https://blog.gongquiz.com/2021/04/20/csg-%eb%aa%a8%eb%8d%b8%eb%a7%81-%eb%b0%a9%ec%8b%9d%ec%97%90%ec%84%9c-%eb%b3%bc-%ec%97%b0%ec%82%b0boolean-operation%ec%9d%b4-%ec%95%84%eb%8b%8c-%ea%b2%83%ec%9d%80-%ea%b8%b0%ea%b3%84%ec%84%a4/