本論文為減少VR使用者在虛擬實境體驗過程中產生不舒適而提出一項新的技術──材質模糊。許多VR使用者在遊玩過程中因各種緣故(如感知不匹配等)而容易產生動暈症等症狀，這使得VR內容設計者需要針對使用者舒適度調整VR內容設計，以減少使用者產生不舒適的機會。
本研究的實驗參與者人數為22人（16男6女），平均年齡24.4±2.6歲。所有實驗參與者皆執行6次實驗，實驗分成三種VR遊戲模式：直線行走(7.9 m/s)、直線行走(9.5 m/s)與自由移動(7.9 m/s)，分別探討三種遊戲模式下有無使用材質模糊的受試者感受差異。每次實驗時間約40分鐘，分為第一階段：VR遊戲實驗前靜坐休息（10分鐘）、第二階段：VR遊戲實驗中（15分鐘）以及第三階段：VR遊戲實驗後靜坐休息（10分鐘）。三階段均做心電圖量測，並在第一階段與第三階段請受試者填寫模擬器動暈問卷(SSQ)，第二階段則以每五分鐘為間隔口頭回答不舒適度分數。實驗結果分為主觀與客觀數據，主觀數據有口述不舒適度分數以及SSQ問卷的各項動暈症病症分類分數以及單項病症分數；客觀數據則為透過心電圖數據分析計得HRV生理訊號。
實驗結果顯示，三種不同VR遊戲模式在有使用材質模糊狀態下能使受試者在遊玩過程中產生較少的口述不舒適度分數。且在SSQ問卷研究結果顯示，有使用材質模糊狀態下動暈症症狀分數有較低於無使用材質模糊的趨勢。然而，在生理訊號HRV數據中則無法得到顯著的結果論述。

This thesis proposed a new technique, texture blur, to reduce the discomfort of VR users during the virtual reality experience. Due to various reasons such as perception mismatch, some VR users easily exhibit symptoms of cybersickness during the VR game. Therefore, VR content designers should adjust the VR content design to reduce the possibility of user discomfort.
Twenty-two participants were recruited in our experiment, 16 males and 6 females with an average age of 24.4±2.6 years. All participants performed 6 experiments, and there were three VR game modes: straight walking (7.9 m/s), straight walking (9.5 m/s) and free movement (7.9 m/s). The difference in severity of cybersickness between with and without texture blur condition were discussed separately in the three game modes. Each experiment took about 40 minutes and was divided into three sections. The first section: sit and rest before the VR game experiment (10 minutes), the second section: during the VR game experiment (15 minutes) and the third section: sit and rest after the VR game experiment (10 minute). The ECG measurement was performed in all three sections, and the subjects were asked to fill in the simulator sickness questionnaire (SSQ) in the first and third section. In the second section, subjects verbally answered the discomfort score every five minutes during the VR game. The subjective experimental result includes the verbally answered discomfort score, the SSQ scores of each classification of motion sickness and the 16 symptoms scores from SSQ. The objective experimental result is the HRV physiological signal calculated by ECG data analysis.
The result shows that the use of texture blur made subjects produced less verbally answered discomfort score during the three different VR game modes. And the SSQ results show that the symptoms scores of cybersickness in with texture blur condition was lower than without texture blur condition. However, in the HRV data of physiological signals, significant results cannot be obtained.

[1] Jerald, J. (2015). The VR book: Human-centered design for virtual reality. Morgan & Claypool.
[2] Bowins, B. (2010). Motion sickness: A negative reinforcement model. Brain research bulletin, 81(1), 7-11.
[3] Rebenitsch, L., & Owen, C. (2016). Review on cybersickness in applications and visual displays. Virtual Reality, 20(2), 101-125.
[4] Burdea, G. C., & Coiffet, P. (2003). Virtual reality technology. John Wiley & Sons
[5] Davis, S., Nesbitt, K., & Nalivaiko, E. (2014, December). A systematic review of cybersickness. In Proceedings of the 2014 Conference on Interactive Entertainment (pp. 1-9).
[6] Alger, M. (2015). Visual design methods for virtual reality. Ravensbourne. http://aperturesciencellc. com/vr/VisualDesignMethodsforVR_MikeAlger. pdf.
[7] Burns, E., Razzaque, S., Panter, A. T., Whitton, M. C., McCallus, M. R., & Brooks Jr, F. P. (2006). The hand is more easily fooled than the eye: Users are more sensitive to visual interpenetration than to visual-proprioceptive discrepancy. Presence: teleoperators & virtual environments, 15(1), 1-15.
[8] Samuel, A. J., Solomon, J., & Mohan, D. (2015). A critical review on the normal postural control. Physiotherapy and Occupational Therapy Journal, 8(2), 71.
[9] Stanney, K., Kennedy, R. and Drexler, J. 1997. Cybersickness is not simulator sickness. Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 41(2):1138-1142.
[10] Riccio, G. E., & Stoffregen, T. A. (1991). An ecological theory of motion sickness and postural instability. Ecological psychology, 3(3), 195-240.
[11] LaViola Jr, J. J. (2000). A discussion of cybersickness in virtual environments. ACM Sigchi Bulletin, 32(1), 47-56.
[12] Cobb, S., Nichols, S., Ramsey, A., and Wilson, J. Virtual reality-induced symptoms and effects (VRISE). 1999. Presence: Teleoperators and Virtual Environments, 8(2):169-186.
[13] Kolasinski, E. M. 1995. Simulator sickness in virtual environments. Technical Report. United States Army Research Institute for Behavioral and Social Sciences.
[14] Howarth, P . and Costello, P . 1997. The occurrence of virtual simulation sickness symptoms when an HMD was used as a personal viewing system. Displays, 18(2):107-116.
[15] Porcino, T. M., Clua, E., Trevisan, D., Vasconcelos, C. N., & Valente, L. (2017, April). Minimizing cyber sickness in head mounted display systems: design guidelines and applications. In 2017 IEEE 5th international conference on serious games and applications for health (SeGAH) (pp. 1-6). IEEE.
[16] McCauley, M. and Sharkey, T. 1992. Cybersickness: Perception of self-motion in virtual environments. Presence: Teleoperators and Virtual Environments, 1(3):311-318.
[17] Kramida, G. (2015). Resolving the vergence-accommodation conflict in head-mounted displays. IEEE transactions on visualization and computer graphics, 22(7), 1912-1931.
[18] Carnegie, K., & Rhee, T. (2015). Reducing visual discomfort with HMDs using dynamic depth of field. IEEE computer graphics and applications, 35(5), 34-41.
[19] Hillaire, S., Lécuyer, A., Cozot, R., & Casiez, G. (2008). Depth-of-field blur effects for first-person navigation in virtual environments. IEEE computer graphics and applications, 28(6), 47-55.
[20] Nie, G. Y., Duh, H. B. L., Liu, Y., & Wang, Y. (2019). Analysis on Mitigation of Visually Induced Motion Sickness by Applying Dynamical Blurring on a User's Retina. IEEE transactions on visualization and computer graphics.
[21] Kennedy, R. S., Lane, N., Berbaum, K. and Lilienthal, M. 1993. Simulator sickness questionnaire: An enhanced method for quantifying simulator sickness. The International Journal of Aviation Psychology, 3(3):203-220.
[22] Golding, J. F., & Markey, H. M. (1996). Effect of frequency of horizontal linear oscillation on motion sickness and somatogravic illusion. Aviation, space, and environmental medicine, 67(2), 121-126.
[23] Dennison, M. S., Wisti, A. Z., & D’Zmura, M. (2016). Use of physiological signals to predict cybersickness. Displays, 44, 42-52.
[24] Garcia, T. B. (2013). 12-lead ECG: The art of interpretation. Jones & Bartlett Publishers.
[25] McFee, R., & Parungao, A. (1961). An orthogonal lead system for clinical electrocardiography. American Heart Journal, 62(1), 93-100.
[26] van Ravenswaaij-Arts, C. M., Kollee, L. A., Hopman, J. C., Stoelinga, G. B., & van Geijn, H. P. (1993). Heart rate variability. Annals of internal medicine, 118(6), 436-447.
[27] Cornforth, D. J., Tarvainen, M. P., & Jelinek, H. F. (2014). How to calculate Renyi entropy from heart rate variability, and why it matters for detecting cardiac autonomic neuropathy. Frontiers in bioengineering and biotechnology, 2, 34.
[28] Camm, A. J., Malik, M., Bigger, J. T., Breithardt, G., Cerutti, S., Cohen, R. J., ... & Lombardi, F. (1996). Heart rate variability: standards of measurement, physiological interpretation and clinical use. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology.
[29] Guyton, A. C., & Hall, J. E. (1986). Textbook of medical physiology (Vol. 548). Philadelphia: Saunders.
[30] Kim, Y., Kim, H., Kim, E., Ko, H. and Kim, H. 2005. Characteristic changes in the physiological components of cybersickness. Psychophysiology, 42(5):616-625.
[31] Malińska, M., Zużewicz, K., Bugajska, J., & Grabowski, A. (2015). Heart rate variability (HRV) during virtual reality immersion. International Journal of Occupational Safety and Ergonomics, 21(1), 47-54.
[32] Ohyama, S., Nishiike, S., Watanabe, H., Matsuoka, K., Akizuki, H., Takeda, N., & Harada, T. (2007). Autonomic responses during motion sickness induced by virtual reality. Auris Nasus Larynx, 34(3), 303-306.
[33] Magaki, T., & Vallance, M. (2019, March). Developing an Accessible Evaluation Method of VR Cybersickness. In 2019 IEEE Conference on Virtual Reality and 3D User Interfaces (VR) (pp. 1072-1073). IEEE.
[34] Lin, Y. T., Chien, Y. Y., Wang, H. H., Lin, F. C., & Huang, Y. P. (2018, May). 65‐3: The Quantization of Cybersickness Level Using EEG and ECG for Virtual Reality Head‐Mounted Display. In SID Symposium Digest of Technical Papers (Vol. 49, No. 1, pp. 862-865).
[35] Alger, M. (2015). Visual design methods for virtual reality. Ravensbourne. http://aperturesciencellc. com/vr/VisualDesignMethodsforVR_MikeAlger. pdf.
[36] So, R. H., Lo, W. T., & Ho, A. T. (2001). Effects of navigation speed on motion sickness caused by an immersive virtual environment. Human factors, 43(3), 452-461.
[37] Bonato, F., Bubka, A., Palmisano, S., Phillip, D., & Moreno, G. (2008). Vection change exacerbates simulator sickness in virtual environments. Presence: Teleoperators and Virtual Environments, 17(3), 283-292.
[38] Chen, W., Plancoulaine, A., Férey, N., Touraine, D., Nelson, J., & Bourdot, P. (2013, October). 6DoF navigation in virtual worlds: comparison of joystick-based and head-controlled paradigms. In Proceedings of the 19th ACM Symposium on Virtual Reality Software and Technology (pp. 111-114).
[39] https://www.vive.com/tw/product/vive/
[40] https://www.tomorrowtech41.com/products/htc-vive-re
[41] Howarth, P. A., & Hodder, S. G. (2008). Characteristics of habituation to motion in a virtual environment. Displays, 29(2), 117-123.
[42] Dennison, M. S., Wisti, A. Z., & D’Zmura, M. (2016). Use of physiological signals to predict cybersickness. Displays, 44, 42-52.