opengl小实例-地球公转和自转

此实例在opengl编程指南中有,这里具体说明一下

static int year= 0,day=0;

void Init()

{

    glClearColor(0.0,0.0,0.0,0.0);

    glShadeModel(GL_FLAT);

}

void reshape(int w,int h)

{

    glViewport(0,0,(GLsizei)w,(GLsizei)h);

    glMatrixMode(GL_PROJECTION);

    glLoadIdentity();

    gluPerspective(40,(GLfloat)w/(GLfloat)h,1,20);

    glMatrixMode(GL_MODELVIEW);

    glLoadIdentity();

    gluLookAt(0.0,0.0,5.0,0.0,0.0,0.0,0.0,1.0,0.0);  //以前犯过的一个错,把此句加载投影模式下了,怎么都看不到模型

                                                     //这个应该是模型视图变换

}

void keyboard(unsigned char key,int x,int y)

{

    switch (key) {

    case 'd':

        day = (day+10)/360;     //这边的360当然是一个圆周了

        glutPostRedisplay();

        break;

    case 'D':

        day = (day-10)%360;

        glutPostRedisplay();

        break;

    case 'y':

        year = (year+5)%360;

        glutPostRedisplay();

        break;

    case 'Y':

        year = (year-5)%360;

        glutPostRedisplay();

        break;

    default:

        break;

    }

}

void display()

{

    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

    glColor3f(1,1,1);

    glPushMatrix();

    glutWireSphere(1.0,22,16);

    glRotatef((GLfloat)year,0.0,1.0,0.0);

    glTranslatef(2.0,0.0,0.0);                     //公转和自传的区别,就是此句代码

    glRotatef((GLfloat)day,0.0,1.0,0.0);

    glutWireSphere(0.3,10,8);

    glPopMatrix();

    glutSwapBuffers();

}

int main(int argc,char** argv)

{

    glutInit(&argc,argv);

    glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGBA|GLUT_DEPTH);

    glutInitWindowSize(640,480);

    glutInitWindowPosition(100,100);

    glutCreateWindow("Maya Camera");

    Init();

    glutDisplayFunc(display);

    glutReshapeFunc(reshape);

    glutKeyboardFunc(keyboard);

    glutMainLoop();

    return 0;

}