投影变换

投影变换的目的就是确定可视空间。

投影变换分为两类，一个为透视投影，一个为正投影。

用于透视投影变换的函数有两个。

 

glFrustrum(GLdouble left,GLdouble right,GLdouble bottom,GLdouble top,GLdouble near,GLdouble far);

 

gluPerspective(GLdouble fovy,GLdouble aspect,GLdouble near,GLdouble far);

 

用于正投影的变换函数：

 

glOrtho((GLdouble left,GLdouble right,GLdouble bottom,GLdouble top,GLdouble near,GLdouble far);

glOrtho2D((GLdouble left,GLdouble right,GLdouble bottom,GLdouble top);