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Rev	Author	Line No.	Line
5098	clevermous	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.

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