VS2012下基于Glut OpenGL glScissor示例程序：

剪裁测试用于限制绘制区域。我们可以指定一个矩形的剪裁窗口，当启用剪裁测试后，只有在这个窗口之内的像素才能被绘制，其它像素则会被丢弃。换句话说，无论怎么绘制，剪裁窗口以外的像素将不会被修改。有的朋友可能玩过《魔兽争霸3》这款游戏。游戏时如果选中一个士兵，则画面下方的一个方框内就会出现该士兵的头像。为了保证该头像无论如何绘制都不会越界而覆盖到外面的像素，就可以使用剪裁测试。可以通过下面的代码来启用或禁用剪裁测试：

glEnable(GL_SCISSOR_TEST);   // 启用剪裁测试
glDisable(GL_SCISSOR_TEST); // 禁用剪裁测试

可以通过下面的代码来指定一个位置在(x, y)，宽度为width，高度为height的剪裁窗口。glScissor(x, y, width, height);注意，glScissor窗口坐标是以左下角为(0, 0)，右上角为(width, height)的，这与Windows系统窗口有所不同。

Demo使用裁剪区来将矩形窗口正中间四分之一刷成红色，正中间十六分之一刷成绿色。

源代码：

// GlutScissorDemo.cpp : 定义控制台应用程序的入口点。
//
#include "stdafx.h"
#include <gl/glut.h>
#include <math.h>
//圆周率宏
#define GL_PI 3.1415f
//获取屏幕的宽度
GLint SCREEN_WIDTH=0;
GLint SCREEN_HEIGHT=0;
//设置程序的窗口大小
GLint windowWidth=400;
GLint windowHeight=300;
//绕x轴旋转角度
GLfloat xRotAngle=0.0f;
//绕y轴旋转角度
GLfloat yRotAngle=0.0f;
//受支持的点大小范围
GLfloat sizes[2];
//受支持的点大小增量
GLfloat step;
//显示回调函数
void renderScreen(void){
    GLfloat x,y,z,angle;
	int i;
	// Clear blue window
	glClearColor(0.0f, 0.0f, 1.0f, 0.0f);
    //把整个窗口清理为当前清理颜色：蓝色
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
    //将当前Matrix状态入栈
    glPushMatrix();
    //坐标系绕x轴旋转xRotAngle
    glRotatef(xRotAngle,1.0f,0.0f,0.0f);
    //坐标系绕y轴旋转yRotAngle
    glRotatef(yRotAngle,0.0f,1.0f,0.0f);
	x=0.0f;
	y=0.0f;
    z=0.0f;
	//进行平滑处理　
	glEnable(GL_POINT_SMOOTH);
	glHint(GL_POINT_SMOOTH,GL_NICEST);
	glEnable(GL_LINE_SMOOTH);
	glHint(GL_LINE_SMOOTH,GL_NICEST);
	glEnable(GL_POLYGON_SMOOTH);
	glHint(GL_POLYGON_SMOOTH,GL_NICEST);
	//绘制坐标系
	glColor3f(1.0f,1.0f,1.0f);
	glBegin(GL_LINES);
		glVertex3f(-80.0f,0.0f,0.0f);
		glVertex3f(80.0f,0.0f,0.0f);
		glVertex3f(0.0f,-80.0f,0.0f);
		glVertex3f(0.0f,80.0f,0.0f);
		glVertex3f(0.0f,0.0f,-80.0f);
		glVertex3f(0.0f,0.0f,80.0f);
	glEnd();

	glPushMatrix();
	glTranslatef(80.0f,0.0f,0.0f);
	glRotatef(90.0f,0.0f,1.0f,0.0f);
	glutWireCone(3,6,10,10);
	glPopMatrix();

	glPushMatrix();
	glTranslatef(0.0f,80.0f,0.0f);
	glRotatef(-90.0f,1.0f,0.0f,0.0f);
	glutWireCone(3,6,10,10);
	glPopMatrix();

	glPushMatrix();
	glTranslatef(0.0f,0.0f,80.0f);
	glRotatef(90.0f,0.0f,0.0f,1.0f);
	glutWireCone(3,6,10,10);
	glPopMatrix();

    //使能裁剪区
	glEnable(GL_SCISSOR_TEST);
	//将窗口中间的四分之一面积清空为红色
    glClearColor(1.0f, 0.0f, 0.0f, 0.0f);
    glScissor(windowWidth/4,windowHeight/4, windowWidth/2,windowHeight/2);
    glClear(GL_COLOR_BUFFER_BIT);

    //将窗口中间的十六分之一面积清空为绿色
    glClearColor(0.0f, 1.0f, 0.0f, 0.0f);
    glScissor(windowWidth*3/8,windowHeight*3/8, windowWidth/4,windowHeight/4);
    glClear(GL_COLOR_BUFFER_BIT);

    //禁止裁剪区
    glDisable(GL_SCISSOR_TEST);

    //恢复压入栈的Matrix
    glPopMatrix();
    //交换两个缓冲区的指针
    glutSwapBuffers();
}
//设置Redering State
void setupRederingState(void){
    //设置清理颜色为黑色
    glClearColor(0.0f,0.0,0.0,1.0f);
    //设置绘画颜色为绿色
    glColor3f(0.0f,1.0f,0.0f);
	//使能深度测试
	glEnable(GL_DEPTH_TEST);
	//获取受支持的点大小范围
	glGetFloatv(GL_POINT_SIZE_RANGE,sizes);
	//获取受支持的点大小增量
	glGetFloatv(GL_POINT_SIZE_GRANULARITY,&step);
	printf("point size range:%f-%f\n",sizes[0],sizes[1]);
	printf("point step:%f\n",step);
}
//窗口大小变化回调函数
void changSize(GLint w,GLint h){
    //横宽比率
    GLfloat ratio;
    //设置坐标系为x(-100.0f,100.0f)、y(-100.0f,100.0f)、z(-100.0f,100.0f)
    GLfloat coordinatesize=100.0f;
    //窗口宽高为零直接返回
    if((w==0)||(h==0))
        return;
    //设置视口和窗口大小一致
    glViewport(0,0,w,h);
    //对投影矩阵应用随后的矩阵操作
    glMatrixMode(GL_PROJECTION);
    //重置当前指定的矩阵为单位矩阵　
    glLoadIdentity();
    ratio=(GLfloat)w/(GLfloat)h;
    //正交投影
    if(w<h)
        glOrtho(-coordinatesize,coordinatesize,-coordinatesize/ratio,coordinatesize/ratio,-coordinatesize,coordinatesize);
    else
        glOrtho(-coordinatesize*ratio,coordinatesize*ratio,-coordinatesize,coordinatesize,-coordinatesize,coordinatesize);
    //对模型视图矩阵堆栈应用随后的矩阵操作
    glMatrixMode(GL_MODELVIEW);
    //重置当前指定的矩阵为单位矩阵　
    glLoadIdentity();
}

//按键输入处理回调函数
void specialKey(int key,int x,int y){

    if(key==GLUT_KEY_UP){
        xRotAngle-=5.0f;
    }
    else if(key==GLUT_KEY_DOWN){
        xRotAngle+=5.0f;
    }
    else if(key==GLUT_KEY_LEFT){
        yRotAngle-=5.0f;
    }
    else if(key==GLUT_KEY_RIGHT){
        yRotAngle+=5.0f;
    }
    //重新绘制
    glutPostRedisplay();
}

int main(int argc, char* argv[])
{
    int nModeMenu;
	int nEdgeMenu;
	int nDepthMask;
	int nMainMenu;
	//初始化glut
    glutInit(&argc,argv);
    //使用双缓冲区模式
    glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGBA|GLUT_DEPTH);
    //获取系统的宽像素
    SCREEN_WIDTH=glutGet(GLUT_SCREEN_WIDTH);
    //获取系统的高像素
    SCREEN_HEIGHT=glutGet(GLUT_SCREEN_HEIGHT);
	//创建窗口，窗口名字为OpenGL Scissor Demo
    glutCreateWindow("OpenGL Scissor Demo");
    //设置窗口大小
    glutReshapeWindow(windowWidth,windowHeight);
    //窗口居中显示
    glutPositionWindow((SCREEN_WIDTH-windowWidth)/2,(SCREEN_HEIGHT-windowHeight)/2);
    //窗口大小变化时的处理函数
    glutReshapeFunc(changSize);
    //设置显示回调函数
    glutDisplayFunc(renderScreen);
    //设置按键输入处理回调函数
    glutSpecialFunc(specialKey);
    //设置全局渲染参数
    setupRederingState();
    glutMainLoop();
    return 0;
}