国家自然科学基金项目61379106,61379082,61227802;山东省自然科学基金项目ZR2013FM036,ZR2015FM011;浙江大学CAD&CG重点实验室开放基金项目A1315.National Natural Science Foundation of China61379106,61379082,61227802;Natural Science Foundation of Shandong ProvinceZR2013FM036,ZR2015FM011;Open Project Program of the State Key Lab of CAD&CGA1315