说明：  <三维坐标系和几何学>介绍在使用“Direct3D立即模式”开发3d图形 程序时必须掌握的3d坐标的几何概念---DirectX 3D的左手坐标系。
(<Three-dimensional coordinate system and geometry> introduced in the use of Direct3D immediate mode 3d graphics development process must master the concept of 3d coordinates--- DirectX 3D geometry of the left-handed coordinate system.)