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Erwan Normand
2024-09-29 14:09:31 +02:00
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2
3-manipulation/visual-hand/2-method.tex
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@@ -146,7 +146,7 @@ Participants signed an informed consent, including the declaration of having no
Inspired by \textcite{laviolajr20173d}, we collected the following metrics during the experiment:
\begin{itemize}
\item \response{Completion Time}, defined as the time elapsed between the very first contact with the virtual cube and its correct placement inside the target volume; as subjects were asked to complete the tasks as fast as possible, lower completion times mean better performance.
\item \response{Completion Time}, defined as the time elapsed between the first contact with the virtual cube and its correct placement inside the target volume; as subjects were asked to complete the tasks as fast as possible, lower completion times mean better performance.
\item \response{Contacts}, defined as the number of separate times the user's hand makes contact with the virtual cube; in both tasks, a lower number of contacts means a smoother continuous interaction with the object.
\item \response{Time per Contact}, defined as the total time any part of the user's hand contacted the cube divided by the number of contacts; higher values mean that the user interacted with the object for longer non-interrupted periods of time.
\item \response{Grip Aperture} (solely for the grasp-and-place task), defined as the average distance between the thumb's fingertip and the other fingertips during the grasping of the cube; lower values indicate a greater finger interpenetration with the cube, resulting in a greater discrepancy between the real hand and the visual hand rendering constrained to the cube surfaces and showing how confident users are in their grasp \cite{prachyabrued2014visual, al-kalbani2016analysis, blaga2017usability, chessa2019grasping}.

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3-manipulation/visual-hand/4-discussion.tex
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@@ -10,7 +10,7 @@ Indeed, participants found the \level{None} and \level{Occlusion} renderings les
To understand whether the participants' previous experience might have played a role, we also carried out an additional statistical analysis considering \VR experience as an additional between-subjects factor, \ie \VR novices vs. \VR experts (\enquote{I use it every week}, see \secref{participants}).
We found no statistically significant differences when comparing the considered metrics between \VR novices and experts.
Interestingly, all visual hand renderings showed \response{Grip Apertures} very close to the size of the virtual cube, except for the \level{None} rendering (\figref{results/Grasp-GripAperture-Hand-Overall-Means}), with which participants applied stronger grasps, \ie less distance between the fingertips.
All visual hand renderings showed \response{Grip Apertures} close to the size of the virtual cube, except for the \level{None} rendering (\figref{results/Grasp-GripAperture-Hand-Overall-Means}), with which participants applied stronger grasps, \ie less distance between the fingertips.
Having no visual hand rendering, but only the reaction of the cube to the interaction as feedback, made participants less confident in their grip.
This result contrasts with the wrongly estimated grip apertures observed by \textcite{al-kalbani2016analysis} in an exocentric VST-AR setup.
Also, while some participants found the absence of visual hand rendering more natural, many of them commented on the importance of having feedback on the tracking of their hands, as observed by \textcite{xiao2018mrtouch} in a similar immersive OST-AR setup.

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3-manipulation/visuo-haptic-hand/2-method.tex
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@@ -83,14 +83,14 @@ This design led to a total of 5 vibrotactile positionings \x 2 vibration contact
\subsection{Apparatus and Procedure}
\label{apparatus}
Apparatus and experimental procedure were very similar to the \chapref{visual_hand}, as described in \secref[visual_hand]{apparatus} and \secref[visual_hand]{protocol}, respectively.
Apparatus and experimental procedure were similar to the \chapref{visual_hand}, as described in \secref[visual_hand]{apparatus} and \secref[visual_hand]{protocol}, respectively.
We report here only the differences.
We employed the same vibrotactile device used by \cite{devigne2020power}.
It is composed of two encapsulated \ERM (\secref[related_work]{vibrotactile_actuators}) vibration motors (Pico-Vibe 304-116, Precision Microdrive, UK).
They are small and very light (\qty{5}{\mm} \x \qty{20}{\mm}, \qty{1.2}{\g}) actuators capable of vibration frequencies from \qtyrange{120}{285}{\Hz} and
They are small and light (\qty{5}{\mm} \x \qty{20}{\mm}, \qty{1.2}{\g}) actuators capable of vibration frequencies from \qtyrange{120}{285}{\Hz} and
amplitudes from \qtyrange{0.2}{1.15}{\g}.
They have a latency of \qty{20}{\ms} that we partially compensated for at the software level with slightly larger colliders to trigger the vibrations very close the moment the finger touched the cube.
They have a latency of \qty{20}{\ms} that we partially compensated for at the software level with slightly larger colliders to trigger the vibrations close the moment the finger touched the cube.
These two outputs vary linearly together, based on the tension applied.
They were controlled by an Arduino Pro Mini (\qty{3.3}{\V}) and a custom board that delivered the tension independently to each motor.
A small \qty{400}{mAh} Li-ion battery allowed for 4 hours of constant vibration at maximum intensity.

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3-manipulation/visuo-haptic-hand/5-conclusion.tex
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@@ -9,8 +9,8 @@ In a user study, we compared sixteen visuo-haptic renderings of the hand as the
Results showed that delocalized vibrotactile haptic hand rendering improved the perceived effectiveness, realism, and usefulness when it is provided close to the contact point.
%However, the farthest positioning on the contralateral hand gave the best performance even though it was disliked: the unfamiliarity of the positioning probably caused the participants to take more effort to consider the haptic stimuli and to focus more on the task.
The visual hand rendering was perceived less necessary than the vibrotactile haptic hand rendering, but still provided a useful feedback on the hand tracking.
This study provide evidence that moving away the feedback from the inside of the hand is a simple but very promising approach for wearable haptics in \AR.
This study provide evidence that moving away the feedback from the inside of the hand is a simple but promising approach for wearable haptics in \AR.
If integration with the hand tracking system allows it, and if the task requires it, a haptic ring worn on the middle or proximal phalanx seems preferable.
However, a wrist-mounted haptic device will be able to provide richer feedback by embedding more diverse haptic actuators with larger bandwidths and maximum amplitudes, while being less obtrusive than a ring.
Finally, we think that the visual hand rendering complements the haptic hand rendering very well by providing continuous feedback on the hand tracking, and that it can be disabled during the grasping phase to avoid redundancy with the haptic feedback of the contact with the \VO.
Finally, we think that the visual hand rendering complements the haptic hand rendering well by providing continuous feedback on the hand tracking, and that it can be disabled during the grasping phase to avoid redundancy with the haptic feedback of the contact with the \VO.