说明：  ACIS是一个完整的modeling的内核，说白了就是一套用C++写的modeling类库，只要你掌握了这个库就可以完成所有的建模工作(基本上所有3D造型软件的功能他都有)，但是这个库的易用性不够，所以在其上又开发了一些API进一步对底层的acis类库进行封装
(ACIS is a complete modeling of the core, bluntly, is a set of C++, written in modeling library, as long as you have mastered this library can do all of the modeling work (basically all the functions of 3D modeling software, he has ), but the ease of use of this library is not enough, so they developed a number on it further to the underlying API encapsulation library acis)