Dynamically Adjusted and Peripheral Visualization of Reverse Optical Flow for VR Sickness Reduction

Round 1

Reviewer 1 Report

The author proposed a study on adjusted and peripheral visualization. The idea is quite interesting, however there are some drawbacks in the manuscript:

1. Abstract should free from citation , author should revise the abstract and remove any citation or reference. Author can move that citation to introduction section.

2. I suggest author to add user testing picture during the four-condition testing (refer to Figure 3)

3. Author mention that more than 41 users recruited using online questionnaire? how author manage the different skills of user toward VR application? user with less knowledge will have more nausea and disorientation compared to user that get used with game or vr application

Author Response

1. Abstract should free from citation , author should revise the abstract and remove any citation or reference. Author can move that citation to introduction section.

--> Corrected and revised as suggested.

2. I suggest author to add user testing picture during the four-condition testing (refer to Figure 3)

--> Figure 4 is added.

3. Author mention that more than 41 users recruited using online questionnaire? how author manage the different skills of user toward VR application? user with less knowledge will have more nausea and disorientation compared to user that get used with game or vr application

--> As indicated in the "Participants" section (which used to be "Subjects" section), we administered the MSSQ to filter out the too sensitive or insensitive subjects, as to test out our approach against the typical VR users.  As for the prior VR experience, while it could have had an effect on one's tolerance to VR sickness, our selection was solely based on the MSSQ results. Most subjects stated they had little to moderate degrees of prior VR usage. How exactly prior VR experience would influence the effect of our approach remains an interesting future topic.

Reviewer 2 Report

This paper presents the improvement of possible measures to reduce the extent of VR sickness by lowering the resolution of peripheral countervection visualization. The overall format of the article is acceptable. However, some serious issues regarding the abstract, results’ presentation/accuracy, and references need to be addressed, corrected, and revised. Please find the recommendation as follow.

1.    The abstract is not clear and confusing. There is no need to cite references in the abstract, and authors must use their own words to present the essence of the study. Also, never use abbreviations in the abstract. In line 8, “FOV” must replace with its complete name. I suggest rewriting the abstract, and since the authors use the MDPI template for their paper, remember to limit the abstract to 200 words.

2.    The “keywords” section is empty and must be filled with a few best keywords related to the study.

3.    The main weak point of this study is the limited number of references, which results in an inadequate presentation of the research background. The number of related works is 29, and some have been used many times. 

4.    In the mentioned related works, there is a big gap between the research objectives of this study and important topics concerning user presence, cognition, perception, and awareness, which all directly or indirectly impact VR sickness and shape user experience within virtual environments. The presence or specifically spatial presence of a user within a virtual environment is related to many variables such as the level of immersion (non-immersive, semi-immersive, and fully-immersive virtual environments), type of interaction with virtual objects, perception of the spatial factors of the virtual environment on a human scale, view usage patterns and the way that a user shifts between egocentric and exocentric viewpoints. The combination of user characteristics, features of virtual environments, characteristics of virtual objects like absence or presence of texture, types of spaces, and the way that users explore and navigate within the virtual environment to recognize the depth, estimate the distances, and perceive visual patterns impact user spatial presence and may lead in experiencing some levels of VR sickness. None of these topics have been discussed in this paper. As a guide, a few relevant published works are listed at the end of the review report, and the inclusion and citation of all of them are highly recommended.

5.    In section 3, line 124 is mentioned that (104o horizontal, vertical: 98o) is fixed to be used as a small FOV based on previous research. What is the reason for choosing this specific field of view and considering it a small FOV?

6.    In tables 1 and 2, there is no need to emphasize the significance level of values by using multiple star signs. Any value lower than 0.05 is significant and must be presented with a single star sign.

7.    The positions of Figures 6 and 7 are not correct and are not close to their definitions in the text. The positions of figures 8 and 9 are wrong and must be repositioned.

The list of recommended references can be found below:

Feng, Y.; Duives, D.C.; Hoogendoorn, S.P. Wayfinding Behaviour in a Multi-Level Building: A Comparative Study of HMD VR and Desktop VR. Adv. Eng. Informatics2022, 51, 101475, doi:10.1016/j.aei.2021.101475.

Azarby, S.; Rice, A. Spatial Perception Imperatives in Virtual Environments: Understanding the Impacts of View Usage Patterns on Spatial Design Decisions in Virtual Reality Systems. Buildings2023, 13, 160, doi:10.3390/buildings13010160.

Kelly, J.W.; Doty, T.A.; Ambourn, M.; Cherep, L.A. Distance Perception in the Oculus Quest and Oculus Quest 2. Front. Virtual Real.2022, 3, 1–7, doi:10.3389/frvir.2022.850471.

Rothe, S.; Kegeles, B.; Hußmann, H. Camera Heights in Cinematic Virtual Reality: How Viewers Perceive Mismatches between Camera and Eye Height. TVX 2019 - Proc. 2019 ACM Int. Conf. Interact. Exp. TV Online Video2019, 25–34, doi:10.1145/3317697.3323362.

Todd, C.; Mallya, S.; Majeed, S.; Rojas, J.; Naylor, K. VirtuNav: A Virtual Reality Indoor Navigation Simulator with Haptic and Audio Feedback for the Visually Impaired. IEEE SSCI 2014 - 2014 IEEE Symp. Ser. Comput. Intell. - CIR2AT 2014 2014 IEEE Symp. Comput. Intell. Robot. Rehabil. Assist. Technol. Proc.2014, 1–8, doi:10.1109/CIRAT.2014.7009734.

Vilar, E.; Rebelo, F.; Noriega, P. Indoor Human Wayfinding Performance Using Vertical and Horizontal Signage in Virtual Reality. Hum. Factors Ergon. Manuf.2014,24, 601–615, doi:10.1002/hfm.20503.

Jiang, C.F.; Li, Y.S. Development and Verification of a VR Platform to Evaluate Wayfinding Abilities. Proc. 31st Annu. Int. Conf. IEEE Eng. Med. Biol. Soc. Eng. Futur. Biomed. EMBC 20092009, 2396–2399, doi:10.1109/IEMBS.2009.5334919.

Allman, S.A.; Cordy, J.; Hall, J.P.; Kleanthous, V.; Lander, E.R. Exploring the Perception of Additional Information Content in 360° 3D VR Video for Teaching and Learning. Virtual Worlds2022,1, 1–17, doi:10.3390/virtualworlds1010001.

Azarby, S.; Rice, A. Understanding the Effects of Virtual Reality System Usage on Spatial Perception: The Potential Impacts of Immersive Virtual Reality on Spatial Design Decisions. Sustainability2022, 14, 10326, doi:10.3390/su141610326.

Suzer, O.K.; Olgunturk, N.; Guvenc, D. The Effects of Correlated Colour Temperature on Wayfinding: A Study in a Virtual Airport Environment. Displays2018, 51, 9–19, doi:10.1016/j.displa.2018.01.003.

Author Response

1.    The abstract is not clear and confusing. There is no need to cite references in the abstract, and authors must use their own words to present the essence of the study. Also, never use abbreviations in the abstract. 

In line 8, “FOV” must replace with its complete name. I suggest rewriting the abstract, and since the authors use the MDPI template for their paper, remember to limit the abstract to 200 words.

--> Corrected and revised as suggested.

2.    The “keywords” section is empty and must be filled with a few best keywords related to the study.

--> Keywords are filled.
 

3.    The main weak point of this study is the limited number of references, which results in an inadequate presentation of the research background. The number of related works is 29, and some have been used many times. 

-->  We added paragraphs and references discussing the concept of presence and immersion and how it relates to our study.  We did not incorporate all the references as suggested by the reviewer however.  We only highlighted the definition/concept of immersion/presence itself and how it might be affected by different factors.  As for, as the reverse optical flow introduces visual artifact and possibly lowered visual realism, we tried to explain such downside of our approach.

4.    In the mentioned related works, there is a big gap between the research objectives of this study and important topics concerning user presence, cognition, perception, and awareness, which all directly or indirectly impact VR sickness and shape user experience within virtual environments. The presence or specifically spatial presence of a user within a virtual environment is related to many variables such as the level of immersion (non-immersive, semi-immersive, and fully-immersive virtual environments), type of interaction with virtual objects, perception of the spatial factors of the virtual environment on a human scale, view usage patterns and the way that a user shifts between egocentric and exocentric viewpoints. The combination of user characteristics, features of virtual environments, characteristics of virtual objects like absence or presence of texture, types of spaces, and the way that users explore and navigate within the virtual environment to recognize the depth, estimate the distances, and perceive visual patterns impact user spatial presence and may lead in experiencing some levels of VR sickness. None of these topics have been discussed in this paper. As a guide, a few relevant published works are listed at the end of the review report, and the inclusion and citation of all of them are highly recommended.

--> See item 3.  Related work section was revised to reflect this review comment.
 
5.    In section 3, line 124 is mentioned that (104o horizontal, vertical: 98o) is fixed to be used as a small FOV based on previous research. What is the reason for choosing this specific field of view and considering it a small FOV?

--> The pertaining word was changed from "small" to "smaller".  The FOV of 104 horizontal, vertical: 98 was set so that we could compare our work to that of Xiao et al.  It is still "smaller" than the Pimax headset FOV.  

6.    In tables 1 and 2, there is no need to emphasize the significance level of values by using multiple star signs. Any value lower than 0.05 is significant and must be presented with a single star sign.

--> Corrected as advised.
 

7.    The positions of Figures 6 and 7 are not correct and are not close to their definitions in the text. The positions of figures 8 and 9 are wrong and must be re-positioned.

--> Figures were re-positioned as suggested.
 

Reviewer 3 Report

After carefully review the research article titled “Dynamically Adjusted and Peripheral Visualization of Reverse Optical Flow for VR Sickness Reduction”, I came to the conclusion that the researchers had done commendable job. The articles do not contain any of the aforementioned keywords, missing keywords. Over the past three years, a number of studies have been conducted in this field. It is recommended that to go with more recent papers from 2020-2023 and make the comparative analysis table/Chart with respect to your study piece to boost its accuracy motion sickness solution. Minor English Academic language improvement required.

Author Response

1. The articles do not contain any of the aforementioned keywords, missing keywords. 

--> Keywords have been added as pointed out.

2. Over the past three years, a number of studies have been conducted in this field. It is recommended that to go with more recent papers from 2020-2023 and make the comparative analysis table/Chart with respect to your study piece to boost its accuracy motion sickness solution. 

--> This was a very good suggesting but after thinking about it, we opted not to do this.  Our work only compares itself to two other notable work in VR sickness reduction: (1) peripheral overlay with stripe pattern as countervection flow and (2) dynamic FoV adjustment.  We cannot make direct comparison to any other work as for now.  Note that we do explain other possible approaches (although not compare) to VR sickness reduction in the Related work (e.g. rest frame theory).

3. Minor English Academic language improvement required.
--> We had a professional proofreading service revise our manuscript.