Hierarchical planning-based crowd formation: HPCF

The authors sincerely thank the referees and anonymous reviewers for their helpful comments and suggestions. This research was supported by the National Key Research and Development Program of China (2017YFB1002604, 2017YFB100-2600, and 2017YFB1402100), the National Key Cooperation between the BRICS of China (2017YFE0100500), and the Beijing Municipal Natural Science Foundation of China (4172033).