VS2012下基于Glut 绘制矩形管示例程序：

使用GL_QUADS来绘制一个矩形空心管，其中用到了glFrontFace函数。可以按键盘UP,DOWN,LEFT,RIGHT按键旋转坐标系查看3D图形。也可以通过鼠标单击右键弹出的菜单选择正交和透视投影以及是否显示坐标轴。

void glFrontFace(GLenum mode);

作用是控制多边形的正面是如何决定的。在默认情况下，mode是GL_CCW。

mode的值为：

GL_CCW 表示窗口坐标上投影多边形的顶点顺序为逆时针方向的表面为正面。

GL_CW 表示顶点顺序为顺时针方向的表面为正面。

顶点的方向又称为环绕。

源代码：

// GlutPipeDemo.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;
//最大的投影矩阵堆栈深度
GLint iMaxProjectionStackDepth;
//最大的模型视图矩阵堆栈深度
GLint iMaxModeviewStackDepth;
//最大的纹理矩阵堆栈深度
GLint iMaxTextureStackDepth;
GLint iCoordinateaxis=1;
GLint iProjectionMode=1;
void changSize(GLint w,GLint h);
//菜单回调函数
void processMenu(int value){
	switch(value){
		case 1:
			iCoordinateaxis=1;
			break;
		case 2:
			iCoordinateaxis=2;
			break;
		case 3:
			iProjectionMode=1;
			//强制调用窗口大小变化回调函数，更改投影模式为正交投影
			changSize(glutGet(GLUT_WINDOW_WIDTH),glutGet(GLUT_WINDOW_HEIGHT));
			break;
		case 4:
			iProjectionMode=2;
			//强制调用窗口大小变化回调函数，更改投影模式为透视投影
			changSize(glutGet(GLUT_WINDOW_WIDTH),glutGet(GLUT_WINDOW_HEIGHT));
			break;
		default:
			break;
	}
	//重新绘制
	glutPostRedisplay();
}
//显示回调函数
void renderScreen(void){
	float fZ=100.0f,bZ=-100.0f;
	//将窗口颜色清理为黑色
	glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
    //把整个窗口清理为当前清理颜色：黑色；清除深度缓冲区。
    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);
	//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_BLEND);
	glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA);

	//白色绘制坐标系
	if(1==iCoordinateaxis){
		glColor3f(1.0f,1.0f,1.0f);
		glBegin(GL_LINES);
			glVertex3f(-90.0f,00.0f,0.0f);
			glVertex3f(90.0f,0.0f,0.0f);
			glVertex3f(0.0f,-90.0f,0.0f);
			glVertex3f(0.0f,90.0f,0.0f);
			glVertex3f(0.0f,0.0f,-90.0f);
			glVertex3f(0.0f,0.0f,90.0f);
		glEnd();

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

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

		glPushMatrix();
		glTranslatef(0.0f,0.0f,90.0f);
		glRotatef(70.0f,0.0f,0.0f,1.0f);
		glutSolidCone(3,6,10,10);
		glPopMatrix();
	}

	//Pipe外表面颜色
    glColor3ub(128, 128, 255);
    // Front Face ///////////////////////////////////
    glBegin(GL_QUADS);
		//多边形逆时针为正面
        // Pointing straight out Z
        glNormal3f(0.0f, 0.0f, 1.0f);	

        //上底面靠左的矩形
        glVertex3f(-50.0f, 50.0f, fZ);
        glVertex3f(-50.0f, -50.0f, fZ);
        glVertex3f(-35.0f, -50.0f, fZ);
        glVertex3f(-35.0f,50.0f,fZ);

        //上底面靠右的矩形
        glVertex3f(50.0f, 50.0f, fZ);
        glVertex3f(35.0f, 50.0f, fZ);
        glVertex3f(35.0f, -50.0f, fZ);
        glVertex3f(50.0f,-50.0f,fZ);

        //上底面靠上的矩形
        glVertex3f(-35.0f, 50.0f, fZ);
        glVertex3f(-35.0f, 35.0f, fZ);
        glVertex3f(35.0f, 35.0f, fZ);
        glVertex3f(35.0f, 50.0f,fZ);

        //上底面靠下的矩形
        glVertex3f(-35.0f, -35.0f, fZ);
        glVertex3f(-35.0f, -50.0f, fZ);
        glVertex3f(35.0f, -50.0f, fZ);
        glVertex3f(35.0f, -35.0f,fZ);

        // Top length section ////////////////////////////
        // Normal points up Y axis　
		//外侧上侧面
        glNormal3f(0.0f, 1.0f, 0.0f);
        glVertex3f(-50.0f, 50.0f, fZ);
        glVertex3f(50.0f, 50.0f, fZ);
        glVertex3f(50.0f, 50.0f, bZ);
        glVertex3f(-50.0f,50.0f,bZ);
		
        //外侧底侧面
        glNormal3f(0.0f, -1.0f, 0.0f);
        glVertex3f(-50.0f, -50.0f, fZ);
        glVertex3f(-50.0f, -50.0f, bZ);
        glVertex3f(50.0f, -50.0f, bZ);
        glVertex3f(50.0f, -50.0f, fZ);

        //外侧右侧面
        glNormal3f(1.0f, 0.0f, 0.0f);
        glVertex3f(50.0f, 50.0f, fZ);
        glVertex3f(50.0f, -50.0f, fZ);
        glVertex3f(50.0f, -50.0f, bZ);
        glVertex3f(50.0f, 50.0f, bZ);

        //外侧左侧面
        glNormal3f(-1.0f, 0.0f, 0.0f);
        glVertex3f(-50.0f, 50.0f, fZ);
        glVertex3f(-50.0f, 50.0f, bZ);
        glVertex3f(-50.0f, -50.0f, bZ);
        glVertex3f(-50.0f, -50.0f, fZ);
    glEnd();

	//多边形顺时针为正面
    glFrontFace(GL_CW);
    glBegin(GL_QUADS);
        // Back section
        // Pointing straight out Z
        glNormal3f(0.0f, 0.0f, -1.0f);	

        //下底面靠左的矩形
        glVertex3f(-50.0f, 50.0f, bZ);
        glVertex3f(-50.0f, -50.0f, bZ);
        glVertex3f(-35.0f, -50.0f, bZ);
        glVertex3f(-35.0f,50.0f,bZ);

        //下底面靠右的矩形
        glVertex3f(50.0f, 50.0f, bZ);
        glVertex3f(35.0f, 50.0f, bZ);
        glVertex3f(35.0f, -50.0f, bZ);
        glVertex3f(50.0f,-50.0f,bZ);

        //下底面靠上的矩形
        glVertex3f(-35.0f, 50.0f, bZ);
        glVertex3f(-35.0f, 35.0f, bZ);
        glVertex3f(35.0f, 35.0f, bZ);
        glVertex3f(35.0f, 50.0f,bZ);

        //下底面靠下的矩形
        glVertex3f(-35.0f, -35.0f, bZ);
        glVertex3f(-35.0f, -50.0f, bZ);
        glVertex3f(35.0f, -50.0f, bZ);
        glVertex3f(35.0f, -35.0f,bZ);
	
        // Insides /////////////////////////////
    	glColor3f(0.75f, 0.75f, 0.75f);
		
        // Normal points up Y axis
        glNormal3f(0.0f, 1.0f, 0.0f);
        glVertex3f(-35.0f, 35.0f, fZ);
        glVertex3f(35.0f, 35.0f, fZ);
        glVertex3f(35.0f, 35.0f, bZ);
        glVertex3f(-35.0f,35.0f,bZ);
        
        // Bottom section
        glNormal3f(0.0f, 1.0f, 0.0f);
        glVertex3f(-35.0f, -35.0f, fZ);
        glVertex3f(-35.0f, -35.0f, bZ);
        glVertex3f(35.0f, -35.0f, bZ);
        glVertex3f(35.0f, -35.0f, fZ);

        // Left section
        glNormal3f(1.0f, 0.0f, 0.0f);
        glVertex3f(-35.0f, 35.0f, fZ);
        glVertex3f(-35.0f, 35.0f, bZ);
        glVertex3f(-35.0f, -35.0f, bZ);
        glVertex3f(-35.0f, -35.0f, fZ);

        // Right Section
        glNormal3f(-1.0f, 0.0f, 0.0f);
        glVertex3f(35.0f, 35.0f, fZ);
        glVertex3f(35.0f, -35.0f, fZ);
        glVertex3f(35.0f, -35.0f, bZ);
        glVertex3f(35.0f, 35.0f, bZ);
    glEnd();

    glFrontFace(GL_CCW);		// Counter clock-wise polygons face out

    //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){
	
	// Light values and coordinates
    GLfloat  whiteLight[] = { 0.45f, 0.45f, 0.45f, 1.0f };
    GLfloat  sourceLight[] = { 0.25f, 0.25f, 0.25f, 1.0f };
	GLfloat	 lightPos[] = { 0.0f, 80.0f, 0.0f, 0.0f };

	// Enable lighting
    glEnable(GL_LIGHTING);
    // Setup and enable light 0
    glLightModelfv(GL_LIGHT_MODEL_AMBIENT,whiteLight);
    glLightfv(GL_LIGHT0,GL_AMBIENT,sourceLight);
    glLightfv(GL_LIGHT0,GL_DIFFUSE,sourceLight);
    glLightfv(GL_LIGHT0,GL_POSITION,lightPos);
    glEnable(GL_LIGHT0);
    // Enable color tracking
    glEnable(GL_COLOR_MATERIAL);
    // Set Material properties to follow glColor values
    glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);
	
    glEnable(GL_DEPTH_TEST);	//使能深度测试
    glFrontFace(GL_CCW);		//多边形正面为逆时针方向
    glEnable(GL_CULL_FACE);		//不显示背面

    //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(1.0f,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);
	//获取最大的投影矩阵堆栈深度
	glGetIntegerv( GL_MAX_PROJECTION_STACK_DEPTH,&iMaxProjectionStackDepth);
	//获取最大的模型视图矩阵堆栈深度
	glGetIntegerv( GL_MAX_MODELVIEW_STACK_DEPTH,&iMaxModeviewStackDepth);
	//获取最大的纹理矩阵堆栈深度
	glGetIntegerv( GL_MAX_TEXTURE_STACK_DEPTH,&iMaxTextureStackDepth);
	printf("point size range:%f-%f\n",sizes[0],sizes[1]);
	printf("point step:%f\n",step);
	printf("iMaxProjectionStackDepth=%d\n",iMaxProjectionStackDepth);
	printf("iMaxModeviewStackDepth=%d\n",iMaxModeviewStackDepth);
	printf("iMaxTextureStackDepth=%d\n",iMaxTextureStackDepth);
}
//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=120.0f;
    //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(1==iProjectionMode){
		printf("glOrtho\n");
		if(w<h)
			glOrtho(-coordinatesize,coordinatesize,-coordinatesize/ratio,coordinatesize/ratio,-coordinatesize*2.0f,coordinatesize*2.0f);
		else
			glOrtho(-coordinatesize*ratio,coordinatesize*ratio,-coordinatesize,coordinatesize,-coordinatesize*2.0f,coordinatesize*2.0f);
		//当前矩阵设置为模型视图矩阵
		glMatrixMode(GL_MODELVIEW);
		//重置当前指定的矩阵为单位矩阵　
		glLoadIdentity();
	}
	else{
		printf("gluPerspective\n");
		gluPerspective(45,ratio,10.0f,500.0f);
		//当前矩阵设置为模型视图矩阵
		glMatrixMode(GL_MODELVIEW);
		//重置当前指定的矩阵为单位矩阵　
		glLoadIdentity();
		glTranslatef(0.0f, 0.0f, -250.0f);
	}

}

//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[])
{
	GLint iMainMenu;
	GLint iCoordinateaxisMenu;
	GLint iOrthoOrPerspectMenu;
	//初始化glut 
    glutInit(&argc,argv);
    //使用双缓冲区、深度缓冲区。
    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 Pipe Demo
    glutCreateWindow("OpenGL Pipe 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);
	//菜单回调函数
	iCoordinateaxisMenu=glutCreateMenu(processMenu);
	//添加菜单
	glutAddMenuEntry("Display coordinate axis",1);
	glutAddMenuEntry("Don't dispaly coordinate axis",2);
	iOrthoOrPerspectMenu=glutCreateMenu(processMenu);
	glutAddMenuEntry("Ortho",3);
	glutAddMenuEntry("Perspect",4);
	iMainMenu=glutCreateMenu(processMenu);
	glutAddSubMenu("Display or hide coordinate axis",iCoordinateaxisMenu);
	glutAddSubMenu("Ortho Or Perspect",iOrthoOrPerspectMenu);
	//将菜单榜定到鼠标右键上
	glutAttachMenu(GLUT_RIGHT_BUTTON);
    //设置全局渲染参数
    setupRederingState();
    glutMainLoop();
    return 0;
}