OPENGL中构建天空和地面的例子，可以学习来构建虚拟环境等-OPENGL example of building in the sky and the ground

通过加载了地形的图片和天空，构造了一个场景，同时用opengl模拟了一个camera，可以前进、后退、左移、右移，然后鼠标可以控制。-By loading the topographic images and the sky, to construct a scene, at the same time using the OpenGL simulation of a camera, can move forward, backward, left, right, and then the mo