / td >
< td > < tt > %SystemRoot%/system32< / tt > , usually < tt > C:/WINDOWS/system32< / tt > < / td > < / tr >
< tr > < td > < tt > lib/glew32.lib< / tt > < / td > < td > to < / td >
< td > < tt > {VC Root}/Lib< / tt > < / td > < / tr >
< tr > < td > < tt > include/GL/glew.h< / tt > < / td > < td > to < / td >
< td > < tt > {VC Root}/Include/GL< / tt > < / td > < / tr >
< tr > < td > < tt > include/GL/wglew.h< / tt > < / td > < td > to < / td >
< td > < tt > {VC Root}/Include/GL< / tt > < / td > < / tr >
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where < tt > {VC Root}< / tt > is your Visual C++ directory, typically
< tt > C:/Program Files/Microsoft Visual Studio/VC98< / tt > for Visual
Studio 6.0 or < tt > C:/Program Files/Microsoft Visual
Studio/Vc7/PlatformSDK< / tt > for Visual Studio .NET. < b > However, if you
build GLEW with Visual Studio .NET, the project file will
automatically install it into these directories, so you
don't have to worry about installation at all< / b > .
< p >
On Linux, typing < tt > "make install"< / tt > will attempt to install GLEW
into < tt > /usr/include/GL< / tt > and < tt > /usr/lib< / tt > . You can
customize the installation target via the < tt > GLEW_TARGET< / tt >
environment variable if you do not have write access
to these directories.
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< td bgcolor = "#FFF0D0" align = "center" > < a
name="Use">< font size = "+1" > < b > How to Use GLEW< / b > < / font > < / a >
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< font size = "+1" > < b > Initializing GLEW< / b > < / font >
< p >
First you need to create a valid OpenGL rendering context and call
< tt > glewInit()< / tt > to initialize the extension entry points. If
< tt > glewInit()< / tt > returns < tt > GLEW_OK< / tt > the initialization
succeeded and you can use the available extensions as well as core
OpenGL functionality. For example:
< blockquote > < pre > #include < GL/glew.h>
#include < GL/glut.h>
...
glutInit(& argc, argv);
glutCreateWindow("GLEW Test");
int err = glewInit();
if (GLEW_OK != err)
{
/* problem: glewInit failed, something is seriously wrong */
fprintf(stderr, "Error: %s\n", glewGetErrorString(err));
...
}
< / pre > < / blockquote >
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< font size = "+1" > < b > Querying the available OpenGL extensions< / b > < / font >
< p >
To find out if a particular extension is available on your
platform, use the globally defined structure < tt > glew< / tt > :
< blockquote > < pre > if (glew.ARB_vertex_program)
{
/* it is safe to use the ARB_vertex_program extension here */
glGenProgramsARB(...);
}
< / pre > < / blockquote >
You can also check for core OpenGL functionality. For example, to
see if OpenGL 1.3 is supported you can use the following:
< blockquote > < pre > if (glew.GL_13)
{
/* Yay! OpenGL 1.3 is supported! */
}
< / pre > < / blockquote >
In general, you can check if < tt > glew.{extension_name}< / tt > or
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< tt > glew.GL_{version}< / tt > is set or not. For extensions
< tt > glewGetExtension< / tt > provides a slower alternative:
< blockquote > < pre > if (GL_TRUE == glewGetExtension("GL_ARB_fragment_program"))
{
/* Looks like ARB_fragment_program is supported. */
}
< / pre > < / blockquote >
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< p >
< font size = "+1" > < b > Experimental drivers< / b > < / font >
< p >
GLEW works by querying the supported extensions from the graphics
driver. Experimental 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
< tt > glewExperimental< / tt > global switch can be turned on by setting it
to < tt > GL_TRUE< / tt > before calling < tt > glewInit()< / tt > . This makes
sure that all extensions with valid entry points will be exposed.
< p >
< font size = "+1" > < b > Platform specific extensions< / b > < / font >
< p >
Platform specific extensions are separated into two header files:
< tt > wglew.h< / tt > and < tt > glxew.h< / tt > . These files define the
available < tt > WGL< / tt > and < tt > GLX< / tt > extensions as well as the
global < tt > wglew< / tt > and < tt > glxew< / tt > structs, which work similarly
to the < tt > glew< / tt > structure. To determine if a given < tt > WGL< / tt > or
< tt > GLX< / tt > extension is supported, query < tt > wglew.{extension name}< / tt > or
< tt > glxew.{extension_name}< / tt > . For example:
< blockquote > < pre > #include < GL/wglew.h>
if (wglew.ARB_pbuffer)
{
/* OK, we can use pbuffers */
}
else
{
/* Sorry, pbuffers will not work on this platform */
}
< / pre > < / blockquote >
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name="Utilities">< font size = "+1" > < b > Utilities< / b > < / font > < / a >
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GLEW provides two command line tools: one for creating a list of
available extensions and visuals; and another for verification of extension
entry points.
< p >
< font size = "+1" > < b > wglinfo: reporting extensions and visuals on Windows< / b > < / font >
< p >
< tt > wglinfo< / tt > is the Windows version of < tt > glxinfo< / tt > . By
default it creates a file called < tt > wglinfo.txt< / tt > containing
a list of available OpenGL, WGL, and GLU extensions
as well as a table of visuals, aka. pixelformats. PBuffer and multiple output
capable visuals are also included. The format of the table is
described < a href = "wglinfo.txt" > here< / a > . For additional usage information, type
< tt > wglinfo -h< / tt > .
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< p >
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< font size = "+1" > < b > glewinfo: extension verification utility< / b > < / font >
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< p >
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< tt > glewinfo< / tt > allows you to verify the entry points for the
extensions supported on your platform. It uses GLEW to find out which extensions
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and entry points are available and reports the results to a text file
called < tt > glewinfo.txt< / tt > .
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< td bgcolor = "#FFF0D0" align = "center" > < a
name="Issues">< font size = "+1" > < b > Known Issues< / b > < / font > < / a >
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< td >
GLEW requires GLX 1.2 to assure compatibility with GLUT. In addition,
the SGI GLX video extensions are not supported, because they depend on
external libraries.
< p >
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Note that according to the < a
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href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/opengl/ntopnglr_6yer.asp">WGL documentation< / a > you have to initialize the entry points
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for every rendering context you create. GLEW ignores this
requirement, and does not define per context entry points. This means
that you need to call < tt > glewInit()< / tt > only once in your program,
or more precisely once per process. We have not noticed any problems
so far from ignoring the specification.
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< td bgcolor = "#FFF0D0" align = "center" > < a
name="Credits">< font size = "+1" > < b > Credits, Copyright< / b > < / font > < / a >
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< td >
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GLEW was developed by Milan Ikits. He also performs occasional
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maintainance to make sure that GLEW stays in mint condition. Aaron
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Lefohn, Joe Kniss, and Chris Wyman were the first users and also
assisted with the design and debugging process. The acronym
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originates from Aaron Lefohn. The RPM packages are maintained by Karol
Pietrzak. Nate Robins created the < tt > wglinfo< / tt > utility,
to which modifications were added by Michael Wimmer.
< p >
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< p >
GLEW is derived from the EXTGL project by Lev Povalahev. It is
licensed under the LGPL, the BSD license, the SGI Free Software
License B, and the GLX Public License. We encourage those who are not
in favor of the LGPL to read < a
href="http://www.cs.utah.edu/~gk/teem/lgpl.html">this< / a > excellent
tutorial.
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< i > Last update: 02-03-03< / i > < / td >
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