初学OpenGL的程序（画球）

1. 利用Glut库，编写一个OpenGL程序，实现以下功能：

仿照课本2.4.3的例子，绘制若干OpenGL基本体素（三角形、三角形带、四边形、四边形带）构成的球体，
可以控制改变球的数量和球的体积，来改变基本体素的数量以及顶点的数量。
可以通过改变glPolygonMode，切换是否填充所绘制的基本体素。
用函数glutGet(GLUT_ELAPSED_TIME)（returns the time in milliseconds since

1	glutInit or the first invocation of the function）统计绘制时间

源程序如下：

#include<GL/glut.h>
#include<math.h>
#include<stdio.h>
#include<stdlib.h>
#include <iostream.h>
#define pi 3.1415926
#define GLfloat float
#define GLdouble double
#define GLint int
double c=pi/180.0;
double radius=150.0;
int w=500,h=500;
double angle=10.0;
double a=10.0;
void drawSphere(void)
{
    glViewport (0.0, 0.0, (GLsizei) w, (GLsizei) h);
    float theta,phir,phi,thetar,phir20
    ;
    float x,y,z;
    for(phi=-90.0;phi<=90.0;phi+=a)
    {
        phir=cphi;
        phir20=c(phi+a);
        glPolygonMode(GL_FRONT,GL_LINE);
        glPolygonMode(GL_BACK, GL_LINE);
    glFrontFace(GL_CCW); //逆时针为正面
    //glBegin(GL_TRIANGLES);
    //glBegin(GL_LINE_LOOP);
    glBegin(GL_TRIANGLE_STRIP);
    //glBegin(GL_TRIANGLE_FAN);
    //glBegin(GL_QUADS);
    //glBegin(GL_QUAD_STRIP);
    for(theta=-180.0;theta<=180.0;theta+=a)
    {
        thetar=ctheta;
        x=radiussin(thetar)cos(phir);
        y=radiuscos(thetar)cos(phir);
        z=radiussin(phir);
        glVertex3d(x,y,z);
    //glVertex3f(x,y,z);
        x=radiussin(thetar)cos(phir20);
        y=radiuscos(thetar)cos(phir20);
        z=radius*sin(phir20);
        glVertex3d(x,y,z);
    //glVertex3f(x,y,z);
    }
    glEnd();
}
glPolygonMode(GL_FRONT,GL_LINE);
glPolygonMode(GL_BACK, GL_LINE);
glFrontFace(GL_CCW);
    //glBegin(GL_QUADS);
    //glBegin(GL_QUAD_STRIP);
glBegin(GL_TRIANGLE_STRIP);
    //glBegin(GL_TRIANGLES);
    //glBegin(GL_TRIANGLE_FAN);
    //glBegin(GL_LINE_LOOP);
    //glBegin(GL_LINES);
    //glVertex3f(0.0,0.0,radius);
glVertex3d(0.0,0.0,radius);
double c80=c90.0;
z=radiussin(c80);
for(theta=-180.0;theta<=180.0;theta+=a)
{
    thetar=ctheta;
    x=radiussin(thetar)cos(c80);
    y=radiuscos(thetar)cos(c80);
    glVertex3d(x,y,z);
    //glVertex3f(x,y,z);
}
glEnd();
glPolygonMode(GL_FRONT,GL_LINE);
glPolygonMode(GL_BACK, GL_LINE);
glFrontFace(GL_CCW);
    //glBegin(GL_QUADS);
    //glBegin(GL_QUAD_STRIP);
glBegin(GL_TRIANGLE_STRIP);
    //glBegin(GL_TRIANGLES);
    //glBegin(GL_TRIANGLE_FAN);
    //glBegin(GL_LINE_LOOP);
    //glBegin(GL_LINES);
glVertex3d(0.0,0.0,-radius);
    //Vertex3f(0.0,0.0,-radius);
z=-radiussin(c80);
for(theta=-180.0;theta<=180.0;theta+=a)
{
    thetar=ctheta;
    x=radiussin(thetar)cos(c80);
    y=radiuscos(thetar)*cos(c80);
    glVertex3d(x,y,z);
    //lVertex3f(x,y,z);
}
glEnd();
glFlush();
glutSwapBuffers();
}
void reshape(GLsizei ww, GLsizei hh)
{
    glViewport (0, 0, (GLsizei) w, (GLsizei) h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0.0, (GLdouble)w,  0.0,(GLdouble)h, -w, h);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glViewport (0, 0, (GLsizei) w, (GLsizei) h);
    glClear(GL_COLOR_BUFFER_BIT);
    glFlush();
    w=ww;
    h=hh;
}
void init(void)
{
    glViewport(0,0,w,h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    //glOrtho(0.0, (GLdouble)w,  0.0,(GLdouble)h, -500, 500);
    glClearColor(0.0,0.0,0.0,0.0);
    glColor3f(0.0,1.0,0.0);
    glLoadIdentity();
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glClear(GL_COLOR_BUFFER_BIT);
    //glFlush();
}
void mouse(int btn,int state, int x,int y)
{
    //if(btn==GLUT_RIGHT_BUTTON &&state==GLUT_DOWN) exit(0);
    if(btn==GLUT_LEFT_BUTTON &&state==GLUT_DOWN)
    {
        radius=radius+15.0;
        drawSphere();
        printf("time is :%d\n",glutGet(GLUT_ELAPSED_TIME));
    }
}
static void idle(void)
{
    glutPostRedisplay();
}
void display(void)
{
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glClear (GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
    glTranslated(250,250,0);
    glRotated(30,1,0,0);
    glRotated(60,0,1,0);
    glRotated(90,0,0,1);
    angle = 12500.0/glutGet(GLUT_ELAPSED_TIME);
    glRotated(angle,1,0,0);
    glutPostRedisplay();
    drawSphere();
    printf("time is :%d\n",glutGet(GLUT_ELAPSED_TIME));
}
void submenu(int id)
{
    switch(id)
    {
        case 1:
        exit(0);
        break;
        case 2:
        radius=radius+10.0;
        break;
        case 3:
        if(radius>1.0) radius=radius/2;
        break;
    }
}
void main(int argc,char** argv)
{
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB);
    glutInitWindowSize(w,h);
    glutInitWindowPosition(0,0);
    glutCreateWindow("Swkkkk");
    glutCreateMenu(submenu);
    glutAddMenuEntry("quit",1);
    glutAddMenuEntry("Increase radius",2);
    glutAddMenuEntry("Decrease radius",3);
    glutAttachMenu(GLUT_RIGHT_BUTTON);
    init();
    glutMouseFunc(mouse);
    glutReshapeFunc(reshape);
    glutDisplayFunc(display);
    glEnable(GL_DEPTH_TEST);
    //glutIdleFunc(idle);
    glutMainLoop();
}