docs/osmesa.html

   1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
   2 <html lang="en">
   3 <head>
   4   <meta http-equiv="content-type" content="text/html; charset=utf-8">
   5   <title>Off-screen Rendering</title>
   6   <link rel="stylesheet" type="text/css" href="mesa.css">
   7 </head>
   8 <body>
   9
  10 <div class="header">
  11   <h1>The Mesa 3D Graphics Library</h1>
  12 </div>
  13
  14 <iframe src="contents.html"></iframe>
  15 <div class="content">
  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 <code>progs/osdemos/</code>
  38 directory.
  39 </p>
  40
  41
  42 <h2>Deep color channels</h2>
  43
  44 <p>
  45 For some applications 8-bit color channels don't have sufficient
  46 precision.
  47 OSMesa supports 16-bit and 32-bit color channels through the OSMesa interface.
  48 When using 16-bit channels, channels are GLushorts and RGBA pixels occupy
  49 8 bytes.
  50 When using 32-bit channels, channels are GLfloats and RGBA pixels occupy
  51 16 bytes.
  52 </p>
  53
  54 <p>
  55 Before version 6.5.1, Mesa had to be recompiled to support exactly
  56 one of 8, 16 or 32-bit channels.
  57 With Mesa 6.5.1, Mesa can be compiled for either 8, 16 or 32-bit channels
  58 and render into any of the smaller size channels.
  59 For example, if Mesa's compiled for 32-bit channels, you can also render
  60 16 and 8-bit channel images.
  61 </p>
  62
  63 <p>
  64 To build Mesa/OSMesa for 16 and 8-bit color channel support:
  65 <pre>
  66       make realclean
  67       make linux-osmesa16
  68 </pre>
  69
  70 <p>
  71 To build Mesa/OSMesa for 32, 16 and 8-bit color channel support:
  72 <pre>
  73       make realclean
  74       make linux-osmesa32
  75 </pre>
  76
  77 <p>
  78 You'll wind up with a library named libOSMesa16.so or libOSMesa32.so.
  79 Otherwise, most Mesa configurations build an 8-bit/channel libOSMesa.so library
  80 by default.
  81 </p>
  82
  83 <p>
  84 If performance is important, compile Mesa for the channel size you're
  85 most interested in.
  86 </p>
  87
  88 <p>
  89 If you need to compile on a non-Linux platform, copy Mesa/configs/linux-osmesa16
  90 to a new config file and edit it as needed.  Then, add the new config name to
  91 the top-level Makefile.  Send a patch to the Mesa developers too, if you're
  92 inclined.
  93 </p>
  94
  95 </div>
  96 </body>
  97 </html>