docs/osmesa.html

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  10 <h1>Off-screen Rendering</h1>
  11
  12
  13 <p>
  14 Mesa's off-screen rendering interface is used for rendering into
  15 user-allocated blocks of memory.
  16 That is, the GL_FRONT colorbuffer is actually a buffer in main memory,
  17 rather than a window on your display.
  18 There are no window system or operating system dependencies.
  19 One potential application is to use Mesa as an off-line, batch-style renderer.
  20 </p>
  21
  22 <p>
  23 The <b>OSMesa</b> API provides three basic functions for making off-screen
  24 renderings: OSMesaCreateContext(), OSMesaMakeCurrent(), and
  25 OSMesaDestroyContext().  See the Mesa/include/GL/osmesa.h header for
  26 more information about the API functions.
  27 </p>
  28
  29 <p>
  30 There are several examples of OSMesa in the <code>progs/osdemos/</code>
  31 directory.
  32 </p>
  33
  34
  35 <h2>Deep color channels</h2>
  36
  37 <p>
  38 For some applications 8-bit color channels don't have sufficient
  39 precision.
  40 OSMesa supports 16-bit and 32-bit color channels through the OSMesa interface.
  41 When using 16-bit channels, channels are GLushorts and RGBA pixels occupy
  42 8 bytes.
  43 When using 32-bit channels, channels are GLfloats and RGBA pixels occupy
  44 16 bytes.
  45 </p>
  46
  47 <p>
  48 Before version 6.5.1, Mesa had to be recompiled to support exactly
  49 one of 8, 16 or 32-bit channels.
  50 With Mesa 6.5.1, Mesa can be compiled for either 8, 16 or 32-bit channels
  51 and render into any of the smaller size channels.
  52 For example, if Mesa's compiled for 32-bit channels, you can also render
  53 16 and 8-bit channel images.
  54 </p>
  55
  56 <p>
  57 To build Mesa/OSMesa for 16 and 8-bit color channel support:
  58 <pre>
  59       make realclean
  60       make linux-osmesa16
  61 </pre>
  62
  63 <p>
  64 To build Mesa/OSMesa for 32, 16 and 8-bit color channel support:
  65 <pre>
  66       make realclean
  67       make linux-osmesa32
  68 </pre>
  69
  70 <p>
  71 You'll wind up with a library named libOSMesa16.so or libOSMesa32.so.
  72 Otherwise, most Mesa configurations build an 8-bit/channel libOSMesa.so library
  73 by default.
  74 </p>
  75
  76 <p>
  77 If performance is important, compile Mesa for the channel size you're
  78 most interested in.
  79 </p>
  80
  81 <p>
  82 If you need to compile on a non-Linux platform, copy Mesa/configs/linux-osmesa16
  83 to a new config file and edit it as needed.  Then, add the new config name to
  84 the top-level Makefile.  Send a patch to the Mesa developers too, if you're
  85 inclined.
  86 </p>
  87
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