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<html>
<title>OpenGL ES</title>
<head><link rel="stylesheet" type="text/css" href="mesa.css"></head>
<body>
<h1>OpenGL ES</h1>
<p>Mesa implements OpenGL ES 1.1 and OpenGL ES 2.0. More informations about
OpenGL ES can be found at <a href="http://www.khronos.org/opengles/"
target="_parent"> http://www.khronos.org/opengles/</a>.</p>
<p>OpenGL ES depends on a working EGL implementation. Please refer to
<a href="egl.html">Mesa EGL</a> for more information about EGL.</p>
<h2>Build the Libraries</h2>
<ol>
<li>Run <code>configure</code> with <code>--enable-gles-overlay</code> and enable the Gallium driver for your hardware.</li>
<li>Build and install Mesa as usual.</li>
</ol>
Alternatively, if XCB-DRI2 is installed on the system, one can use
<code>egl_dri2</code> EGL driver with OpenGL|ES-enabled DRI drivers
<ol>
<li>Run <code>configure</code> with <code>--enable-gles1 --enable-gles2</code>.</li>
<li>Build and install Mesa as usual.</li>
</ol>
<p>Both methods will install libGLESv1_CM, libGLESv2, libEGL, and one or more
EGL drivers for your hardware.</p>
<h2>Run the Demos</h2>
<p>There are some demos in <code>progs/egl/</code>. You can use them to test
your build. For example,</p>
<pre>
$ cd progs/egl/eglut
$ make
$ cd ../opengles1
$ make
$ ./torus_x11
</pre>
<h2>Developers</h2>
<h3>Internal Libraries</h3>
<table border="1" style="text-align: center;">
<tr><td>Library Name</td><td>Used By</td><td>Enabled</td><td>OpenGL</td><td>OpenGL ES 1.x</td><td>OpenGL ES 2.x</td></tr>
<tr><td><code>libmesa.a</td><td>Classic DRI drivers</td><td>y</td><td>y</td><td>--enable-gles1</td><td>--enable-gles2</td></tr>
<tr><td><code>libmesagallium.a</td><td>Gallium EGL and DRI drivers</td><td>y</td><td>y</td><td>--enable-gles1</td><td>--enable-gles2</td></tr>
<tr><td><code>libes1gallium.a</td><td>Gallium EGL drivers</td><td>--enable-gles-overlay</td><td>n</td><td>y</td><td>n</td></tr>
<tr><td><code>libes2gallium.a</td><td>Gallium EGL drivers</td><td>--enable-gles-overlay</td><td>n</td><td>n</td><td>y</td></tr>
</table>
<h3>Dispatch Table</h3>
<p>OpenGL ES has an additional indirection when dispatching fucntions</p>
<pre>
Mesa: glFoo() --> _mesa_Foo()
OpenGL ES: glFoo() --> _es_Foo() --> _mesa_Foo()
</pre>
<p>The indirection serves several purposes</p>
<ul>
<li>When a function is in Mesa and the type matches, it checks the arguments and calls the Mesa function.</li>
<li>When a function is in Mesa but the type mismatches, it checks and converts the arguments before calling the Mesa function.</li>
<li>When a function is not available in Mesa, or accepts arguments that are not available in OpenGL, it provides its own implementation.</li>
</ul>
<p>Other than the last case, OpenGL ES uses <code>APIspec.xml</code> to generate functions to check and/or converts the arguments.</p>
</body>
</html>
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