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| GLEW: The OpenGL Extension Wrangler Library | |
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| <tr><td align="center"><i>Latest Release: <a href="https://sourceforge.net/project/showfiles.php?group_id=67586&package_id=67942&release_id=504079">1.4.0</a></i></td></tr> | |
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| <tr><td align="center"><i>Last Update: 04-27-07</i></td></tr> | |
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| <h1>The OpenGL Extension Wrangler Library</h1> | |
| <h2>Initializing GLEW</h2> | |
| <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: | |
| </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> | |
| </td> | |
| </tr> | |
| </table> | |
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