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2-perception/xr-perception/1-introduction.tex
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@@ -19,7 +19,7 @@ To control for the influence of the visual rendering, the real surface was not v
\noindentskip In the remainder of this chapter, we first describe the experimental design and apparatus of the user study.
We then present the results obtained, discuss them, and outline recommendations for future \AR/\VR works using wearable haptic augmentations.
%First, we present a system for rendering virtual vibrotactile textures in real time without constraints on hand movements and integrated with an immersive visual \AR/\VR headset to provide a coherent multimodal visuo-haptic augmentation of the \RE.
%First, we present a system for rendering virtual vibrotactile textures in real time without constraints on hand movements and integrated with an immersive visual \AR/\VR headset to provide a coherent visuo-haptic augmentation of the \RE.
%An experimental setup is then presented to compare haptic roughness augmentation with an optical \AR headset (Microsoft HoloLens~2) that can be transformed into a \VR headset using a cardboard mask.
%We then conduct a psychophysical study with 20 participants, where various virtual haptic textures on a real surface directly touched with the finger are compared in a two-alternative forced choice (2AFC) task in three visual rendering conditions: (1) without visual augmentation, (2) with a realistic virtual hand rendering in \AR, and (3) with the same virtual hand in \VR.

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2-perception/xr-perception/3-experiment.tex
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@@ -114,51 +114,64 @@ They all signed an informed consent form before the user study and were unaware
For each trial, the \response{Texture Choice} by the participant as the roughest of the pair was recorded.
The \response{Response Time} between the end of the trial and the choice of the participant was also measured as an indicator of the difficulty of the task.
At each frame, the \response{Finger Position} and \response{Finger Speed} were recorded to control for possible differences in texture exploration behaviour.
Participants also rated their experience after each \factor{Visual Rendering} block of trials using the questions shown in \tabref{questions}.
After each \factor{Visual Rendering} block of trials, participants rated their experience with the vibrotactile textures (all blocks), the vibrotactile device (all blocks), the virtual hand rendering (all except \level{Mixed} block) and the \VE (\level{Virtual} block) using the questions shown in \tabref{questions}.
They also assessed their workload with the NASA Task Load Index (\response{NASA-TLX}) questionnaire after each blocks of trials.
After each \factor{Visual Rendering} block of trials, participants rated their experience with the vibrotactile textures (all blocks), the vibrotactile device (all blocks), the virtual hand rendering (all except \level{Mixed} block) and the \VE (\level{Virtual} block) using the questions shown in \tabref{questions1}.
They also assessed their workload with the NASA Task Load Index (\response{NASA-TLX}) questionnaire after each blocks of trials (\tabref{questions2}).
For all questions, participants were shown only labels (\eg \enquote{Not at all} or \enquote{Extremely}) and not the actual scale values (\eg 1 or 5) \cite{muller2014survey}.
\newcommand{\scalegroup}[2]{\multirow{#1}{1\linewidth}{#2}}
\begin{tabwide}{questions}
{Questions asked to participants after each \factor{Visual Rendering} block of trials.}
\afterpage{
\begin{tabwide}{questions1}
{First part of the questions asked to participants after each \factor{Visual Rendering} block of trials.}
[
Unipolar scale questions were 5-point Likert scales (1~=~Not at all, 2~=~Slightly, 3~=~Moderately, 4~=~Very and 5~=~Extremely).
Bipolar scale questions were 7-point Likert scales (1~=~Extremely A, 2~=~Moderately A, 3~=~Slightly A, 4~=~Neither A nor B, 5~=~Slightly B, 6~=~Moderately B, 7~=~Extremely B),
where A and B are the two poles of the scale (indicated in parentheses in the Scale column of the questions).
Participants were shown only the labels for all questions.
]
\begin{tabularx}{\linewidth}{l X p{0.2\linewidth}}
\toprule
\textbf{Code} & \textbf{Question} & \textbf{Scale} \\
\midrule
Texture Agency & Did the tactile sensations of texture seem to be caused by your movements? & \scalegroup{4}{Unipolar (1-5)} \\
Texture Realism & How realistic were the tactile textures? & \\
Texture Plausibility & Did you feel like you were actually touching textures? & \\
Texture Latency & Did the sensations of texture seem to lag behind your movements? & \\
\midrule
Vibration Location & Did the vibrations seem to come from the surface you were touching or did you feel them on the top of your finger? & Bipolar (1=surface, 7=finger) \\
Vibration Strength & Overall, how weak or strong were the vibrations? & Bipolar (1=weak, 7=strong) \\
Device Distraction & To what extent did the vibrotactile device distract you from the task? & \scalegroup{2}{Unipolar (1-5)} \\
Device Discomfort & How uncomfortable was it to use the vibrotactile device? & \\
\midrule
Hand Agency & Did the movements of the virtual hand seem to be caused by your movements? & \scalegroup{5}{Unipolar (1-5)} \\
Hand Similarity & How similar was the virtual hand to your own hand in appearance? & \\
Hand Ownership & Did you feel the virtual hand was your own hand? & \\
Hand Latency & Did the virtual hand seem to lag behind your movements? & \\
Hand Distraction & To what extent did the virtual hand distract you from the task? & \\
Hand Reference & Overall, did you focus on your own hand or the virtual hand to complete the task? & Bipolar (1=own, 7=virtual) \\
\midrule
Virtual Realism & How realistic was the virtual environment? & \scalegroup{2}{Unipolar (1-5)} \\
Virtual Similarity & How similar was the virtual environment to the real one? & \\
\bottomrule
\end{tabularx}
\end{tabwide}
}
\begin{tab}[!htb]{questions2}
{NASA-TLX questions asked to participants after each \factor{Visual Rendering} block of trials.}
[
Unipolar scale questions were 5-point Likert scales (1~=~Not at all, 2~=~Slightly, 3~=~Moderately, 4~=~Very and 5~=~Extremely).
Bipolar scale questions were 7-point Likert scales (1~=~Extremely A, 2~=~Moderately A, 3~=~Slightly A, 4~=~Neither A nor B, 5~=~Slightly B, 6~=~Moderately B, 7~=~Extremely B),
where A and B are the two poles of the scale (indicated in parentheses in the Scale column of the questions).
NASA TLX questions were bipolar 100-points scales (0~=~Very Low and 100~=~Very High, except for Performance where 0~=~Perfect and 100~=~Failure).
Questions were bipolar 100-points scales (0~=~Very Low and 100~=~Very High, except for Performance where 0~=~Perfect and 100~=~Failure).
Participants were shown only the labels for all questions.
]
\begin{tabularx}{\linewidth}{l X p{0.2\linewidth}}
\begin{tabularx}{\linewidth}{p{0.13\linewidth} X}
\toprule
\textbf{Code} & \textbf{Question} & \textbf{Scale} \\
\textbf{Code} & \textbf{Question} \\
\midrule
Texture Agency & Did the tactile sensations of texture seem to be caused by your movements? & \scalegroup{4}{Unipolar (1-5)} \\
Texture Realism & How realistic were the tactile textures? & \\
Texture Plausibility & Did you feel like you were actually touching textures? & \\
Texture Latency & Did the sensations of texture seem to lag behind your movements? & \\
\midrule
Vibration Location & Did the vibrations seem to come from the surface you were touching or did you feel them on the top of your finger? & Bipolar (1=surface, 7=finger) \\
Vibration Strength & Overall, how weak or strong were the vibrations? & Bipolar (1=weak, 7=strong) \\
Device Distraction & To what extent did the vibrotactile device distract you from the task? & \scalegroup{2}{Unipolar (1-5)} \\
Device Discomfort & How uncomfortable was it to use the vibrotactile device? & \\
\midrule
Hand Agency & Did the movements of the virtual hand seem to be caused by your movements? & \scalegroup{5}{Unipolar (1-5)} \\
Hand Similarity & How similar was the virtual hand to your own hand in appearance? & \\
Hand Ownership & Did you feel the virtual hand was your own hand? & \\
Hand Latency & Did the virtual hand seem to lag behind your movements? & \\
Hand Distraction & To what extent did the virtual hand distract you from the task? & \\
Hand Reference & Overall, did you focus on your own hand or the virtual hand to complete the task? & Bipolar (1=own, 7=virtual) \\
\midrule
Virtual Realism & How realistic was the virtual environment? & \scalegroup{2}{Unipolar (1-5)} \\
Virtual Similarity & How similar was the virtual environment to the real one? & \\
\midrule
Mental Demand & How mentally demanding was the task? & \scalegroup{6}{Bipolar (0-100)} \\
Temporal Demand & How hurried or rushed was the pace of the task? & \\
Physical Demand & How physically demanding was the task? & \\
Performance & How successful were you in accomplishing what you were asked to do? & \\
Effort & How hard did you have to work to accomplish your level of performance? & \\
Frustration & How insecure, discouraged, irritated, stressed, and annoyed were you? & \\
Mental Demand & How mentally demanding was the task? \\
Temporal Demand & How hurried or rushed was the pace of the task? \\
Physical Demand & How physically demanding was the task? \\
Performance & How successful were you in accomplishing what you were asked to do? \\
Effort & How hard did you have to work to accomplish your level of performance? \\
Frustration & How insecure, discouraged, irritated, stressed, and annoyed were you? \\
\bottomrule
\end{tabularx}
\end{tabwide}
\end{tab}

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2-perception/xr-perception/6-conclusion.tex
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@@ -1,13 +1,13 @@
\section{Conclusion}
\label{conclusion}
In this chapter, we studied how the perception of wearable haptic augmented textures is affected by the visual virtuality of the hand and the environment, being either real, augmented or virtual.
In this chapter, we studied how the perception of wearable haptic augmented textures is affected by the visual feedback of the virtual hand and the environment, being either real, augmented or virtual.
Using the wearable visuo-haptic augmentation system presented in \chapref{vhar_system}, we augmented the perceived roughness of real surfaces with virtual vibrotactile textures rendered on the finger.
%we rendered virtual vibrotactile patterned textures on the voice-coil worn on the middle-phalanx of the finger to augment the roughness perception of the real surface being touched.
With an immersive \AR headset, that could be switched to a \VR only view, we considered three visual rendering conditions: (1) without visual augmentation, (2) with a realistic virtual hand rendering in \AR, and (3) with the same virtual hand in \VR.
We then evaluated the perceived roughness augmentation in these three visual conditions with a psychophysical user study involving 20 participants and extensive questionnaires.
Our results showed that the visual virtuality of the hand and the environment had a significant effect on the perception of haptic textures and the exploration behaviour of the participants.
Our results showed that the visual virtuality of the hand (real or virtual) and the environment (\AR or \VR) had a significant effect on the perception of haptic textures and the exploration behaviour of the participants.
The textures were on average perceived as \enquote{rougher} and with a higher sensitivity when touched with the real hand alone than with a virtual hand either in \AR, with \VR in between.
Exploration behaviour was also slower in \VR than with real hand alone, although subjective evaluation of the texture was not affected.
We hypothesised that this difference in perception was due to the \emph{perceived latency} between the finger movements and the different visual, haptic and proprioceptive feedbacks, which were the same in all visual renderings, but were more noticeable in \AR and \VR than without visual augmentation.