OpenGL,地球模型，纹理加载，虚拟跟踪球的实现-OpenGL, the Earth model, texture loading, the realization of a virtual tracking ball

实现空间坐标轴的显示，并通过鼠标进行交互，能实现身拖拽旋转，滚轮放大缩小，Opengl学习必备入门程序，并已封装好了各种类，方便学习-Realization of display space axes and interact with the mouse, drag the body to achieve rotation, zoom, Opengl learning essential entry procedures, and have a good package of various