OpenGL provides you with fairly direct control over the fundamental operations of two- and three-dimensional graphics. This includes specification of such parameters as transformation matrices, lighting equation coefficients, antialiasing methods, and pixel-update operators. However, it doesn't provide you with a means for describing or modeling complex geometric objects. Thus, the OpenGL commands you issue specify how a certain result should be produced (what procedure should be followed) rather than what exactly that result should look like. That is, OpenGL is fundamentally procedural rather than descriptive. To fully understand how to use OpenGL, it helps to know the order in which it carries out its operations.
OpenGL为您提供了对二维和三维图形的基本操作的相当直接的控制。这包括转换矩阵、光照方程系数、抗混叠方法和像素更新操作符等参数的指定。但是，它没有为您提供描述或建模复杂几何对象的方法。因此，您发出的OpenGL命令指定应该如何生成特定的结果(应该遵循什么过程)，而不是该结果应该是什么样子。也就是说，OpenGL本质上是程序性的，而不是描述性的。要完全理解如何使用OpenGL，了解它执行操作的顺序是有帮助的。
