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#include //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 3GLint 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