VS2012下基于Glut OpenGL glEdgeFlag示例程序：

glEdgeFlag (GLboolean flag)表示一个顶点是否应该被认为是多边形的一条边界边的起点。flag为GL_TRUE后面的点都被认为是边界上的点，flag为GL_FALSE则之后的点不是边界上的点。

Demo使用菜单来决定四角星的四个凹进去的点是否是边界边的起点。当菜单选中凹进去的四个点为边界上的点时，使用多边形的填充模式为GL_LINE时如下图所示：

当菜单选中凹进去的四个点不为边界上的点时，使用多边形的填充模式为GL_LINE时如下图所示：

源代码如下所示：

#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;
#define MODE_SOLID 1
#define MODE_LINE 2
#define MODE_POINTS 3
GLint iMode=MODE_SOLID;// 多边形的填充方式
GLboolean bEdgeFlag=GL_TRUE;//控制边的显示与否
//受支持的点大小范围
GLfloat sizes[2];
//受支持的点大小增量
GLfloat step;
//菜单回调函数
void processMenu(int value){
	switch(value){
		case 1:
			iMode=MODE_SOLID;
			break;
		case 2:
			iMode=MODE_LINE;
			break;
		case 3:
			iMode=MODE_POINTS;
			break;
		case 4:
			bEdgeFlag=GL_TRUE;
			break;
		case 5:
			bEdgeFlag=GL_FALSE;
			break;
		default:
			break;
	}
	//重新绘制
	glutPostRedisplay();
}
//显示回调函数
void renderScreen(void){
    GLfloat x,y,z,angle;
	int i;
    //把整个窗口清理为当前清理颜色：黑色
    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);
	//设置多边形正面和背面的填充模式
	if(MODE_SOLID==iMode)
		glPolygonMode(GL_FRONT_AND_BACK,GL_FILL);
	if(MODE_LINE==iMode)
		glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);
	if(MODE_POINTS==iMode)
		glPolygonMode(GL_FRONT_AND_BACK,GL_POINT);
	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
	if(MODE_POINTS!=iMode){
		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();
	}
	glColor3f(0.0f,1.0f,0.0f);
	glBegin(GL_TRIANGLES);
		//glPointSize(sizes[1]);
		glEdgeFlag(bEdgeFlag);
		glVertex2f(-20.0f, 20.0f);
		glEdgeFlag(GL_TRUE);
		glVertex2f(20.0f, 20.0f);
		glVertex2f(0.0f, 60.0f);
 
		glVertex2f(-20.0f,20.0f);
		glVertex2f(-60.0f,0.0f);
		glEdgeFlag(bEdgeFlag);
		glVertex2f(-20.0f,-20.0f);
		glEdgeFlag(GL_TRUE);
 
		glVertex2f(-20.0f,-20.0f);
		glVertex2f(0.0f, -60.0f);
		glEdgeFlag(bEdgeFlag);
		glVertex2f(20.0f, -20.0f);
		glEdgeFlag(GL_TRUE);
 
		glVertex2f(20.0f, -20.0f);
		glVertex2f(60.0f, 0.0f);
		glEdgeFlag(bEdgeFlag);
		glVertex2f(20.0f, 20.0f);
		glEdgeFlag(GL_TRUE);
 
		// Center square as two triangles
		glEdgeFlag(bEdgeFlag);
		glVertex2f(-20.0f, 20.0f);
		glVertex2f(-20.0f,-20.0f);
		glVertex2f(20.0f, 20.0f);
 
		glVertex2f(-20.0f,-20.0f);
		glVertex2f(20.0f, -20.0f);
		glVertex2f(20.0f, 20.0f);
		glEdgeFlag(GL_TRUE);
    glEnd();
 
    //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 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 Star Demo
    glutCreateWindow("OpenGL Star Demo");
	//创建二级菜单
	nModeMenu=glutCreateMenu(processMenu);
	glutAddMenuEntry("Solid",1);
	glutAddMenuEntry("Outline",2);
	glutAddMenuEntry("Points",3);
	nEdgeMenu=glutCreateMenu(processMenu);
	glutAddMenuEntry("On",4);
	glutAddMenuEntry("Off",5);
	nMainMenu=glutCreateMenu(processMenu);
	glutAddSubMenu("Mode",nModeMenu);
	glutAddSubMenu("Edge",nEdgeMenu);
	//将菜单榜定到鼠标右键上
	glutAttachMenu(GLUT_RIGHT_BUTTON);
    //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;
}