// 范例P96.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <gl/glut.h>

void display()
{
 glClear(GL_COLOR_BUFFER_BIT);     //清除所有像素
 glColor3f(1.0,1.0,1.0);       //设置画笔白色
 /*在缓存中绘制4对顶点坐标的矩形*/
 GLdouble eqn[4]={0.0,1.0,0.0,0.0};
 GLdouble eqn2[4]={1.0,0.0,0.0,0.0};
 GLdouble eqn3[4]={0.0,0.0,1.0,0};
 glPushMatrix();
 glTranslatef(0.0,0.0,-5.0);      //模型变换

 /*裁掉下半部分(y坐标小于0的部分)*/
 glClipPlane(GL_CLIP_PLANE0,eqn);    
 glEnable(GL_CLIP_PLANE0);

    /*裁掉左半部分(x坐标小于0的部分)*/
 glClipPlane(GL_CLIP_PLANE1,eqn2);
 glEnable(GL_CLIP_PLANE1);
 
 glRotatef(90.0,1.0,0.0,0.0);
 glutWireSphere(1.0,20,16);
 glPopMatrix();

 glFlush();          //立即显示出来
}

void init()
{
 glClearColor(0.0,0.0,0.0,0.0);     //用黑色清除背景
 glShadeModel(GL_FLAT);
}
void reshape(int w,int h)
{
 glViewport(0,0,(GLsizei)w,(GLsizei)h);
 glMatrixMode(GL_PROJECTION);
 glLoadIdentity();
 gluPerspective(30,(GLfloat)w/(GLfloat)h,0.1,20.0);
 glMatrixMode(GL_MODELVIEW);
}
int main(int argc,char ** argv)
{
 glutInit(&argc,argv);
 glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
 glutInitWindowSize(500,500);     //初始化窗口大小
 glutInitWindowPosition(100,100);    //初始化窗口位置
 glutCreateWindow("hello");      //创建标题为“hello”的窗口
 init();           //调用初始化函数
 glutDisplayFunc(display);      //注册回调函数
 glutReshapeFunc(reshape);
 glutMainLoop();         //进入主循环处理事件
 
 return 0;
}

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