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413 lines
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413 lines
13 KiB
HTML
<!--
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Copyright (C) 2002 Milan Ikits
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This documentation may not be modified or redistributed in any
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form, except by the copyright holder.
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-->
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
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"http://www.w3.org/TR/html/4/loose.dtd">
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<html>
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<head>
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<title>
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GLEW: The OpenGL Extension Wrangler Library
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</title>
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<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
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</head>
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<body bgcolor="#ffffff" text="#000000" link="#1010f0" vlink="#000080" alink="#800000">
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<center>
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<table border=0 width="50%" cellpadding="5" cellspacing="10">
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<tr>
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<td align=center><img src="./glew.png" alt="glew" width="97" height="75"></td>
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</tr>
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<tr>
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<td align=center><font size="+2"><b>The OpenGL Extension Wrangler Library</b></font></td>
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</tr>
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<tr>
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<td width="80%">
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<table border=0 cellpadding=0 cellspacing=0 align=center>
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<tr><td align=center><a href="#Introduction"><font size="-1">Introduction</font></a></td></tr>
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<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>
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<tr><td align=center><a href="#Install"><font size="-1">How to Install GLEW</font></a></td></tr>
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<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="#Issues"><font size="-1">Known Issues</font></a></td></tr>
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<tr><td align=center><a href="#Credits"><font size="-1">Credits, Copyright</font></a></td></tr>
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</table>
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<br>
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</td>
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</tr>
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<tr>
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<td bgcolor="#FFF0D0" align="center"><a
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name="Introduction"><font size="+1"><b>Introduction</b></font></a>
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</td>
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</tr>
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<tr>
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<td>
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The goal of the OpenGL Extension Wrangler Library (GLEW) is to assist
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C/C++ OpenGL developers with two tedious tasks: initializing and
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using extensions and writing portable applications. GLEW provides
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an efficient run-time mechanism to determine whether a certain
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extension is supported by the driver or not. OpenGL core and
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extension functionality is exposed via a single header file. GLEW
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currently supports the products of two commodity graphics card
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vendors, NVIDIA and ATI, on two operating systems, Windows and Linux.
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<p>
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</td>
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</tr>
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<tr>
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<td bgcolor="#FFF0D0" align="center"><a
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name="Download"><font size="+1"><b>Obtaining GLEW</b></font></a>
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</td>
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</tr>
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<tr>
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<td>
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The source and precompiled binaries are available at the <a
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href="http://glew.sourceforge.net/">project website</a>.
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<p>
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</td>
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</tr>
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<tr>
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<td bgcolor="#FFF0D0" align="center"><a
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name="Supported"><font size="+1"><b>Supported Extensions</b></font></a>
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</td>
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</tr>
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<tr>
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<td>
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<table border=0 cellpadding="0" cellspacing="0">
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<tr>
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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>
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extensions.
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</td>
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</tr>
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</table>
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<p>
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</td>
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</tr>
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<tr>
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<td bgcolor="#FFF0D0" align="center"><a
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name="Build"><font size="+1"><b>How to Build Your Project with GLEW</b></font></a>
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</td>
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</tr>
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<tr>
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<td>
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There are two ways to build your project with GLEW.
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<p>
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<font size="+1"><b>Including the source files / project file</b></font>
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<p>
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The simpler but less flexible way is to include <tt>glew.h</tt> and
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<tt>glew.c</tt> into your project and define the <tt>GLEW_STATIC</tt>
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preprocessor constant for the static library or executable you are
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building together with GLEW. You also need to replace
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<tt><GL/gl.h></tt> and <tt><GL/glu.h></tt> with
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<tt><glew.h></tt> and set the appropriate include flag
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(<tt>-I</tt>) to tell the compiler where to look for it.
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For example:
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<blockquote><pre>#include <glew.h>
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#include <GL/glut.h>
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<gl, glu, and glut functionality is available here>
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</pre></blockquote>
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Note that if you are using GLEW together with GLUT, you have to
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include <tt>glew.h</tt> first. In addition, <tt>glew.h</tt> includes
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<tt>glu.h</tt>, so you don't need to include it separately.
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<p>
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On Windows you can also add the supplied project file
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(<tt>glew.dsp</tt> or <tt>glew.vcproj</tt>) to your workspace or
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solution and compile it together with your other projects. In this
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case you need to change the <tt>GLEW_BUILD</tt> preprocessor constant
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to <tt>GLEW_STATIC</tt>, otherwise you get build errors. <b>Note that
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GLEW does not use the C runtime library, so it does not matter
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which version (single-threaded, multi-threaded or multi-threaded DLL) it
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is linked with</b>.
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<p>
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<font size="+1"><b>Using GLEW as a shared library</b></font>
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<p>
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Alternatively, you can use the provided project files / makefile to
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build a separate shared library you can link your projects with later.
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In this case the best practice is to install <tt>glew.h</tt>,
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<tt>glew32.lib</tt>, and <tt>glew32.dll</tt> / <tt>libGLEW.so</tt> to
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where the OpenGL equivalents <tt>gl.h</tt>, <tt>opengl32.lib</tt>, and
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<tt>opengl32.dll</tt> / <tt>libGL.so</tt> are located. Note that you
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need administrative privileges to do this. If you do not have
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administrator access and your system administrator will not do it for
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you, you can install GLEW into your own lib and include subdirectories
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and tell the compiler where to find it. Then you can just replace
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<tt><GL/gl.h></tt> with <tt><GL/glew.h></tt> in your
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program:
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<blockquote><pre>#include <GL/glew.h>
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#include <GL/glut.h>
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<gl, glu, and glut functionality is available here>
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</pre></blockquote>
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or:
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<blockquote><pre>#include <GL/glew.h>
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<gl and glu functionality is available here>
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</pre></blockquote>
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<p>
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Don't forget to link your project with <tt>glew32.lib</tt>,
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<tt>glu32.lib</tt>, and <tt>opengl32.lib</tt> on Windows and
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<tt>libGLEW.so</tt>, <tt>libGLU.so</tt>, and <tt>libGL.so</tt> on
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Linux (<tt>-lGLEW -lGLU -lGL</tt>).
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<p>
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It is important to keep in mind that <tt>glew.h</tt> includes neither
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<tt>windows.h</tt> nor <tt>gl.h</tt>. Also, GLEW will warn you by
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issuing a preprocessor error in case you have included <tt>gl.h</tt>,
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<tt>glext.h</tt>, or <tt>glATI.h</tt> before <tt>glew.h</tt>.
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<p>
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</td>
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</tr>
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<tr>
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<td bgcolor="#FFF0D0" align="center"><a
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name="Install"><font size="+1"><b>How to Install GLEW</b></font></a>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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To install the shared library version of GLEW you need to copy the
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headers and libraries into their destination directories. On Windows
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this boils down to copying (no, we will not write a Windows installer
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for you).
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<p>
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<center>
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<table border=0 cellpadding=0 cellspacing=0>
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<tr><td><tt>lib/glew32.dll</tt></td><td> to </td>
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<td><tt>%SystemRoot%/system32</tt>, usually <tt>C:/WINDOWS/system32</tt></td></tr>
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<tr><td><tt>lib/glew32.lib</tt></td><td> to </td>
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<td><tt>{VC Root}/Lib</tt></td></tr>
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<tr><td><tt>include/GL/glew.h</tt></td><td> to </td>
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<td><tt>{VC Root}/Include/GL</tt></td></tr>
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<tr><td><tt>include/GL/wglew.h</tt></td><td> to </td>
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<td><tt>{VC Root}/Include/GL</tt></td></tr>
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</table>
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</center>
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<p>
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where <tt>{VC Root}</tt> is your Visual C++ directory, typically
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<tt>C:/Program Files/Microsoft Visual Studio/VC98</tt> for Visual
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Studio 6.0 or <tt>C:/Program Files/Microsoft Visual
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Studio/Vc7/PlatformSDK</tt> for Visual Studio .NET. <b>However, if you
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build GLEW with Visual Studio .NET, the project file will
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automatically install it into these directories, so you
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don't have to worry about installation at all</b>.
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<p>
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On Linux, typing <tt>"make install"</tt> will attempt to install GLEW
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into <tt>/usr/include/GL</tt> and <tt>/usr/lib</tt>. You can
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customize the installation target via the <tt>GLEW_TARGET</tt>
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environment variable if you do not have write access
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to these directories.
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<p>
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</td>
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</tr>
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<tr>
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<td bgcolor="#FFF0D0" align="center"><a
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name="Use"><font size="+1"><b>How to Use GLEW</b></font></a>
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</td>
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</tr>
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<tr>
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<td>
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<font size="+1"><b>Initializing GLEW</b></font>
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<p>
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First you need to create a valid OpenGL rendering context and call
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<tt>glewInit()</tt> to initialize the extension entry points. If
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<tt>glewInit()</tt> returns <tt>GLEW_OK</tt> the initialization
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succeeded and you can use the available extensions as well as core
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OpenGL functionality. For example:
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<blockquote><pre>#include <GL/glew.h>
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#include <GL/glut.h>
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...
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glutInit(&argc, argv);
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glutCreateWindow("GLEW Test");
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int err = glewInit();
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if (GLEW_OK != err)
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{
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/* problem: glewInit failed, something is seriously wrong */
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fprintf(stderr, "Error: %s\n", glewGetErrorString(err));
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...
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}
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</pre></blockquote>
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<p>
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<font size="+1"><b>Querying the available OpenGL extensions</b></font>
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<p>
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To find out if a particular extension is available on your
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platform, use the globally defined structure <tt>glew</tt>:
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<blockquote><pre>if (glew.ARB_vertex_program)
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{
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/* it is safe to use the ARB_vertex_program extension here */
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glGenProgramsARB(...);
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}
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</pre></blockquote>
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You can also check for core OpenGL functionality. For example, to
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see if OpenGL 1.3 is supported you can use the following:
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<blockquote><pre>if (glew.GL_13)
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{
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/* Yay! OpenGL 1.3 is supported! */
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}
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</pre></blockquote>
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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
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<tt>glewGetExtension</tt> provides a slower alternative:
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<blockquote><pre>if (GL_TRUE == glewGetExtension("GL_ARB_fragment_program"))
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{
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/* Looks like ARB_fragment_program is supported. */
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}
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</pre></blockquote>
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<p>
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<font size="+1"><b>Experimental drivers</b></font>
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<p>
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GLEW works by querying the supported extensions from the graphics
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driver. Experimental drivers, however, might not report every
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available extension through the standard mechanism, in which case GLEW
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will report it unsupported. To circumvent this situation, the
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<tt>glewExperimental</tt> global switch can be turned on by setting it
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to <tt>GL_TRUE</tt> before calling <tt>glewInit()</tt>. This makes
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sure that all extensions with valid entry points will be exposed.
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<p>
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<font size="+1"><b>Platform specific extensions</b></font>
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<p>
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Platform specific extensions are separated into two header files:
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<tt>wglew.h</tt> and <tt>glxew.h</tt>. These files define the
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available <tt>WGL</tt> and <tt>GLX</tt> extensions as well as the
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global <tt>wglew</tt> and <tt>glxew</tt> structs, which work similarly
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to the <tt>glew</tt> structure. To determine if a given <tt>WGL</tt> or
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<tt>GLX</tt> extension is supported, query <tt>wglew.{extension name}</tt> or
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<tt>glxew.{extension_name}</tt>. For example:
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<blockquote><pre>#include <GL/wglew.h>
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if (wglew.ARB_pbuffer)
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{
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/* OK, we can use pbuffers */
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}
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else
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{
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/* Sorry, pbuffers will not work on this platform */
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}
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</pre></blockquote>
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<p>
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<font size="+1"><b>glewinfo: a command line extension reporting utility</b></font>
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<p>
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GLEW comes with a command line utility called <tt>glewinfo</tt> that
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allows you to make a list of the extensions supported on your platform.
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The <tt>glewinfo</tt> utility uses GLEW to find out which extensions
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and entry points are available and reports the results to a text file
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called <tt>glewinfo.txt</tt>.
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<p>
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</td>
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</tr>
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<tr>
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<td bgcolor="#FFF0D0" align="center"><a
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name="Issues"><font size="+1"><b>Known Issues</b></font></a>
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</td>
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</tr>
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<tr>
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<td>
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GLEW requires GLX 1.2 to assure compatibility with GLUT. In addition,
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the SGI GLX video extensions are not supported, because they depend on
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external libraries.
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<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
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requirement, and does not define per context entry points. This means
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that you need to call <tt>glewInit()</tt> only once in your program,
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or more precisely once per process. We have not noticed any problems
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so far from ignoring the specification.
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<p>
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</td>
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</tr>
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<tr>
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<td bgcolor="#FFF0D0" align="center"><a
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name="Credits"><font size="+1"><b>Credits, Copyright</b></font></a>
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</td>
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</tr>
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<tr>
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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
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assisted with the design and debugging process. The acronym
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originates from Aaron Lefohn.
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<p>
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GLEW is derived from the EXTGL project by Lev Povalahev. It is
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licensed under the LGPL, the BSD license, the SGI Free Software
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License B, and the GLX Public License. We encourage those who are not
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in favor of the LGPL to read <a
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href="http://www.cs.utah.edu/~gk/teem/lgpl.html">this</a> excellent
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tutorial.
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<blockquote><pre></pre></blockquote>
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<tr>
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<td bgcolor="#FFF0D0">
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<table border="0" cellspacing="0" cellpadding="0" width="100%">
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<tr>
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<td align="left">
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<i>Last update: 12-26-02</i></td>
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</tr>
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</table>
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</td>
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</tr>
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</table>
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</center>
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</body>
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