docs/osmesa.html

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  10 <div class="header">
  11   <h1>The Mesa 3D Graphics Library</h1>
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  16
  17 <h1>Off-screen Rendering</h1>
  18
  19
  20 <p>
  21 Mesa's off-screen rendering interface is used for rendering into
  22 user-allocated blocks of memory.
  23 That is, the GL_FRONT colorbuffer is actually a buffer in main memory,
  24 rather than a window on your display.
  25 There are no window system or operating system dependencies.
  26 One potential application is to use Mesa as an off-line, batch-style renderer.
  27 </p>
  28
  29 <p>
  30 The <b>OSMesa</b> API provides three basic functions for making off-screen
  31 renderings: OSMesaCreateContext(), OSMesaMakeCurrent(), and
  32 OSMesaDestroyContext().  See the Mesa/include/GL/osmesa.h header for
  33 more information about the API functions.
  34 </p>
  35
  36 <p>
  37 There are several examples of OSMesa in the mesa/demos repository.
  38 </p>
  39
  40
  41 <h2>Deep color channels</h2>
  42
  43 <p>
  44 For some applications 8-bit color channels don't have sufficient
  45 precision.
  46 OSMesa supports 16-bit and 32-bit color channels through the OSMesa interface.
  47 When using 16-bit channels, channels are GLushorts and RGBA pixels occupy
  48 8 bytes.
  49 When using 32-bit channels, channels are GLfloats and RGBA pixels occupy
  50 16 bytes.
  51 </p>
  52
  53 <p>
  54 Before version 6.5.1, Mesa had to be recompiled to support exactly
  55 one of 8, 16 or 32-bit channels.
  56 With Mesa 6.5.1, Mesa can be compiled for either 8, 16 or 32-bit channels
  57 and render into any of the smaller size channels.
  58 For example, if Mesa's compiled for 32-bit channels, you can also render
  59 16 and 8-bit channel images.
  60 </p>
  61
  62 <p>
  63 To build Mesa/OSMesa for 16 and 8-bit color channel support:
  64 <pre>
  65       make realclean
  66       make linux-osmesa16
  67 </pre>
  68
  69 <p>
  70 To build Mesa/OSMesa for 32, 16 and 8-bit color channel support:
  71 <pre>
  72       make realclean
  73       make linux-osmesa32
  74 </pre>
  75
  76 <p>
  77 You'll wind up with a library named libOSMesa16.so or libOSMesa32.so.
  78 Otherwise, most Mesa configurations build an 8-bit/channel libOSMesa.so library
  79 by default.
  80 </p>
  81
  82 <p>
  83 If performance is important, compile Mesa for the channel size you're
  84 most interested in.
  85 </p>
  86
  87 <p>
  88 If you need to compile on a non-Linux platform, copy Mesa/configs/linux-osmesa16
  89 to a new config file and edit it as needed.  Then, add the new config name to
  90 the top-level Makefile.  Send a patch to the Mesa developers too, if you're
  91 inclined.
  92 </p>
  93
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