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3<TITLE>Off-screen Rendering</TITLE>
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7<H1>Off-screen Rendering</H1>
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10<p>
11Mesa 1.2.4 introduced off-screen rendering, a facility for generating
123-D imagery without having to open a window on your display.  Mesa's
13simple off-screen rendering interface is completely operating system
14and window system independent so programs which use off-screen
15rendering should be very portable.  This feature effectively
16enables you to use Mesa as an off-line, batch-oriented renderer.
17</p>
18<p>
19The "OSMesa" API provides 3 functions for making off-screen
20renderings: OSMesaCreateContext(), OSMesaMakeCurrent(), and
21OSMesaDestroyContext().  See the Mesa/include/GL/osmesa.h header for
22more information.  See the demos/osdemo.c file for an example program.
23There is no facility for writing images to files.  That's up to you.
24</p>
25<p>
26If you want to generate large images (larger than 1280x1024) you'll
27have to edit the src/config.h file to change MAX_WIDTH and MAX_HEIGHT
28then recompile Mesa.  Image size should only be limited by available
29memory.
30</p>
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32
33<H2>Deep color channels</H2>
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35<p>
36   For some applications 8-bit color channels don't have sufficient
37   accuracy (film and IBR, for example).  If you're in this situation
38   you'll be happy to know that Mesa supports 16-bit and 32-bit color
39   channels through the OSMesa interface.  When using 16-bit channels,
40   channels are GLushorts and RGBA pixels occupy 8 bytes.  When using 32-bit
41   channels, channels are GLfloats and RGBA pixels occupy 16 bytes.
42</p>
43<p>
44   To build Mesa/OSMesa with 16-bit color channels:
45<pre>
46      cd Mesa-5.x/src
47      make -f Makefile.X11 clean
48      make -f Makefile.OSMesa16 linux-osmesa16
49</pre>
50
51   For 32-bit channels:
52<pre>
53      cd Mesa-5.x/src
54      make -f Makefile.X11 clean
55      make -f Makefile.OSMesa16 linux-osmesa32
56</pre>
57
58<p>
59You'll wind up with a library named libOSMesa16.so or libOSMesa32.so.
60</p>
61
62<p>
63If you're not using Linux, you can easily edit Make-config and add
64an appropriate configuration.
65</p>
66<p>
67The Mesa/tests/osdemo16.c file (available via CVS) demonstrates how
68to use this feature.
69</p>
70<p>
71BE WARNED: 16 and 32-bit channel support has not been exhaustively
72tested and there may be some bugs.  However, a number of people have
73been using this feature successfully so it can't be too broken.
74</p>
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