void display (void)
{
    GLfloat gray[] = { 0.8, 0.8, 0.8, 1.0 };
    GLfloat black[] = { 0.0, 0.0, 0.0, 1.0 };

    glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glPushMatrix ();
    glTranslatef (0.0, 0.0, tdist);
    glRotatef ((GLfloat) spinx, 1.0, 0.0, 0.0);
    glRotatef ((GLfloat) spiny, 0.0, 1.0, 0.0);

    glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, gray);
    glMaterialfv(GL_FRONT, GL_SPECULAR, black);
    glMaterialf(GL_FRONT, GL_SHININESS, 0.0);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    glEnable(GL_POLYGON_OFFSET_FILL);//启用多边形偏移
    glPolygonOffset(polyfactor, polyunits);
    //计算偏移值
    glCallList (list);
    glDisable(GL_POLYGON_OFFSET_FILL);

    glDisable(GL_LIGHTING);
    glDisable(GL_LIGHT0);
    glColor3f (1.0, 1.0, 1.0);
    glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);//设置当前的多边形光栅化方法
    glCallList (list);
    glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);

    glPopMatrix ();
    glFlush ();
}