OpenGL is a software interface to graphics hardware (the "GL" stands for Graphics Library). This interface consists of several hundred functions that allow graphics programmers to specify the objects and operations needed to produce high-quality color images of three-dimensional objects. Many of the functions are actually simple variations of each other, so in reality there are only about 180 substantially different functions. The OpenGL Utility Library (GLU) and the OpenGL Extension to the X Window System (GLX) provide useful supporting features and complement the core OpenGL set of functions. This manual explains what all these functions do. The following list summarizes the contents of each chapter.
* Chapter1, Introduction to OpenGL, provides a conceptual overview of OpenGL. It uses a high-level block diagram to explain all the major stages of processing OpenGL performs. * Chapter2, Overview of Commands and Routines, describes in more detail how OpenGL processes input data (in the form of vertices specifying a geometric object or of pixels defining an image) and how you can control this processing using OpenGL functions. GLU and GLX functions are also discussed. * Chapter3, Summary of Commands and Routines, lists the OpenGL commands in groups according to the tasks they perform. The full prototypes provided in this chapter allow you to use it as a quick reference once you understand what the commands accomplish. * Chapter4, Defined Constants and Associated Commands, lists the constants defined in OpenGL and the commands that use them. * Chapter5, OpenGL Reference Pages, which forms the bulk of this manual, contains reference pages describing each set of related OpenGL commands. Commands with parameters that differ only in data type are described together. Each reference page describes the parameters, the effect of the commands, and what errors might result from using the commands. Additionally, this section contains the reference pages for the OpenGL ARB extensions: multitexture and the imaging subset. Not all OpenGL implementations may include support for the ARB extensions. * Chapter6, GLU Reference Pages, contains reference pages for all GLU commands. * Chapter7, GLX Reference Pages, contains reference pages for all GLX commands.
What You Should Know Before Reading This Manual
This manual is intended as the companion reference volume to the OpenGL Programming Guide, Third Edition, by Mason Woo, Jackie Neider, Tom Davis, and Dave Shreiner (Reading, MA: Addison-Wesley, 1999). Both books assume that you know how to program in C.
While the focus of the OpenGL Programming Guide is on how to use OpenGL, the focus of this reference manual is on how OpenGL works. For a complete understanding of OpenGL, you need both types of information. Another difference between the two books is that most of the content of this manual is organized alphabetically, based on the assumption that you know what you don't know and therefore need only to look up a description of a particular command. The OpenGL Programming Guide is organized like a tutorial: it explains the simpler OpenGL concepts first and builds up to the more complex ones. Although you don't have to read the OpenGL Programming Guide to understand the command descriptions in this manual, your understanding of their intended use will be much more complete if you have read it.
If you don't know much about computer graphics, start with the programming guide rather than this reference manual. In addition, consider these books.
* Computer Graphics: Principles and Practice by James D. Foley, Andries van Dam, Steven K. Feiner, and John F. Hughes (Reading, MA: Addison-Wesley Publishing Company)--This book is an encyclopedic treatment of the subject of computer graphics. It includes a wealth of information but is probably best read after you have some experience with the subject. * 3D Computer Graphics: A User's Guide for Artists and Designers by Andrew S. Glassner (New York: Design Press)--This book is a nontechnical, gentle introduction to computer graphics. It focuses on the visual effects that can be achieved rather than on the techniques needed to achieve them. * The Way Computer Graphics Work by Olin Lathrop (New York: John Wiley and Sons, Inc.)--This book is a general introduction to computer graphics directed at the beginner to intermediate level computer users. It describes the general principles required for understanding computer graphics.
Style Conventions
This guide uses the following style conventions:
* Bold--Command and routine names * Italics--Variables, arguments, parameter names, spatial dimensions, and document names * Regular--Enumerated types and defined constants * Monospace font--Code examples
Note that this manual uses abbreviations for command names. Many OpenGL commands are just variations of each other. For simplicity, only the base name of the command is used, and an asterisk is included to indicate that there may be more to the actual command name than is being shown. For example, glVertex* stands for all variations of the command available to specify vertices.
The commands differ mostly in the data type of arguments. Some commands differ in the number of related arguments and whether those arguments can be specified as a vector or whether they must be specified separately in a list. For example, if you use the glVertex2f command, you must supply x and y coordinates as floating-point numbers; with glVertex3sv, you must supply an array of three short integer values for x, y, and z.
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