Tangible VR Book: Exploring the Design Space of Marker-Based Tangible Interfaces for Virtual Reality

Round 1

Reviewer 1 Report

Dear Authors,

Your paper touches on a significant topic which is interaction in the VR environment. This is interesting for many reasons, mainly because VR development can be seen in many areas.

The article is presented solidly, however, after reading, some questions/thoughts arise:

1. What about objects connected with water? In the main physical characteristic which option could refer to imitate objects such as water? Would you consider an explanation of this characteristic based on literature?
2. I have a problem with a dimension of your design space called type of object. You’ve said that objects can be classified as reconfigurable and non-configurable. As an example of a reconfigurable object, you’ve picked an openable tower prototype. However, the only reconfigurable item is doors, and the building itself could be defined as immovable. Would you consider to define the type of not entire objects, but only parts of them?
3. It would be great if you would ask participants (who test VR book) about their experience with the VR environment as you did in a pilot study of prototypes. According to many experiences people which are more familiar with VR give often different looks than those who are slightly familiar. Probably this is not possible anymore.

Minor issues:

In line 178: you wrote that “user flips” and after you use “she”.

323: the acoustic properties of a physical object were only

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper examines the development of a design space, from user evaluation of different marker-based TUIs, culminating in development of a TUI book used in VR.

I have a significant research interest in VR so I was excited to review this paper!

The authors state that their primary contribution related to the "definition and exploration of a design space of marker-based TUI for VR", however whilst defined, I expected a more in depth review and discussion of that space. The authors have Figure 2, however I expected a similar figure in section 5 where it's first described. For the different dimensions, how to do they relate to one another? Are some mutually inclusive or exclusive? What does this design space allow us to do now that we have it? I feel that whilst the authors did some initial testing based on fiducial marker concepts, a further review of previous systems and literature would have also led to a richer design space. What parts of this relate just to VR vs possibly AR as well? Or all TUIs? For the primary contribution of the work, I was hoping to see a richer description and discussion of the space, as well as further discussion of the space relating to previous TUIs discussed in the background section and others.

Whilst the book is presented as a way of exploring the space, I also feel it was only loosely connected from different interaction techniques. Why is this a good example? Why have a slider in the book? If the book is used as THE defining example application of this design space, why is it a good one? I feel the paper explores a few different things (initial concept designs, design evaluation, design space conceptualisation, book design, and then evaluation of the book), however none of them are discussed in significant detail.

Regarding the background work, I'd suggest the reviewers look into Embodied Interaction as an overlap between input and output, e.g. an abacus. I'm not entirely sure of the citing of the Companion Novel as a related TUI. Whilst audio is mentioned, it's not heavily discussed in relation to TUIs specifically.

Regarding the discussion, where are the lessons learned? You report on their feedback, however what has been learned from that feedback? Obviously given the COVID-friendly evaluation limited your options, there needs to be retrospection for what these results mean on your input device, and more importantly, the design space.

I'd question the current value of the active vs passive TUI background section. I'd ask the authors go into more detail regarding prior work and the balance/trade off between active vs passive. Talking about opportunistic controls raises the idea of ad-hoc tangibles, see "Ephemeral interaction using everyday objects" (Walsh, et al.). The authors' focus on handheld VR, how does that impact the TUI design space? What TUIs work with one hand vs two, since the user is now holding the display? For non-immersive VR, the user can now also see the physical objects, as well as the VR view simultaneously, does this potentially impact the design space for good or bad? You mention other TUI design spaces briefly, however I think you could go into a little more detail (how were they developed, what has the resulting design space assisted with, etc.). Also, how does your resulting design space work with and compliment the prior ones? You're proposing another tool to the toolbox, how can it be used with existing tools?

Whilst I'm excited about the design space for TUIs, I can't at this point recommend the paper for publication. I encourage the authors to refine their goals and focus for the primary contribution, and write to that.

Other comments:

The authors comment that markers "need to be on flat surfaces" - what about marker tracking like Vuforia that handles cylinders and other objects?

- Figure 8 is incorrectly placed/labelled?

- Why have small videos?

- section 4.3: provide quick intro of the results. What is R1, R2, etc?

Would recommend an editing pass, checking the lines below as things I've found:

:246 explored?, what prototypes?, what

:331 if the tangible’s main role is input than it will be used to somehow affect the state of the VE

:338 In some situations it may not be easy to decide if the main role of a tangible is to act as a controller 339 (input) or as output of information >> embodied UIs

:339 Some tangibles

:349 image, graphics (e.g. computer generated graphics or animations) >> missing comma before audio. Missing "and" before video

:352 manually by the user, automatically by the system) >> OR

:421 Digital 3D Reconstruction of the Monastery of Santa Cruz in 1834 - reference

:506 confirm that ethics was first sought

:510 , and profession

:678 Covid-19 > COVID-19

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

The article proposes a smartphone based argument reality solution that supports tangible user interface. The topic is of general interesting. 

A few comments:

1. The mathematical formation of the problem can be elaborated, for example, how are the markers designed, what's the algorithm used for detecting the markers, how is the accuracy evaluated, etc.
2. The source code link is not accessible. It requires the organization's account which I believe neither the reviewers or general audience have it.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

I thank the authors for their response and edits based on my review.

I can understand the authors' desire to not have the design space as it relates to prior and existing TUIs, however I'd argue that one example doesn't justify a design space, as we can't be sure that additional dimensions aren't required, or that this design space hasn't been overly tailored the specific use case used. However, I do acknowledge the improvement in the contribution based on the edits.

How you justify to the authors that this design space is indeed universally applicable?

Author Response

Dear reviewer,

Thank you again for your comments and questions. Even though it is clear we did not completely meet the expectations, your comments have resulted in an improvement of the manuscript, in our opinion.

I can understand the authors' desire to not have the design space as it relates to prior and existing TUIs, however I'd argue that one example doesn't justify a design space, as we can't be sure that additional dimensions aren't required, or that this design space hasn't been overly tailored the specific use case used. However, I do acknowledge the improvement in the contribution based on the edits.

How you justify to the authors that this design space is indeed universally applicable?

This is, of course, a hard question and one we cannot prove. The main justification we can offer is the quality of the process of followed to arrive at the design space, involving prototype exploration, and formative studies. To us, more important than being universally applicable is that the design space is somehow useful in a design process. 

Kind regards,

The authors