<!-- begin header.html --> <!-- The OpenGL Extension Wrangler Library Copyright (C) 2002-2008, Milan Ikits <milan ikits[]ieee org> Copyright (C) 2002-2008, Marcelo E. Magallon <mmagallo[]debian org> Copyright (C) 2002, Lev Povalahev All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. * The name of the author may be used to endorse or promote products derived from this software without specific prior written permission. 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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: </p> <p class="pre"> #include <GL/glew.h><br> #include <GL/glut.h><br> ...<br> glutInit(&argc, argv);<br> glutCreateWindow("GLEW Test");<br> GLenum err = glewInit();<br> if (GLEW_OK != err)<br> {<br> /* Problem: glewInit failed, something is seriously wrong. */<br> fprintf(stderr, "Error: %s\n", glewGetErrorString(err));<br> ...<br> }<br> fprintf(stdout, "Status: Using GLEW %s\n", glewGetString(GLEW_VERSION));<br> </p> <h2>Checking for Extensions</h2> <p> 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 <tt>GLEW_{extension_name}</tt>: </p> <p class="pre"> if (GLEW_ARB_vertex_program)<br> {<br> /* It is safe to use the ARB_vertex_program extension here. */<br> glGenProgramsARB(...);<br> }<br> </p> <p> <b>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.</b> </p> <p> You can also check for core OpenGL functionality. For example, to see if OpenGL 1.3 is supported, do the following: </p> <p class="pre"> if (GLEW_VERSION_1_3)<br> {<br> /* Yay! OpenGL 1.3 is supported! */<br> }<br> </p> <p> In general, you can check if <tt>GLEW_{extension_name}</tt> or <tt>GLEW_VERSION_{version}</tt> is true or false. </p> <p> It is also possible to perform extension checks from string input. Starting from the 1.3.0 release, use <tt>glewIsSupported</tt> to check if the required core or extension functionality is available: </p> <p class="pre"> if (glewIsSupported("GL_VERSION_1_4 GL_ARB_point_sprite"))<br> {<br> /* Great, we have OpenGL 1.4 + point sprites. */<br> }<br> </p> <p> For extensions only, <tt>glewGetExtension</tt> provides a slower alternative (GLEW 1.0.x-1.2.x). <b>Note that in the 1.3.0 release </b> <tt>glewGetExtension</tt> <b>was replaced with </b> <tt>glewIsSupported</tt>. </p> <p class="pre"> if (glewGetExtension("GL_ARB_fragment_program"))<br> {<br> /* Looks like ARB_fragment_program is supported. */<br> }<br> </p> <h2>Experimental Drivers</h2> <p> 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 <tt>glewExperimental</tt> global switch can be turned on by setting it to <tt>GL_TRUE</tt> before calling <tt>glewInit()</tt>, which ensures that all extensions with valid entry points will be exposed. </p> <h2>Platform Specific Extensions</h2> <p> Platform specific extensions are separated into two header files: <tt>wglew.h</tt> and <tt>glxew.h</tt>, which define the available <tt>WGL</tt> and <tt>GLX</tt> extensions. To determine if a certain extension is supported, query <tt>WGLEW_{extension name}</tt> or <tt>GLXEW_{extension_name}</tt>. For example: </p> <p class="pre"> #include <GL/wglew.h><br> <br> if (WGLEW_ARB_pbuffer)<br> {<br> /* OK, we can use pbuffers. */<br> }<br> else<br> {<br> /* Sorry, pbuffers will not work on this platform. */<br> }<br> </p> <p> Alternatively, use <tt>wglewIsSupported</tt> or <tt>glxewIsSupported</tt> to check for extensions from a string: </p> <p class="pre"> if (wglewIsSupported("WGL_ARB_pbuffer"))<br> {<br> /* OK, we can use pbuffers. */<br> }<br> </p> <h2>Utilities</h2> <p> GLEW provides two command-line utilities: one for creating a list of available extensions and visuals; and another for verifying extension entry points. </p> <h3>visualinfo: extensions and visuals</h3> <p> <tt>visualinfo</tt> is an extended version of <tt>glxinfo</tt>. The Windows version creates a file called <tt>visualinfo.txt</tt>, 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 <tt>visualinfo -h</tt>. </p> <h3>glewinfo: extension verification utility</h3> <p> <tt>glewinfo</tt> 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 <tt>glewinfo.txt</tt>. The Unix version prints the results to <tt>stdout</tt>. </p> <p>Windows usage:</p> <blockquote><pre>glewinfo [-pf <id>]</pre></blockquote> <p>where <tt><id></tt> is the pixel format id for which the capabilities are displayed.</p> <p>Unix usage:</p> <blockquote><pre>glewinfo [-display <dpy>] [-visual <id>]</pre></blockquote> <p>where <tt><dpy></tt> is the X11 display and <tt><id></tt> is the visual id for which the capabilities are displayed.</p> <!-- begin footer.html --> </td></tr></table></body> <!-- end footer.html -->