点击物体，可以产生像3DMax那样产生轨迹球，通过点击各个圆并移动鼠标来旋转物体。-Click on objects, can produce as 3DMax produced as a trackball, by clicking on each circle and move the mouse to rotate the object.

这个例子综合了主源文件sphereworld.cpp之外，该项目还包括了来自\shared文件夹的gltools.cpp、,math3d.cpp、glframe.h-This case integrated to the main source file sphereworld.cpp The project also includes from \ shared file folder gltools.cpp math3d.cpp, glframe.h