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493 lines
16 KiB
HTML
493 lines
16 KiB
HTML
<!--
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Copyright (C) 2003, 2002, Milan Ikits <milan.ikits@ieee.org>
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Copyright (C) 2003, 2002, Marcelo E. Magallon <mmagallo@debian.org>
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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" "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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<link href="glew.css" type=text/css rel=stylesheet>
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</head>
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<body bgcolor="#fff0d0">
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<center>
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<table border=0 width="60%" cellpadding="5" cellspacing="5">
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<tr>
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<td bgcolor="#ffffff" align=center><br><p><img src="./glew.png" alt="glew" width="97" height="75">
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<p>
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<font size="+2"><b>The OpenGL Extension Wrangler Library</b></font>
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<p>
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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="#Utilities"><font size="-1">Utilities</font></a></td></tr>
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<tr><td align=center><a href="#Auto"><font size="-1">Automatic Code Generation</font></a></td></tr>
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<tr><td align=center><a href="#Namespace"><font size="-1">Separate Namespace</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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<tr><td align=center><br></td></tr>
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</table>
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</tr>
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<tr><td bgcolor="#fff0d0" align="center"></td></tr>
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<tr>
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<td bgcolor="#ffffff">
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<center><a name="Introduction"><font size="+1"><b>Introduction</b></font></a></center>
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<p>
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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 SGI systems and PCs with commodity graphics cards
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on three operating systems: Windows, Linux, and IRIX.
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<p>
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</td>
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</tr>
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<tr><td bgcolor="#fff0d0" align="center"></td></tr>
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<tr>
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<td bgcolor="#ffffff">
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<center><a name="Download"><font size="+1"><b>Obtaining GLEW</b></font></a></center>
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<p>
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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><td bgcolor="#fff0d0" align="center"></td></tr>
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<tr>
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<td bgcolor="#ffffff">
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<center><a name="Supported"><font size="+1"><b>Supported Extensions</b></font></a></center>
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<p>
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GLEW currently supports the following extensions:
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<ul>
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<li><a href="glew.html">OpenGL extensions</a>
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<li><a href="wglew.html">WGL extensions</a>
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<li><a href="glxew.html">GLX extensions</a>
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</ul>
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<p>
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Useful links about OpenGL extensions:
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<ul>
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<li><a
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href="http://www.opengl.org/developers/code/features/OGLextensions/OGLextensions.html">
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All About OpenGL Extensions</a>
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<li><a href="http://oss.sgi.com/projects/ogl-sample/registry/">OpenGL Extension Registry</a>
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<li><a
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href="http://www.ati.com/developer/sdk/radeonSDK/html/info/Prog3D.html">ATI
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OpenGL Extension Specifications</a>
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<li><a
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href="http://developer.nvidia.com/view.asp?IO=nvidia_opengl_specs">NVIDIA
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OpenGL Extension Specifications</a>
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</ul>
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<p>
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</td>
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</tr>
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<tr><td bgcolor="#fff0d0" align="center"></td></tr>
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<tr>
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<td bgcolor="#ffffff">
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<center><a name="Build"><font size="+1"><b>How to Build Your Project with GLEW</b></font></a></center>
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<p>
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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">Including the source files / project file</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 on Windows define the
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<tt>GLEW_STATIC</tt> preprocessor constant for the static library or
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executable you are building together with GLEW. You also need to
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replace <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. 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_static.dsp</tt> to your workspace (solution) and compile it together
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with your other projects. In this case you need to change the
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<tt>GLEW_BUILD</tt> preprocessor constant to <tt>GLEW_STATIC</tt>,
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otherwise you get build errors. <b>Note that GLEW does not use the C
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runtime library, so it does not matter which version (single-threaded,
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multi-threaded or multi-threaded DLL) it is linked with</b>.
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<p>
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<font size="+1">Using GLEW as a shared library</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 and IRIX (<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><td bgcolor="#fff0d0" align="center"></td></tr>
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<tr>
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<td bgcolor="#ffffff">
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<center><a name="Install"><font size="+1"><b>How to Install GLEW</b></font></a></center>
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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/shared/glew32.dll</tt></td><td> to </td>
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<td><tt>%SystemRoot%/system32</tt></td></tr>
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<tr><td><tt>lib/shared/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.
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<p>
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On Linux and IRIX, 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_DEST</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><td bgcolor="#fff0d0" align="center"></td></tr>
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<tr>
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<td bgcolor="#ffffff">
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<center><a name="Use"><font size="+1"><b>How to Use GLEW</b></font></a></center>
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<p>
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<font size="+1">Initializing GLEW</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">Querying the available OpenGL extensions</font>
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<p>
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Starting from GLEW 1.1.0, you can find out if a particular extension
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is available on your platform by querying globally defined variables
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of the form <tt>GLEW_{extension_name}</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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<b>In GLEW 1.0.x, a global structure was used for this task. To ensure
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binary compatibility between releases, the struct was replaced with a
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set of variables.</b>
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<p>
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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:
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<blockquote><pre>if (GLEW_VERSION_1_3)
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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_VERSION_{version}</tt> is set or not.
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<p>
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For extensions <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">Experimental drivers</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">Platform specific extensions</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>, which define the available
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<tt>WGL</tt> and <tt>GLX</tt> extensions. To determine if a certain
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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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<tr><td bgcolor="#fff0d0" align="center"></td></tr>
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<tr>
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<td bgcolor="#ffffff">
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<center><a name="Utilities"><font size="+1"><b>Utilities</b></font></a></center>
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<p>
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GLEW provides two command line tools: one for creating a list of
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available extensions and visuals; and another for verification of extension
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entry points.
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<p>
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<font size="+1">wglinfo: extensions and visuals on Windows</font>
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<p>
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<tt>wglinfo</tt> is the Windows version of <tt>glxinfo</tt>. By
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default it creates a file called <tt>wglinfo.txt</tt> that contains
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a list of available OpenGL, WGL, and GLU extensions
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as well as a table of visuals aka. pixelformats. Pbuffer and multiple output
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capable visuals are also included. The format of the table is
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described <a href="wglinfo.txt">here</a>. For additional usage information, type
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<tt>wglinfo -h</tt>.
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<p>
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<font size="+1">glewinfo: extension verification utility</font>
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<p>
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<tt>glewinfo</tt> allows you to verify the entry points for the
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extensions supported on your platform. It uses GLEW to find out which extensions
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and entry points are available. On Windows it reports the results to a text file
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called <tt>glewinfo.txt</tt>, on Linux and IRIX it prints them to <tt>stdout</tt>.
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<p>
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</td>
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</tr>
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<tr><td bgcolor="#fff0d0" align="center"></td></tr>
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<tr>
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<td bgcolor="#ffffff">
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<center><a name="Auto"><font size="+1"><b>Automatic Code Generation</b></font></a></center>
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<p>
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Starting from release 1.1.0, the source code and parts of the
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documentation are automatically generated from the extension
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specifications via a two-step process. In the first step,
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specification files from the registry are parsed and skeleton
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descriptors are created for each extension. These descriptors contain
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all necessary information for creating the source code and
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documentation in a simple and compact format, including the the
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extension name, url, tokens, function declarations, typedefs and
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struct definitions. In the second step, the header files as well as
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the library and glewinfo source are generated from the descriptor
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files. The code generation scripts are located in the <tt>auto</tt>
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subdirectory.
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<p>
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</td>
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</tr>
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<tr><td bgcolor="#fff0d0" align="center"></td></tr>
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<tr>
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<td bgcolor="#ffffff">
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<center><a name="Namespace"><font size="+1"><b>Separate Namespace</b></font></a></center>
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<p>
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To avoid name clashes when linking with libraries that include the
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same symbol, extension entry points are declared in a separate
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namespace (release 1.1.0 and up). This is achieved by aliasing OpenGL
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function names to their GLEW equivalents. For instance,
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<tt>glFancyFunction</tt> is simply an alias to
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<tt>glewFancyFunction</tt>. Note that the separate namespace doesn't
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effect token and function pointer definitions.
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<p>
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</td>
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</tr>
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<tr><td bgcolor="#fff0d0" align="center"></td></tr>
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<tr>
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<td bgcolor="#ffffff">
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<center><a name="Issues"><font size="+1"><b>Known Issues</b></font></a></center>
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<p>
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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 currently not supported.
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<p>
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Note that according to some <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><td bgcolor="#fff0d0" align="center"></td></tr>
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<tr>
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<td bgcolor="#ffffff">
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<center><a name="Credits"><font size="+1"><b>Credits, Copyright</b></font></a></center>
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<p>
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GLEW was developed by Milan Ikits and Marcelo Magallon. They also
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perform occasional maintainance to make sure that GLEW stays in mint
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|
condition. Aaron Lefohn, Joe Kniss, and Chris Wyman were the first
|
|
users and also assisted with the design and debugging process. The
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acronym GLEW originates from Aaron Lefohn. Pasi Kärkkäinen
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|
identified and fixed several problems with GLX and SDL. The RPM
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packages are maintained by Karol Pietrzak. Nate Robins created the
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<tt>wglinfo</tt> utility, to which modifications were added by Michael
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Wimmer.
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<p>
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<p>
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GLEW is originally derived from the <a
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|
href="http://www.levp.de/3d/">EXTGL</a> project by Lev Povalahev. The
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source code is licensed under the modified BSD license, the <a
|
|
href="sgi.txt">SGI Free Software License B</a>, and the <a
|
|
href="glx.txt">GLX Public License</a>. The automatic code
|
|
generation scripts are released under the <a href="gpl.txt">GPL</a>.
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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="right">
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<i>Last update: 07-07-03</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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