89 lines
2.3 KiB
HTML
89 lines
2.3 KiB
HTML
<HTML>
|
|
|
|
<TITLE>Off-screen Rendering</TITLE>
|
|
|
|
<link rel="stylesheet" type="text/css" href="mesa.css"></head>
|
|
|
|
<BODY>
|
|
|
|
<H1>Off-screen Rendering</H1>
|
|
|
|
|
|
<p>
|
|
Mesa's off-screen rendering interface is used for rendering into
|
|
user-allocated blocks of memory.
|
|
That is, the GL_FRONT colorbuffer is actually a buffer in main memory,
|
|
rather than a window on your display.
|
|
There are no window system or operating system dependencies.
|
|
One potential application is to use Mesa as an off-line, batch-style renderer.
|
|
</p>
|
|
|
|
<p>
|
|
The <B>OSMesa</B> API provides three basic functions for making off-screen
|
|
renderings: OSMesaCreateContext(), OSMesaMakeCurrent(), and
|
|
OSMesaDestroyContext(). See the Mesa/include/GL/osmesa.h header for
|
|
more information about the API functions.
|
|
</p>
|
|
|
|
<p>
|
|
There are several examples of OSMesa in the <code>progs/osdemo/</code>
|
|
directory.
|
|
</p>
|
|
|
|
|
|
<H2>Deep color channels</H2>
|
|
|
|
<p>
|
|
For some applications 8-bit color channels don't have sufficient
|
|
precision.
|
|
OSMesa supports 16-bit and 32-bit color channels through the OSMesa interface.
|
|
When using 16-bit channels, channels are GLushorts and RGBA pixels occupy
|
|
8 bytes.
|
|
When using 32-bit channels, channels are GLfloats and RGBA pixels occupy
|
|
16 bytes.
|
|
</p>
|
|
|
|
<p>
|
|
Before version 6.5.1, Mesa had to be recompiled to support exactly
|
|
one of 8, 16 or 32-bit channels.
|
|
With Mesa 6.5.1, Mesa can be compiled for either 8, 16 or 32-bit channels
|
|
and render into any of the smaller size channels.
|
|
For example, if Mesa's compiled for 32-bit channels, you can also render
|
|
16 and 8-bit channel images.
|
|
</p>
|
|
|
|
<p>
|
|
To build Mesa/OSMesa for 16 and 8-bit color channel support:
|
|
<pre>
|
|
make realclean
|
|
make linux-osmesa16
|
|
</pre>
|
|
|
|
<p>
|
|
To build Mesa/OSMesa for 32, 16 and 8-bit color channel support:
|
|
<pre>
|
|
make realclean
|
|
make linux-osmesa32
|
|
</pre>
|
|
|
|
<p>
|
|
You'll wind up with a library named libOSMesa16.so or libOSMesa32.so.
|
|
Otherwise, most Mesa configurations build an 8-bit/channel libOSMesa.so library
|
|
by default.
|
|
</p>
|
|
|
|
<p>
|
|
If performance is important, compile Mesa for the channel size you're
|
|
most interested in.
|
|
</p>
|
|
|
|
<p>
|
|
If you need to compile on a non-Linux platform, copy Mesa/configs/linux-osmesa16
|
|
to a new config file and edit it as needed. Then, add the new config name to
|
|
the top-level Makefile. Send a patch to the Mesa developers too, if you're
|
|
inclined.
|
|
</p>
|
|
|
|
</BODY>
|
|
</HTML>
|