使用OpenGL对三维模型进行切割，显示出切割面，鼠标双击模型上的某个地方，确定一个点，连续三次，确定三个点，从而确定一个平面，此平面会将模型切割，显示出切割面-The use of OpenGL for three-dimensional cutting model, showing that the cutting surface, double-click the mouse model of a place to identify a point three times in a row