这是OPENGL初学者很好的一个学习例子。通过简单的平面图形绘制和变换画出一个笑脸，并以一定频率切换哭脸。内附opengl库。-This is an OPENGL a good learning example for beginners. Draw a simple planar graph and draw a smiley face change, and to a certain frequency switching crying face. Included opengl libra