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Fix vh-hand chapter

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Erwan Normand
2024-09-25 09:00:03 +02:00
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3-manipulation/visuo-haptic-hand/4-discussion.tex
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We evaluated sixteen visuo-haptic renderings of the hand, in the same two virtual object manipulation tasks in \AR as in the first experiment, 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 first experiment.
In the Push task, vibrotactile haptic hand rendering has been proven beneficial with the Proximal positioning, which registered a low completion time, but detrimental with the Fingertips positioning, which performed worse (\figref{results/Push-CompletionTime-Location-Overall-Means}) than the Proximal and Opposite (on the contralateral hand) positionings.
In the \factor{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.
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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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@@ -13,19 +13,19 @@ Another reason could be the visual impairment caused by the vibrotactile motors
We observed different strategies than in the first experiment for the two tasks.
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During the Push task, participants made more and shorter contacts to adjust the cube inside the target volume (\figref{results/Push-Contacts-Location-Overall-Means} and \figref{results/Push-TimePerContact-Location-Overall-Means}).
During the \factor{Push} task, participants made more and shorter contacts to adjust the cube inside the target volume (\figref{results/Push-Contacts-Location-Overall-Means} and \figref{results/Push-TimePerContact-Location-Overall-Means}).
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During the Grasp task, participants pressed the cube 25~\% harder on average (\figref{results/Grasp-GripAperture-Location-Overall-Means}).
During the \factor{Grasp} task, participants pressed the cube 25~\% harder on average (\figref{results/Grasp-GripAperture-Location-Overall-Means}).
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The Fingertips and Proximal positionings led to a slightly larger grip aperture than the others.
The \level{Fingertips} and \level{Proximal} positionings led to a slightly larger grip aperture than the others.
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We think that the proximity of the vibrotactile rendering to the point of contact made users to take more time to adjust their grip in a more realistic manner, \ie closer to the surface of the cube.
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This could also be the cause of the higher number of failed grasps or cube drops: indeed, we observed that the larger the grip aperture, the higher the number of contacts.
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Consequently, the Fingertips positioning was slower (\figref{results/Grasp-CompletionTime-Location-Overall-Means}) and more prone to error (\figref{results/Grasp-Contacts-Location-Overall-Means}) than the Opposite and Nowhere positionings.
Consequently, the \level{Fingertips} positioning was slower (\figref{results/Grasp-CompletionTime-Location-Overall-Means}) and more prone to error (\figref{results/Grasp-Contacts-Location-Overall-Means}) than the \level{Opposite} and \level{Nowhere} positionings.
In both tasks, the Opposite positioning also seemed to be faster (\figref{results/Push-CompletionTime-Location-Overall-Means}) than having no vibrotactile hand rendering (Nowhere positioning).
In both tasks, the \level{Opposite} positioning also seemed to be faster (\figref{results/Push-CompletionTime-Location-Overall-Means}) than having no vibrotactile hand rendering (\level{Nowhere} positioning).
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However, participants also felt more workload (\figref{questions}) with this positioning opposite to the site of the interaction.
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@@ -35,17 +35,17 @@ Overall, many participants appreciated the vibrotactile hand renderings, comment
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However, the closer to the contact point, the better the vibrotactile rendering was perceived (\figref{questions}).
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This seemed inversely correlated with the performance, except for the Nowhere positioning, \eg both the Fingertips and Proximal positionings were perceived as more effective, useful, and realistic than the other positionings despite lower performance.
This seemed inversely correlated with the performance, except for the \level{Nowhere} positioning, \eg both the \level{Fingertips} and \level{Proximal} positionings were perceived as more effective, useful, and realistic than the other positionings despite lower performance.
Considering the two tasks, no clear difference in performance or appreciation was found between the two contact vibration techniques.
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While the majority of participants discriminated the two different techniques, only a minority identified them correctly (\secref{technique_results}).
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It seemed that the Impact technique was sufficient to provide contact information compared to the Distance technique, which provided additional feedback on interpenetration, as reported by participants.
It seemed that the Impact technique was sufficient to provide contact information compared to the \level{Distance} technique, which provided additional feedback on interpenetration, as reported by participants.
No difference in performance was found between the two visual hand renderings, except for the Push task, where the Skeleton hand rendering resulted again in longer contacts.
No difference in performance was found between the two visual hand renderings, except for the \factor{Push} task, where the \level{Skeleton} hand rendering resulted again in longer contacts.
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Additionally, the Skeleton rendering was appreciated and perceived as more effective than having no visual hand rendering, confirming the results of our first experiment.
Additionally, the \level{Skeleton} rendering was appreciated and perceived as more effective than having no visual hand rendering, confirming the results of our first experiment.
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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.
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@@ -55,9 +55,9 @@ Indeed, receiving a vibrotactile hand rendering was found by participants as a m
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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.
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It is also worth noting that the improved hand tracking and grasp helper improved the manipulation of the cube with respect to the first experiment, as shown by the shorter completion time during the Grasp task.
It is also worth noting that the improved hand tracking and grasp helper improved the manipulation of the cube with respect to the first experiment, as shown by the shorter completion time during the \factor{Grasp} task.
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This improvement could also be the reason for the smaller differences between the Skeleton and the None visual hand renderings in this second experiment.
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.
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@@ -75,7 +75,7 @@ This behavior has likely given them a better experience of the tasks and more co
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On the other hand, the unfamiliarity of the contralateral hand positioning caused participants to spend more time understanding the haptic stimuli, which might have made them more focused on performing the task.
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In terms of the contact vibration technique, the continuous vibration technique on the finger interpenetration (Distance technique) did not make a difference to performance, although it provided more information.
In terms of the contact vibration technique, the continuous vibration technique on the finger interpenetration (\level{Distance} technique) did not make a difference to performance, although it provided more information.
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Participants felt that vibration bursts were sufficient (Impact technique) to confirm contact with the virtual object.
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