很简单的问题，但是惆怅了一天了

void display(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glPushMatrix();
gluLookAt(0.0,1.0,0.0,0.0,0.0,0.0,0.0,0.0,-1.0);
glMatrixMode(GL_MODELVIEW);
glColor3f(1.0,1.0,1.0);
//满天飞的淫荡的球~~
//glLoadIdentity();
glTranslatef(move_x_1,0.0,move_z_1);
glutSolidSphere(0.05,20,20);
glPopMatrix();
glFinish();
}
就这个鸟问题，
当我不用glLoadIdentity()，它可以在整个平面移动，但是当我用glLoadIdentity()后就只能沿着x轴移动了。为什么啊？？？？