程序代码：

#include <stdio.h>
#include <stdlib.h>
#include <GL/glut.h>
#include <time.h>
#include <math.h>

int winid;

float angx=-2.25,angxb=-13.5;
//float angx=0.0,angxb=-9.0;

void gears(float length,float lenadd,float parts) {
    float x,y,z,tmplen,i;
    float maxi=parts;
    glBegin(GL_LINE_LOOP);
    for (i=0.0;i<maxi;i+=1.0) {
        if ((int) i%2==0) {
            if ((int) (i/2)%2==0) {
                tmplen=length+8.0;
            } else {
                tmplen=length;
            }

        }
        x=(tmplen)*cos(6.28*i/maxi);
        y=(tmplen)*sin(6.28*i/maxi);
        glVertex3f(x,y,0.0);
    }
    glEnd();
}

void display(void) {
    float x,y,z;
    static float i,ti,tmplen;
    float maxi=40.0,length;
    glClear(GL_COLOR_BUFFER_BIT);
    glEnable(GL_BLEND);
    glEnable(GL_LINE_SMOOTH);
    glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA);
    glLineWidth(2.0);


    glPushMatrix();
    glRotatef(angx,0.0,0.0,1.0);
    gears(50.0,8.0,80.0);
    glPopMatrix();


    glPushMatrix();

    glTranslatef(-80.0,0.0,0.0);
    glRotatef(-angxb,0.0,0.0,1.0);
    gears(20.0,8.0,40.0);
    glPopMatrix();

    glFlush();
}

void idle(void) {
    angx+=2.0;
    angxb+=4.0;
    usleep(36000);
    glutPostRedisplay();
}

void reshape(int Width,int Height) {
    float far=200.0;
    glViewport(0,0,500,500);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(-100,100,-100,100,0,500);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt(0.0,0.0,far, 0.0,0.0,0.0, 0.0,1.0,far);
}

void init(void) {
    glClearColor(0.0,0.0,0.0,0.0);
}

void keypress(unsigned char key,int mousex,int mousey) {
    switch (key) {
    case 'q':
        glutDestroyWindow(winid);
        exit(0);
        break;
    case 'a':

        glutPostRedisplay();
        break;

    }
}

void keyup(unsigned char key,int mousex,int mousey) {
    switch (key) {
    case 'a':
        break;
    }
}

int main(int argc,char *argv[]) {
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_SINGLE|GLUT_RGBA);
    glutInitWindowSize(500,500);
    glutInitWindowPosition(100,100);
    winid=glutCreateWindow("Press x");
    init();
    glutReshapeFunc(reshape);
    glutDisplayFunc(display);
    glutIdleFunc(idle);
    glutKeyboardFunc(keypress);
    glutKeyboardUpFunc(keyup);
    glutMainLoop();
    return 0;
}