1. a Interactive Virtual Reality Laboratory, School of Internet Media Engineering, Korea University of Technology and Education, Gajeonri 307, Byeong cheon-myeon, Cheon-an, Chungnam, South Korea
2. b Electronics and Telecommunication Research Institute, Gajeongno, Yuseung-gu, Daejeon, 305-700, South Korea
3. c Computer Graphics & Visualization Laboratory, School of Engineering, ICU, Munjiro 119, Yuseong-gu, Daejeon, 305-714, South Korea
4. d Telerobotics & Control Laboratory, Dept. of Mechanical Engineering, KAIST, Guseong-Dong 373-1, Yuseung-gu, Daejeon, 305-701, South Korea