FrictShoes: Providing Multilevel Nonuniform Friction Feedback on Shoes in VR. - Chih-An Tsao; Tzu-Chun Wu; Hsin-Ruey Tsai; Tzu-Yun Wei; Fang-Ying Liao; Sean Chapman; Bing-Yu Chen 004 (IEEE Trans. Vis. Comput. Graph., 2022)