def redraw():
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    glPushMatrix()
    glRotatef(angle_x, 1, 0, 0);
    glRotatef(angle_y, 0, 0, 1);
    glCallList(DISPLAY_LIST)
    glPopMatrix()
    glutSwapBuffers()