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  1. TinyGL 0.4 (c) 1997-2002 Fabrice Bellard.
  2.  
  3. General Description:
  4. --------------------
  5.  
  6. TinyGL is intended to be a very small implementation of a subset of
  7. OpenGL* for embedded systems or games. It is a software only
  8. implementation. Only the main OpenGL calls are implemented. All the
  9. calls I considered not important are simply *not implemented*.
  10.  
  11. The main strength of TinyGL is that it is fast and simple because it
  12. has not to be exactly compatible with OpenGL. In particular, the
  13. texture mapping and the geometrical transformations are very fast.
  14.  
  15. The main features of TinyGL are:
  16.  
  17. - Header compatible with OpenGL (the headers are adapted from the very good
  18. Mesa by Brian Paul et al.)
  19.  
  20. - Zlib-like licence for easy integration in commercial designs (read
  21. the LICENCE file).
  22.  
  23. - Subset of GLX for easy testing with X Window.
  24.  
  25. - GLX like API (NGLX) to use it with NanoX in MicroWindows/NanoX.
  26.  
  27. - Subset of BGLView under BeOS.
  28.  
  29. - OpenGL like lightening.
  30.  
  31. - Complete OpenGL selection mode handling for object picking.
  32.  
  33. - 16 bit Z buffer. 16/24/32 bit RGB rendering. High speed dithering to
  34. paletted 8 bits if needed. High speed conversion to 24 bit packed
  35. pixel or 32 bit RGBA if needed.
  36.  
  37. - Fast Gouraud shadding optimized for 16 bit RGB.
  38.  
  39. - Fast texture mapping capabilities, with perspective correction and
  40. texture objects.
  41.  
  42. - 32 bit float only arithmetic.
  43.  
  44. - Very small: compiled code size of about 40 kB on x86. The file
  45.   src/zfeatures.h can be used to remove some unused features from
  46.   TinyGL.
  47.  
  48. - C sources for GCC on 32/64 bit architectures. It has been tested
  49. succesfully on x86-Linux and sparc-Solaris.
  50.  
  51. Examples:
  52. ---------
  53.  
  54. I took three simple examples from the Mesa package to test the main
  55. functions of TinyGL. You can link them to either TinyGL, Mesa or any
  56. other OpenGL/GLX implementation. You can also compile them with
  57. Microwindows.
  58.  
  59. - texobj illustrates the use of texture objects. Its shows the speed
  60. of TinyGL in this case.
  61.  
  62. - glutmech comes from the GLUT packages. It is much bigger and slower
  63. because it uses the lightening. I have just included some GLU
  64. functions and suppressed the GLUT related code to make it work. It
  65. shows the display list handling of TinyGL in particular. You can look
  66. at the source code to learn the keys to move the robot. The key 't'
  67. toggles between shaded rendering and wire frame.
  68.  
  69. - You can download and compile the VReng project to see that TinyGL
  70. has been successfully used in a big project
  71. (http://www-inf.enst.fr/vreng).
  72.  
  73. Architecture:
  74. -------------
  75.  
  76. TinyGL is made up four main modules:
  77.  
  78. - Mathematical routines (zmath).
  79.  
  80. - OpenGL-like emulation (zgl).
  81.  
  82. - Z buffer and rasterisation (zbuffer).
  83.  
  84. - GLX interface (zglx).
  85.  
  86. To use TinyGL in an embedded system, you should look at the GLX layer
  87. and modify it to suit your need. Adding a more user friendly
  88. developper layer (as in Mesa) may be useful.
  89.  
  90. Notes - limitations:
  91. --------------------
  92.  
  93. - See the file 'LIMITATIONS' to see the current functions supported by the API.
  94.  
  95. - The multithreading could be easily implemented since no global state
  96. is maintainted. The library gets the current context with a function
  97. which can be modified.
  98.  
  99. - The lightening is not very fast. I supposed that in most games the
  100. lightening is computed by the 3D engine.
  101.  
  102. - Some changes are needed for 64 bit pointers for the handling of
  103. arrays of float with the GLParam union.
  104.  
  105. - List sharing is partialy supported in the source, but not by the
  106. current TinyGLX implementation (is it really useful ?).
  107.  
  108. - No user clipping planes are supported.
  109.  
  110. - No color index mode (no longer useful !)
  111.  
  112. - The mipmapping is not implemented.
  113.  
  114. - The perspecture correction in the mapping code does not use W but
  115. 1/Z. In any 'normal scene' it should work.
  116.  
  117. - The resizing of the viewport in TinyGLX ensures that the width and
  118. the height are multiples of 4. This is not optimal because some pixels
  119. of the window may not be refreshed.
  120.  
  121. Why ?
  122. -----
  123.  
  124. TinyGL was developped as a student project for a Virtual Reality
  125. network system called VReng (see the VReng home page at
  126. http://www-inf.enst.fr/vreng).
  127.  
  128. At that time (January 1997), my initial project was to write my own 3D
  129. rasterizer based on some old sources I wrote. But I realized that it
  130. would be better to use OpenGL to work on any platform. My problem was
  131. that I wanted to use texture mapping which was (and is still) quite
  132. slower on many software OpenGL implementation. I could have modified
  133. Mesa to suit my needs, but I really wanted to use my old sources for
  134. that project.
  135.  
  136. I finally decided to use the same syntax as OpenGL but with my own
  137. libraries, thinking that later it could ease the porting of VReng to
  138. OpenGL.
  139.  
  140. Now VReng is at last compatible with OpenGL, and I managed to patch
  141. TinyGL so that VReng can still work with it without any modifications.
  142.  
  143. Since TinyGL may be useful for some people, especially in the world of
  144. embedded designs, I decided to release it 'as is', otherwise, it would
  145. have been lost on my hard disk !
  146.  
  147. ------------------------------------------------------------------------------
  148. * OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
  149. ------------------------------------------------------------------------------
  150. Fabrice Bellard.
  151.