1. Beihang University, Beihang University, Qingdao Research Institute Qingdao, China
2. College of Computer Science and Engineering, Shandong University of Science and Technology, Qingdao, China
3. Beihang University, Qingdao Research Institute, Qingdao, China
4. State Key Laboratory of Virtual Reality and Technology, Beihang University, Beihang University, Qingdao Research Institute, Beijing, China