Review of Perceptual Tolerance to MotionTo Photon Latency

Review of Perceptual Tolerance to Motion-To. Photon Latency with Head Movement in Virtual Reality Presenter: Hyun Kyoon Lim (hlim@kriss. re. kr) Center for Medical Convergence Metrology Korea Research Institute of Standards and Science

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IEEE 3079 HMD Based VR Sickness Reducing Technology Dongil Dillon Seo, dillon. seo@telekom-capital. com Review of Perceptual Tolerance to Motion-To-Photon Latency with Head Movement in Virtual Reality Date: 2020 -02 -04 Author(s): Hyun Kyoon Lim Name Affiliation Hyun Kyoon Lim KRISS Sungshin Woman’s University Yonsei University KRISS Dong-A University Kyoung-Mi Jang Ye Shin Woo Dong. Hyun Lee Dong Soo Choi Phone [optional] 3079 -20 -0011 -00 -0000 -Review of Perceptual Tolerance to Motion-To-Photon Latency with Head Movement in Virtual Reality Email [optional] hlim@kriss. re. kr cest 20@gmail. com yeshin. woo@gmail. com ldh 1007@naver. com soochoi@dau. ac. kr 3

Reference: 3079 -20 -0011 -00 -0000 -Review of Perceptual Tolerance to Motion-To-Photon Latency with Head Movement in Virtual Reality 4

Abstract l Since MTP (Motion-To-Photon) latency is inevitable, it is necessary to quantify. l In this paper, 1) The effect of head movement on the threshold of MTP latency 2) To determine the acceptability of subjects for MTP latency above the threshold. l Three experiments were performed with different conditions (motion event, angle, angular velocity) • The above three influence the perception of MTP latency • Threshold for recognizing MTP latency varies according to angular velocity • MTP latency is more inconvenient in event-MTR than motion event-MSA 3079 -20 -0011 -00 -0000 -Review of Perceptual Tolerance to Motion-To-Photon Latency with Head Movement in Virtual Reality 5

Purpose l Perceptual sensitivity of MTP latency can be affected by head movements, including motion event, angle, angular velocity. Methods l MTP latency • To watch a video under head moving • The MTP latency of the system is measured to 28. 5 ms • The amount of add latency been loaded by the ring buffer • Added latency: 0, 11, 22, 33, 44, 66, 88 ms 3079 -20 -0011 -00 -0000 -Review of Perceptual Tolerance to Motion-To-Photon Latency with Head Movement in Virtual Reality 6

Methods l Head movement task • 2 motion events ① Motion-Static-Alternate (MSA): Abrupt change and movement in one direction ② Motion-To-Reverse (MTR): Instant motion in the opposite direction l 2 angles / 5 angular velocity conditions • 40 ° and 80 ° • 20, 40, 60, 80, Inf ° / s 3079 -20 -0011 -00 -0000 -Review of Perceptual Tolerance to Motion-To-Photon Latency with Head Movement in Virtual Reality 7

Methods l Experimental method on angle condition • MSA : (example) After staying at A for 2 sec, gently turn head 40°to B, and after staying at B for 2 sec, return to A. • MTR: (example) Go straight from B to A without staying 2 sec l Experimental method on angular velocity • MSA : (example) Stay at A for 2 sec, turn to B as quickly as possible. • MTR: (example) Go back to A-B-A without staying 2 sec 3079 -20 -0011 -00 -0000 -Review of Perceptual Tolerance to Motion-To-Photon Latency with Head Movement in Virtual Reality 8

Methods l Visual cueing • Red ~ blue dot : Guiding the beginning and end of the subject’s movement • Black dot : Guiding the subject to turn his head 3079 -20 -0011 -00 -0000 -Review of Perceptual Tolerance to Motion-To-Photon Latency with Head Movement in Virtual Reality 9

Materials l Video content • 5 contents : airplane, balloon, lion, studio, park – 4 k 360° l Subjects • Adult (age: 20’s) 19 (male : 11, female : 8) l Apparatus • HTC Vive head mounted display(HMD): resolution 2160 x 1200, 110° FOV, 90 Hz 3079 -20 -0011 -00 -0000 -Review of Perceptual Tolerance to Motion-To-Photon Latency with Head Movement in Virtual Reality 10

Result Ø Angles and Angular Velocities of Head Rotation 3079 -20 -0011 -00 -0000 -Review of Perceptual Tolerance to Motion-To-Photon Latency with Head Movement in Virtual Reality 11

Result Ø Perceptual Threshold of MTP Latency ü 5 -point scale: − 1 (imperceptible), 0 (uncertain), 1 (perceptible, but not annoying), 2 (annoying), 3 (very annoying) 3079 -20 -0011 -00 -0000 -Review of Perceptual Tolerance to Motion-To-Photon Latency with Head Movement in Virtual Reality 12

Result Ø The closer the color is to red, the higher the score Ø Mean opinion scores (MOS) are used to describe the central tendency. Ø The difference in MOS value changes slowly at first but then increases rapidly with increasing delay. Ø The maximum perceived threshold is 40. 70 ms at MSA, 80°and 20 °/ s Ø The minimum value is 22. 71 ms at MSA, 40 °, inf °/ s 3079 -20 -0011 -00 -0000 -Review of Perceptual Tolerance to Motion-To-Photon Latency with Head Movement in Virtual Reality 13

Result Ø Perceptual Threshold of MTP latency ü Threshold decreased in MTR than MSA § motion event, p = 0. 0022 <0. 05 ü Threshold decreases with increasing angular velocity • § In MSA: p = 0. 0003 <0. 05, § In MTR: p = 0: 0057 <0. 05 Total threshold plots against velocity : points are values of total thresholds curves are fitted model. 3079 -20 -0011 -00 -0000 -Review of Perceptual Tolerance to Motion-To-Photon Latency with Head Movement in Virtual Reality 14

Result Ø User Acceptance the over-threshold MTP latency • Normalized MOS versus added latency: points are measured MOS, curves are fitted logistic models 3079 -20 -0011 -00 -0000 -Review of Perceptual Tolerance to Motion-To-Photon Latency with Head Movement in Virtual Reality 15

Result Ø User Acceptance the over-threshold MTP latency • Normalized MOS versus added latency: points are measured MOS, curves are fitted logistic models 3079 -20 -0011 -00 -0000 -Review of Perceptual Tolerance to Motion-To-Photon Latency with Head Movement in Virtual Reality 16

Result Ø Simulator Sickness ü SSQ (Stimulator Sickness Questionnaires) before and after experiment 1) SSQ-Total score 2) SSQ-nausea 3) SSQ-oculomotor 4) SSQ-disorientation • The mean of SSQ scores with 95% CI 3079 -20 -0011 -00 -0000 -Review of Perceptual Tolerance to Motion-To-Photon Latency with Head Movement in Virtual Reality 17

Discussion l The symptoms of motion sickness worsen after the experiment. • But, the overall score is confirmed to be mild level. • Trials and rest periods within 20 minutes were thought to reduce the worsening of motion sickness. l Motion event : MTR < MSA ( all p <. 05 ) • Velocity (In MAS: p=. 0056 <. 05, In MTR: p=. 0214<. 05) • Angular velocity (In MAS: p=3. 7862 e-12 <. 05, In MTR: p=4. 1372 e-10<. 05) 3079 -20 -0011 -00 -0000 -Review of Perceptual Tolerance to Motion-To-Photon Latency with Head Movement in Virtual Reality 18

Thank you ! 19