Programming Concepts Chapter 3. The GL provides several categories of drawing subroutines for creating geometric figures, curves and surfaces, and character strings.
Some subroutines draw a complete figure while others are very basic and draw only a line or a point.
These subroutines draw primitive graphics figures, points, lines, and polygons, which are described as a set of vertices. These subroutines are primarily included for compatibility with existing GL programs. Setting Drawing Attributes Color, texture pattern, line style, and many others attributes affect all drawing subroutines. Unless you change an attribute before calling a drawing subroutine, the subroutine renders to the screen using the attributes currently set in the system. Setting Pipeline Options Turning optional pipeline tasks on and off speeds up the rendering process.