其函數(shù)原型為：glViewport(GLint x,GLint y,GLsizei width,GLsizei height)x，y 以像素為單位，指定了視口的左下角位置。width，height 表示這個(gè)視口矩形的寬度和高度，根據(jù)窗口的實(shí)時(shí)變化重繪窗口。
在默認(rèn)情況下，視口被設(shè)置為占據(jù)打開窗口的整個(gè)像素矩形，窗口大小和設(shè)置視口大小相同，所以為了選擇一個(gè)更小的繪圖區(qū)域，就可以用glViewport函數(shù)來實(shí)現(xiàn)這一變換，在窗口中定義一個(gè)像素矩形，最終將圖像映射到這個(gè)矩形中。例如可以對(duì)窗口區(qū)域進(jìn)行劃分，在同一個(gè)窗口中顯示分割屏幕的效果，以顯示多個(gè)視圖。

#include?"stdafx.h"
#include#define?GLUT_DISABLE_ATEXIT_HACK
#include?"gl/glut.h"

void?myDisplay()
{
?glClear(GL_COLOR_BUFFER_BIT);
?glColor3f(1.0,?0.0,?0.0);
?//畫分割線，分成四個(gè)視區(qū)??
?glViewport(0,?0,?400,?400);
?glBegin(GL_LINES);
?glVertex2f(-1.0,?0);
?glVertex2f(1.0,?0);
?glVertex2f(0.0,?-1.0);
?glVertex2f(0.0,?1.0);
?glEnd();
?
?//定義在左下角的區(qū)域??
?glColor3f(0.0,?1.0,?0.0);
?glViewport(0,?0,?200,?200);
?glBegin(GL_POLYGON);
?glVertex2f(-0.5,?-0.5);
?glVertex2f(-0.5,?0.5);
?glVertex2f(0.5,?0.5);
?glVertex2f(0.5,?-0.5);
?glEnd();

?//定義在右上角的區(qū)域??
?glColor3f(0.0,?0.0,?1.0);
?glViewport(200,?200,?200,?200);//注意，后面這兩個(gè)參數(shù)是高度和寬度，而不是坐標(biāo)??
?glBegin(GL_POLYGON);
?glVertex2f(-0.5,?-0.5);
?glVertex2f(-0.5,?0.5);
?glVertex2f(0.5,?0.5);
?glVertex2f(0.5,?-0.5);
?glEnd();

?//定義在左上角的區(qū)域??
?glColor3f(1.0,?0.0,?0.0);
?glViewport(0,?200,?200,?200);??
?glBegin(GL_POLYGON);
?glVertex2f(-0.5,?-0.5);
?glVertex2f(-0.5,?0.5);
?glVertex2f(0.5,?0.5);
?glVertex2f(0.5,?-0.5);
?glEnd();
?
?//定義在右下角??
?glColor3f(1.0,?1.0,?1.0);
?glViewport(200,?0,?200,?200);
?glBegin(GL_POLYGON);
?glVertex2f(-0.5,?-0.5);
?glVertex2f(-0.5,?0.5);
?glVertex2f(0.5,?0.5);
?glVertex2f(0.5,?-0.5);
?glEnd();
?glFlush();
?}

int?main(int?argc,?char?*argv[])
{
?glutInit(&argc,?argv);
?glutInitDisplayMode(GLUT_RGB?|?GLUT_SINGLE);
?glutInitWindowPosition(100,?100);
?glutInitWindowSize(400,?400);
?glutCreateWindow("第一個(gè)OpenGL程序");
?glutDisplayFunc(&myDisplay);
?glutMainLoop();
?return?0;
}