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Erwan Normand
2024-10-10 15:51:50 +02:00
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4
2-perception/xr-perception/1-introduction.tex
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Still, it is known that the visual rendering of a tangible can influence the perception of its haptic properties (\secref[related_work]{visual_haptic_influence}), and that the perception of same haptic force-feedback or vibrotactile rendering can differ between \AR and \VR, probably due to difference in perceived simultaneity between visual and haptic stimuli (\secref[related_work]{ar_vr_haptic}).
Indeed, in \AR, the user can see their own hand touching, the haptic device worn and the \RE, while in \VR they are hidden by the \VE.
In this chapter, we investigate the \textbf{role of the visual virtuality} of the hand (real or virtual) and its environment (\AR or \VR) on the perception of a \textbf{tangible surface whose haptic roughness is augmented} with a wearable haptics.%voice-coil device worn on the finger.
To do so, we used the visuo-haptic system presented in \chapref{vhar_system} to render virtual vibrotactile patterned textures (\secref[related_work]{texture_rendering}) to augment the tangible surface being touched.% touched by the finger.% that can be directly touched with the bare finger.
In this chapter, we investigate the \textbf{role of the visual virtuality} of the hand (real or virtual) and its environment (\AR or \VR) on the perception of a \textbf{tangible surface whose haptic roughness is augmented} with a wearable haptics. %voice-coil device worn on the finger.
To do so, we used the visuo-haptic system presented in \chapref{vhar_system} to render virtual vibrotactile patterned textures (\secref[related_work]{texture_rendering}) to augment the tangible surface being touched. % touched by the finger.% that can be directly touched with the bare finger.
We evaluated, in \textbf{user study with psychophysical methods and extensive questionnaire}, the perceived roughness augmentation in three visual rendering conditions: \textbf{(1) without visual augmentation}, in \textbf{(2) \OST-\AR with a realistic virtual hand} rendering, and in \textbf{(3) \VR with the same virtual hand}.
To control for the influence of the visual rendering, the tangible surface was not visually augmented and stayed the same in all conditions.

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2-perception/xr-perception/4-results.tex
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]
\begin{subfigs}{discrimination_accuracy}{Results of the vibrotactile texture roughness discrimination task. }[][
\item Estimated \PSE of each visual rendering, defined as the amplitude difference at which both reference and comparison textures are perceived to be equivalent.%, \ie the accuracy in discriminating vibrotactile roughness.
\item Estimated \JND of each visual rendering.
%, defined as the minimum perceptual amplitude difference, \ie the sensitivity to vibrotactile roughness differences.
\item Estimated \PSE of each visual rendering, defined as the amplitude difference at which both reference and comparison textures are perceived to be equivalent. %, \ie the accuracy in discriminating vibrotactile roughness.
\item Estimated \JND of each visual rendering. %, defined as the minimum perceptual amplitude difference, \ie the sensitivity to vibrotactile roughness differences.
]
\subfig[0.35]{results/trial_pses}
\subfig[0.35]{results/trial_jnds}

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2-perception/xr-perception/5-discussion.tex
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@@ -8,7 +8,7 @@ A \PSE difference in the same range was found for perceived stiffness, with the
%However, the difference between the \level{Virtual} and \level{Mixed} conditions was not significant.
%
Surprisingly, the \PSE of the \level{Real} rendering was shifted to the right (to be "rougher", \percent{7.9}) compared to the reference texture, whereas the \PSEs of the \level{Virtual} (\percent{5.1}) and \level{Mixed} (\percent{1.9}) renderings were perceived as \enquote{smoother} and closer to the reference texture (\figref{results/trial_predictions}).
The sensitivity of participants to roughness differences also varied, with the \level{Real} rendering having the best \JND (\percent{26}), followed by the \level{Virtual} (\percent{30}) and \level{Virtual} (\percent{33}) renderings (\figref{results/trial_jnds}).
The sensitivity of participants to roughness differences also varied, with the \level{Real} rendering having the best \JND (\percent{26}), followed by the \level{Virtual} (\percent{30}) and \level{Mixed} (\percent{33}) renderings (\figref{results/trial_jnds}).
These \JND values are in line with and at the upper end of the range of previous studies \cite{choi2013vibrotactile}, which may be due to the location of the actuator on the top of the finger middle phalanx, being less sensitive to vibration than the fingertip.
Thus, compared to no visual rendering (\level{Real}), the addition of a visual rendering of the hand or environment reduced the roughness sensitivity (\JND) and the roughness perception (\PSE), as if the virtual vibrotactile textures felt \enquote{smoother}.