DEM（二维）三维地形漫游系统:采用MFC和OPENGL利用分层设色制作,包括2D,3D的全部漫游功能,包括视点控制,飞行路线等交互操作 DEM (two-dimensional) three-dimensional terrain walkthrough system: using MFC and the use of layering colors OPENGL production, including 2D, 3D full roaming functionality, includi