用openGL实现从三维点到屏幕坐标的映射，以达到拾取三维点的目的，可以精确的选中三维世界中的物体。tools文件下，包含常用的类代码，可以借鉴；目前包括获取windows下精确的时间；处理三维数据的vector类；-With openGL realize the mapping　three points to screen coordinates, pick up three points in order to achieve the purpose, you can　the precise three-dimensional objects in the world. Under tools file containing commonly used classes of code, you can learn　now includes access to windows at the precise time　handle three-dimensional vector class data