从高程图（digital elevation map）读取地形高度数据，将地形数据组织成均匀三角网格，通过OpenGL绘制三维地形，并进行地形纹理贴图。同时要求实现地形的漫游，即可以前后左右移动视点来观察地形。-From the elevation map (digital elevation map) to read the terrain elevation data, terrain data will be organized into a uniform mesh, through t