brkho
/
mesa


			
				
					
						
						
							1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980
							<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() --&gt; _mesa_Foo()
  OpenGL ES:  glFoo() --&gt; _es_Foo() --&gt; _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>