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Erwan Normand
2024-09-27 22:10:59 +02:00
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3-manipulation/visuo-haptic-hand/4-discussion.tex
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\section{Discussion}
\label{discussion}
We evaluated sixteen visuo-haptic renderings of the hand, in the same two virtual object manipulation tasks in \AR as in the \chapref{visual_hand}, as the combination of two vibrotactile contact techniques provided at four delocalized positions on the hand with the two most representative visual hand renderings established in the \chapref{visual_hand}.
We evaluated sixteen visuo-haptic renderings of the hand, in the same two \VO manipulation tasks in \AR as in the \chapref{visual_hand}, as the combination of two vibrotactile contact techniques provided at four delocalized positions on the hand with the two most representative visual hand renderings established in the \chapref{visual_hand}.
In the \level{Push} task, vibrotactile haptic hand rendering has been proven beneficial with the \level{Proximal} positioning, which registered a low completion time, but detrimental with the \level{Fingertips} positioning, which performed worse (\figref{results/Push-CompletionTime-Location-Overall-Means}) than the \level{Proximal} and \level{Opposite} (on the contralateral hand) positionings.
The cause might be the intensity of vibrations, which many participants found rather strong and possibly distracting when provided at the fingertips.
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Participants reported that this visual hand rendering provided good feedback on the status of the hand tracking while being constrained to the cube, and helped with rotation adjustment in both tasks.
However, many also felt that it was a bit redundant with the vibrotactile hand rendering.
Indeed, receiving a vibrotactile hand rendering was found by participants as a more accurate and reliable information regarding the contact with the cube than simply seeing the cube and the visual hand reacting to the manipulation.
This result suggests that providing a visual hand rendering may not be useful during the grasping phase, but may be beneficial prior to contact with the virtual object and during position and rotation adjustment, providing valuable information about the hand pose.
This result suggests that providing a visual hand rendering may not be useful during the grasping phase, but may be beneficial prior to contact with the \VO and during position and rotation adjustment, providing valuable information about the hand pose.
It is also worth noting that the improved hand tracking and grasp helper improved the manipulation of the cube with respect to the \chapref{visual_hand}, as shown by the shorter completion time during the \level{Grasp} task.
This improvement could also be the reason for the smaller differences between the \level{Skeleton} and the \level{None} visual hand renderings in this second experiment.
In summary, the positioning of the vibrotactile haptic rendering of the hand affected on the performance and experience of users manipulating virtual objects with their bare hands in \AR.
In summary, the positioning of the vibrotactile haptic rendering of the hand affected on the performance and experience of users manipulating \VOs with their bare hands in \AR.
The closer the vibrotactile hand rendering was to the point of contact, the better it was perceived in terms of effectiveness, usefulness, and realism.
These subjective appreciations of wearable haptic hand rendering for manipulating virtual objects in \AR were also observed by \textcite{maisto2017evaluation} and \textcite{meli2018combining}.
These subjective appreciations of wearable haptic hand rendering for manipulating \VOs in \AR were also observed by \textcite{maisto2017evaluation} and \textcite{meli2018combining}.
However, the best performance was obtained with the farthest positioning on the contralateral hand (\level{Opposite}), which is somewhat surprising.
This apparent paradox could be explained in two ways.
On the one hand, participants behave differently when the haptic rendering was given on the fingers (\level{Fingertips} and \level{Proximal}), close to the contact point, with shorter pushes and larger grip apertures.
This behavior has likely given them a better experience of the tasks and more confidence in their actions, as well as leading to a lower interpenetration/force applied to the cube \cite{pacchierotti2015cutaneous}.
On the other hand, the unfamiliarity of the contralateral hand positioning (\level{Opposite}) caused participants to spend more time understanding the haptic stimuli, which might have made them more focused on performing the task.
In terms of the contact vibration technique, the continuous vibration technique on the finger interpenetration (\level{Distance}) did not make a difference to performance, although it provided more information.
Participants felt that vibration bursts were sufficient (\level{Distance}) to confirm contact with the virtual object.
Participants felt that vibration bursts were sufficient (\level{Distance}) to confirm contact with the \VO.
Finally, it was interesting to note that the visual hand rendering was appreciated but felt less necessary when provided together with vibrotactile hand rendering, as the latter was deemed sufficient for acknowledging the contact.