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