通过opengl函数实现地球，太阳，月球之间公转，自转，以及对于地球的纹理映射，并实现了太阳为点光源，地球和月球的阴影效果-Through the OpenGL function to achieve the earth, the sun, the moon s rotation, and between, to the earth texture mapping, and the realization of the sun as a point light source, the ear