WIP visuo-haptic hand

3-manipulation/visual-hand/2-method.tex

@@ -90,7 +90,7 @@ We analyzed the two tasks separately.
 For each of them, we considered two independent, within-subject, variables:
 \begin{itemize}
   \item \factor{Hand}, consisting of the six possible visual hand renderings discussed in \secref{hands}: \level{None}, \level{Occlusion} (Occl), \level{Tips}, \level{Contour} (Cont), \level{Skeleton} (Skel), and \level{Mesh}.
-  \item \factor{Target}, consisting of the eight possible location of the target volume, named as the cardinal points and as shown in \figref{tasks}: right (\level{R}), right-back (\level{RB}), back (\level{B}), left-back (\level{LB}), left (\level{L}), left-front (\level{LF}), front (\level{F}) and right-front (\level{RF}).
+  \item \factor{Target}, consisting of the eight possible locations of the target volume, named from the participant's point of view and as shown in \figref{tasks}: right (\level{R}), right-back (\level{RB}), back (\level{B}), left-back (\level{LB}), left (\level{L}), left-front (\level{LF}), front (\level{F}) and right-front (\level{RF}).
 
 \end{itemize}
 Each condition was repeated three times.

3-manipulation/visual-hand/3-1-push.tex

@@ -42,7 +42,7 @@ On the contrary, the lack of visual hand constrained the participants to give mo
 Targets on the left (\level{L}, \level{LF}) and the right (\level{R}) sides had higher \response{Timer per Contact} than all the other targets (\p{0.005}).
 
 \begin{subfigs}{push_results}{Results of the push task performance metrics for each visual hand rendering.}[
-    Geometric means with bootstrap 95~\% \CI
+    Geometric means with bootstrap \percent{95} \CI
     and Tukey's \HSD pairwise comparisons: *** is \pinf{0.001}, ** is \pinf{0.01}, and * is \pinf{0.05}.
   ][
   \item Time to complete a trial.

3-manipulation/visual-hand/3-2-grasp.tex

@@ -33,7 +33,7 @@ and \factor{Target} (\anova{7}{2868}{5.6}, \pinf{0.001}).
 It was shorter with \level{None} than with \level{Tips} (\qty{-15}{\%}, \pinf{0.001}), \level{Skeleton} (\qty{-11}{\%}, \p{0.001}) and \level{Mesh} (\qty{-11}{\%}, \p{0.001});
 shorter with \level{Occlusion} than with \level{Tips} (\qty{-10}{\%}, \pinf{0.001}), \level{Skeleton} (\qty{-8}{\%}, \p{0.05}), and \level{Mesh} (\qty{-8}{\%}, \p{0.04});
 shorter with \level{Contour} than with \level{Tips} (\qty{-8}{\%}, \pinf{0.001}).
-As for the \factor{Push} task, the lack of visual hand increased the number of failed grasps or cube drops.
+As for the \level{Push} task, the lack of visual hand increased the number of failed grasps or cube drops.
 The \level{Tips} rendering seemed to provide one of the best feedback for the grasping, maybe thanks to the fact that it provides information about both position and rotation of the tracked fingertips.
 
 This time was the shortest on the front \level{F} than on the other target volumes (\pinf{0.001}).
@@ -55,7 +55,7 @@ The \level{Mesh} rendering seemed to have provided the most confidence to partic
 The \response{Grip Aperture} was longer on the right-front (\level{RF}) target volume, indicating a higher confidence, than on back and side targets (\level{R}, \level{RB}, \level{B}, \level{L}, \p{0.03}).
 
 \begin{subfigs}{grasp_results}{Results of the grasp task performance metrics for each visual hand rendering.}[
-    Geometric means with bootstrap 95~\% \CI
+    Geometric means with bootstrap \percent{95} \CI
     and Tukey's \HSD pairwise comparisons: *** is \pinf{0.001}, ** is \pinf{0.01}, and * is \pinf{0.05}.
   ][
   \item Time to complete a trial.

3-manipulation/visual-hand/3-3-ranks.tex

@@ -1,7 +1,7 @@
 \subsection{Ranking}
 \label{ranks}
 
-\figref{results_ranks} shows the ranking of each visual \factor{Hand} rendering for the \factor{Push} and \factor{Grasp} tasks.
+\figref{results_ranks} shows the ranking of each visual \factor{Hand} rendering for the \level{Push} and \level{Grasp} tasks.
 Friedman tests indicated that both ranking had statistically significant differences (\pinf{0.001}).
 Pairwise Wilcoxon signed-rank tests with Holm-Bonferroni adjustment were then used on both ranking results (\secref{metrics}):
 

3-manipulation/visual-hand/4-discussion.tex

@@ -3,9 +3,9 @@
 
 We evaluated six visual hand renderings, as described in \secref{hands}, displayed on top of the real hand, in two virtual object manipulation tasks in \AR.
 
-During the \factor{Push} task, the \level{Skeleton} hand rendering was the fastest (\figref{results/Push-CompletionTime-Hand-Overall-Means}), as participants employed fewer and longer contacts to adjust the cube inside the target volume (\figref{results/Push-ContactsCount-Hand-Overall-Means} and \figref{results/Push-MeanContactTime-Hand-Overall-Means}).
+During the \level{Push} task, the \level{Skeleton} hand rendering was the fastest (\figref{results/Push-CompletionTime-Hand-Overall-Means}), as participants employed fewer and longer contacts to adjust the cube inside the target volume (\figref{results/Push-ContactsCount-Hand-Overall-Means} and \figref{results/Push-MeanContactTime-Hand-Overall-Means}).
 Participants consistently used few and continuous contacts for all visual hand renderings (Fig. 3b), with only less than ten trials, carried out by two participants, quickly completed with multiple discrete touches.
-However, during the \factor{Grasp} task, despite no difference in \response{Completion Time}, providing no visible hand rendering (\level{None} and \level{Occlusion} renderings) led to more failed grasps or cube drops (\figref{results/Grasp-CompletionTime-Hand-Overall-Means} and \figref{results/Grasp-MeanContactTime-Hand-Overall-Means}).
+However, during the \level{Grasp} task, despite no difference in \response{Completion Time}, providing no visible hand rendering (\level{None} and \level{Occlusion} renderings) led to more failed grasps or cube drops (\figref{results/Grasp-CompletionTime-Hand-Overall-Means} and \figref{results/Grasp-MeanContactTime-Hand-Overall-Means}).
 Indeed, participants found the \level{None} and \level{Occlusion} renderings less effective (\figref{results/Ranks-Grasp}) and less precise (\figref{results_questions}).
 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.

3-manipulation/visuo-haptic-hand/2-method.tex

@@ -36,7 +36,7 @@ We considered two representative contact vibration techniques, \ie two ways of r
 
 The implementation of these two techniques have been tuned according to the results of a preliminary experiment.
 Three participants were asked to carry out a series of push and grasp tasks similar to those used in the actual experiment.
-Results showed that 95~\% of the contacts between the fingertip and the virtual cube happened at speeds below \qty{1.5}{\m\per\s}.
+Results showed that \percent{95} of the contacts between the fingertip and the virtual cube happened at speeds below \qty{1.5}{\m\per\s}.
 We also measured the perceived minimum amplitude to be 15~\% (\qty{0.6}{\g}) of the maximum amplitude of the motors we used.
 For this reason, we designed the Impact vibration technique (Impa) so that contact speeds from \qtyrange{0}{1.5}{\m\per\s} are linearly mapped into \qtyrange{15}{100}{\%} amplitude commands for the motors.
 Similarly, we designed the distance vibration technique (Dist) so that interpenetrations from \qtyrange{0}{2.5}{\cm} are linearly mapped into \qtyrange{15}{100}{\%} amplitude commands for the motors, recalling that the virtual cube has an edge of \qty{5}{\cm}.
@@ -44,50 +44,39 @@ Similarly, we designed the distance vibration technique (Dist) so that interpene
 \section{User Study}
 \label{method}
 
-This user study aims to evaluate whether a visuo-haptic hand rendering affects the user performance and experience of manipulation of \VOs with bare hands in \OST-\AR.
-The chosen visuo-haptic hand renderings are the combination of the two most representative visual hand renderings established in the first experiment, \ie \level{Skeleton} and \level{None}, described in \secref[visual_hand]{hands}, with the two contact vibration techniques provided at the four delocalized positions on the hand described in \secref{vibration}.
+This user study aims to evaluate whether a visuo-haptic rendering of the hand affects the user performance and experience of manipulation of \VOs with bare hands in \OST-\AR.
+The chosen visuo-haptic hand renderings are the combination of the two most representative visual hand renderings established in the \chapref{visual_hand}, \ie \level{Skeleton} and \level{None}, described in \secref[visual_hand]{hands}, with the two contact vibration techniques provided at the four delocalized positions on the hand described in \secref{vibration}.
 
 \subsection{Experimental Design}
 \label{design}
 
+We considered the same two \level{Push} and \level{Grasp} tasks as described in \secref[visual_hand]{tasks}, that we analyzed separately, considering four independent, within-subject variables:
+
+\begin{itemize}
+  \item \factor{Positioning}: the five positionings for providing vibrotactile hand rendering of the virtual contacts, as described in \secref{positioning}.
+  \item \factor{Vibration Technique}: the two contact vibration techniques, as described in \secref{technique}.
+  \item \factor{Hand}: two visual hand renderings from the first experiment, \level{Skeleton} (Skel) and \level{None}, as described in \secref[visual_hand]{hands}; we considered \level{Skeleton} as it performed the best in terms of performance and perceived effectiveness and \level{None} as reference.
+  \item \factor{Target}: we considered the target volumes (\figref{tasks}), from the participant's point of view, located at:
+    \begin{itemize}
+      \item left-bottom (\level{LB}) and left-right (\level{LF}) during the \level{Push} task; and
+      \item right-bottom (\level{RB}), left-bottom (\level{LB}), left-right (\level{LF}) and right-front (\level{RF}) during the \level{Grasp} task.
+    \end{itemize}. We considered these targets because they presented different difficulties.
+\end{itemize}
+
 \begin{subfigs}{tasks}{The two manipulation tasks of the user study.}[
     Both pictures show the cube to manipulate in the middle (\qty{5}{\cm} and opaque) and the eight possible targets to reach (\qty{7}{\cm} cube and semi-transparent).
     Only one target at a time was shown during the experiments.
   ][
-  \item Pushing a virtual cube along a table toward a target placed on the same surface.
-  \item Grasping and lifting a virtual cube toward a target placed on a \qty{20}{\cm} higher plane.
+  \item Push task: pushing the virtual cube along a table towards a target placed on the same surface.
+  \item Grasp task: grasping and lifting the virtual cube towards a target placed on a \qty{20}{\cm} higher plane.
   ]
-  \subfig[0.23]{method/task-push}
-  \subfig[0.23]{method/task-grasp}
+  \subfig[0.45]{method/task-push}
+  \subfig[0.45]{method/task-grasp}
 \end{subfigs}
 
-\begin{subfigs}{push_results}{Results of the grasp task performance metrics.}[
-    Geometric means with bootstrap 95~\% \CI for each vibrotactile positioning (a, b and c) or visual hand rendering (d)
-    and Tukey's \HSD pairwise comparisons: *** is \pinf{0.001}, ** is \pinf{0.01}, and * is \pinf{0.05}.
-  ][
-  \item Time to complete a trial.
-  \item Number of contacts with the cube.
-  \item Mean time spent on each contact.
-  \item Mean time spent on each contact.
-  ]
-  \subfig[0.24]{results/Push-CompletionTime-Location-Overall-Means}
-  \subfig[0.24]{results/Push-Contacts-Location-Overall-Means}
-  \subfig[0.24]{results/Push-TimePerContact-Location-Overall-Means}
-  \subfig[0.24]{results/Push-TimePerContact-Hand-Overall-Means}
-\end{subfigs}
-
-We considered the same two tasks as described in \secref[visual_hand]{tasks}, that we analyzed separately, considering four independent, within-subject variables:
-
-\begin{itemize}
-  \item \emph{{Vibrotactile Positioning}:} the five positionings for providing vibrotactile hand rendering of the virtual contacts, as described in \secref{positioning}.
-  \item \emph{Contact Vibration Technique}: the two contact vibration techniques, as described in \secref{technique}.
-  \item \emph{visual Hand rendering}: two visual hand renderings from the first experiment, \level{Skeleton} (Skel) and \level{None}, as described in \secref[visual_hand]{hands}; we considered \level{Skeleton} as it performed the best in terms of performance and perceived effectiveness and \level{None} as reference.
-  \item \emph{Target}: we considered target volumes located at \level{LB} and \level{LF} during the \factor{Push} task, and at \level{RB}, \level{LB}, \level{LF}, and \level{RF} during the \factor{Grasp} task (\figref{tasks}); we considered these targets because they presented different difficulties.
-\end{itemize}
-
-To account for learning and fatigue effects, the positioning of the vibrotactile hand rendering (positioning) was counter-balanced using a balanced \numproduct{10 x 10} Latin square.
-In these ten blocks, all possible Technique \x Hand \x Target combination conditions were repeated three times in a random order.
-As we did not find any relevant effect of the order in which the tasks were performed in the first experiment, we fixed the order of the tasks: first, the \factor{Push} task and then the \factor{Grasp} task.
+To account for learning and fatigue effects, the order of the \factor{Positioning} conditions were counter-balanced using a balanced \numproduct{10 x 10} Latin square.
+In these ten blocks, all possible \factor{Technique} \x \factor{Hand} \x \factor{Target} combination conditions were repeated three times in a random order.
+As we did not find any relevant effect of the order in which the tasks were performed in the first experiment, we fixed the order of the tasks: first, the \level{Push} task and then the \level{Grasp} task.
 
 This design led to a total of 5 vibrotactile positionings \x 2 vibration contact techniques \x 2 visual hand rendering \x (2 targets on the Push task + 4 targets on the Grasp task) \x 3 repetitions $=$ 420 trials per participant.
 
@@ -95,84 +84,58 @@ This design led to a total of 5 vibrotactile positionings \x 2 vibration contact
 \label{apparatus}
 
 Apparatus and protocol were very similar to the first experiment, 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 Eccentric Rotating Mass (ERM) 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
 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.
-%
 These two outputs vary linearly together, based on the tension applied.
-%
-They were controlled by an Arduino Pro Mini (3.3 V) and a custom board that delivered the tension independently to each motor.
-%
+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.
-%
 A Bluetooth module (RN42XV module, Microchip Technology Inc., USA) mounted on the Arduino ensured wireless communication with the HoloLens~2.
 
 To ensure minimal encumbrance, we used the same two motors throughout the experiment, moving them to the considered positioning before each new block.
-%
 Thin self-gripping straps were placed on the five positionings, with an elastic strap stitched on top to place the motor, as shown in \figref{method/locations}.
-%
 The straps were fixed during the entirety of the experiment to ensure similar hand tracking conditions.
-%
 We confirmed that this setup ensured a good transmission of the rendering and guaranteed a good hand tracking performance, that was measured to be constant (\qty{15}{\ms}) with and without motors, regardless their positioning.
-%
 The control board was fastened to the arm with an elastic strap.
-%
 Finally, participants wore headphones diffusing brown noise to mask the sound of the vibrotactile motors.
 
 We improved the hand tracking performance of the system by placing on the table a black sheet that absorbs the infrared light as well as placing the participants in front of a wall to ensure a more constant exposure to the light.
-%
 We also made grasping easier by adding a grasping helper, similar to UltraLeap's Physics Hands.\footnoteurl{https://docs.ultraleap.com/unity-api/Preview/physics-hands.html}.
-%
 When a phalanx collider of the tracked hand contacts the virtual cube,
-%
 a spring with a low stiffness is created and attached between the cube and the collider.
-%
 The spring pulls gently the cube toward the phalanxes in contact with the object to help maintain a natural and stable grasp.
-%
 When the contact is lost, the spring is destroyed.
-%
 Preliminary tests confirmed this approach.
 
+\subsection{Participants}
+\label{participants}
+
+Twenty subjects participated in the study (mean age = 26.8, \sd{4.1}; 19~males, 1~female).
+One was left-handed, while the other nineteen were right-handed. They all used their dominant hand during the trials.
+They all had a normal or corrected-to-normal vision.
+Thirteen subjects participated also in the previous experiment.
+
+Participants rated their expertise (\enquote{I use it more than once a year}) with \VR, \AR, and haptics in a pre-experiment questionnaire.
+There were twelve experienced with \VR, eight experienced with \AR, and ten experienced with haptics.
+VR and haptics expertise were highly correlated (\pearson{0.9}), as well as \AR and haptics expertise (\pearson{0.6}).
+Other expertise correlations were low ($r<0.35$).
+
 \subsection{Collected Data}
 \label{metrics}
 
 During the experiment, we collected the same data as in the first experiment, see \secref[visual_hand]{metrics}.
-%
 At the end of the experiment, participants were asked if they recognized the different contact vibration techniques.
-%
-They then rated the ten combinations of Positioning \x Technique using a 7-item Likert scale (1=Not at all, 7=Extremely):
-%
-\emph{(Vibration Rating)} How much do you like each vibrotactile rendering? %
-\emph{(Workload)} How demanding or frustrating was each vibrotactile rendering? %
-\emph{(Usefulness)} How useful was each vibrotactile rendering? %
-\emph{(Realism)} How realistic was each vibrotactile rendering?
-%
-Finally, they rated the ten combinations of Positioning \x Hand on a 7-item Likert scale (1=Not at all, 7=Extremely): %
-\emph{(positioning \x Hand Rating)} How much do you like each combination of vibrotactile location for each visual hand rendering?
+They then rated the ten combinations of \factor{Positioning} \x \factor{Vibration Technique} using a 7-item Likert scale (1=Not at all, 7=Extremely):
+\begin{itemize}
+  \item \response{Vibration Rating}: How much do you like each vibrotactile rendering?
+  \item \response{Workload}: How demanding or frustrating was each vibrotactile rendering?
+  \item \response{Usefulness}: How useful was each vibrotactile rendering?
+  \item \response{Realism}: How realistic was each vibrotactile rendering?
+\end{itemize}
 
-\subsection{Participants}
-\label{participants}
-
-Twenty subjects participated in the study (mean age = 26.8, SD = 4.1; 19~males, 1~female).
-%
-One was left-handed, while the other nineteen were right-handed. They all used their dominant hand during the trials.
-%
-They all had a normal or corrected-to-normal vision.
-%
-Thirteen subjects participated also in the previous experiment.
-
-Participants rated their expertise (\enquote{I use it more than once a year}) with \VR, \AR, and haptics in a pre-experiment questionnaire.
-%
-There were twelve experienced with \VR, eight experienced with \AR, and ten experienced with haptics.
-%
-VR and haptics expertise were highly correlated (\pearson{0.9}), as well as \AR and haptics expertise (\pearson{0.6}).
-%
-Other expertise correlations were low ($r<0.35$).
+Finally, they rated the ten combinations of \factor{Positioning} \x factor{Hand} on a 7-item Likert scale (1=Not at all, 7=Extremely):
+\response{Positioning \x Hand Rating}: How much do you like each combination of vibrotactile location for each visual hand rendering?

3-manipulation/visuo-haptic-hand/3-0-results.tex

@@ -2,12 +2,12 @@
 \label{results}
 
 \begin{subfigs}{grasp_results}{Results of the grasp task performance metrics for each vibrotactile positioning.}[
-    Geometric means with bootstrap 95~\% confidence and Tukey's \HSD pairwise comparisons: *** is \pinf{0.001}, ** is \pinf{0.01}, and * is \pinf{0.05}.
+    Geometric means with bootstrap \percent{95} confidence and Tukey's \HSD pairwise comparisons: *** is \pinf{0.001}, ** is \pinf{0.01}, and * is \pinf{0.05}.
   ][
   \item Time to complete a trial.
   \item Number of contacts with the cube.
   \item Time spent on each contact.
-  \item \level{Distance} between thumb and the other fingertips when grasping.
+  \item Distance between thumb and the other fingertips when grasping.
   ]
   \subfig[0.24]{results/Grasp-CompletionTime-Location-Overall-Means}
   \subfig[0.24]{results/Grasp-Contacts-Location-Overall-Means}
@@ -16,6 +16,5 @@
 \end{subfigs}
 
 Results were analyzed similarly as for the first experiment (\secref{results}).
-%
-The \LMM were fitted with the order of the five vibrotactile positionings (Order), the vibrotactile positionings (Positioning), the visual hand rendering (Hand), the {contact vibration techniques} (Technique), and the target volume position (Target), and their interactions as fixed effects and Participant as random intercept.
+The \LMM were fitted with the order of the five vibrotactile positionings (\factor{Order}), the vibrotactile positionings (\factor{Positioning}), the visual hand rendering (\factor{Hand}), the {contact vibration techniques} (\factor{Vibration Technique}), and the target volume position (\factor{Target}), and their interactions as fixed effects and Participant as random intercept.
 

3-manipulation/visuo-haptic-hand/3-1-push.tex

@@ -4,42 +4,46 @@
 \subsubsection{Completion Time}
 \label{push_tct}
 
-On the time to complete a trial, there were two statistically significant effects: %
-Positioning (\anova{4}{1990}{3.8}, \p{0.004}, see \figref{results/Push-CompletionTime-Location-Overall-Means}) %
-and Target (\anova{1}{1990}{3.9}, \p{0.05}).
-%
-\level{Fingertips} was slower than \level{Proximal} (\qty{+11}{\%}, \p{0.01}) or \level{Opposite} (\qty{+12}{\%}, \p{0.03}).
-%
+On the time to complete a trial, there were two statistically significant effects:
+\factor{Positioning} (\anova{4}{1990}{3.8}, \p{0.004}, see \figref{results/Push-CompletionTime-Location-Overall-Means}) %
+and \factor{Target} (\anova{1}{1990}{3.9}, \p{0.05}).
+\level{Fingertips} was slower than \level{Proximal} (\percent{+11}, \p{0.01}) or \level{Opposite} (\percent{+12}, \p{0.03}).
 There was no evidence of an advantage of \level{Proximal} or \level{Opposite} on \level{Nowhere}, nor a disadvantage of \level{Fingertips} on \level{Nowhere}.
-%
 Yet, there was a tendency of faster trials with \level{Proximal} and \level{Opposite}.
-%
 The \level{LB} target volume was also faster than the \level{LF} (\p{0.05}).
 
 \subsubsection{Contacts}
 \label{push_contacts_count}
 
-On the number of contacts, there was one statistically significant effect of %
-Positioning (\anova{4}{1990}{2.4}, \p{0.05}, see \figref{results/Push-Contacts-Location-Overall-Means}).
-%
-More contacts were made with \level{Fingertips} than with \level{Opposite} (\qty{+12}{\%}, \p{0.03}).
-%
+On the number of contacts, there was one statistically significant effect of
+\factor{Positioning} (\anova{4}{1990}{2.4}, \p{0.05}, see \figref{results/Push-Contacts-Location-Overall-Means}).
+More contacts were made with \level{Fingertips} than with \level{Opposite} (\percent{+12}, \p{0.03}).
 This could indicate more difficulties to adjust the virtual cube inside the target volume.
 
 \subsubsection{Time per Contact}
 \label{push_time_per_contact}
 
-On the mean time spent on each contact, there were two statistically significant effects of %
-Positioning (\anova{4}{1990}{11.5}, \pinf{0.001}, see \figref{results/Push-TimePerContact-Location-Overall-Means}) %
-and of Hand (\anova{1}{1990}{16.1}, \pinf{0.001}, see \figref{results/Push-TimePerContact-Hand-Overall-Means})%
-but not of the Positioning \x Hand interaction.
-%
-It was shorter with \level{Fingertips} than with \level{Wrist} (\qty{-15}{\%}, \pinf{0.001}), \level{Opposite} (\qty{-11}{\%}, \p{0.01}), or NoVi (\qty{-15}{\%}, \pinf{0.001});
-%
-and shorter with \level{Proximal} than with \level{Wrist} (\qty{-16}{\%}, \pinf{0.001}), \level{Opposite} (\qty{-12}{\%}, \p{0.005}), or \level{Nowhere} (\qty{-16}{\%}, \pinf{0.001}).
-%
+On the mean time spent on each contact, there were two statistically significant effects of
+\factor{Positioning} (\anova{4}{1990}{11.5}, \pinf{0.001}, see \figref{results/Push-TimePerContact-Location-Overall-Means}) %
+and of \factor{Hand} (\anova{1}{1990}{16.1}, \pinf{0.001}, see \figref{results/Push-TimePerContact-Hand-Overall-Means})%
+but not of the \factor{Positioning} \x \factor{Hand} interaction.
+It was shorter with \level{Fingertips} than with \level{Wrist} (\percent{-15}, \pinf{0.001}), \level{Opposite} (\percent{-11}, \p{0.01}), or NoVi (\percent{-15}, \pinf{0.001});
+and shorter with \level{Proximal} than with \level{Wrist} (\percent{-16}, \pinf{0.001}), \level{Opposite} (\percent{-12}, \p{0.005}), or \level{Nowhere} (\percent{-16}, \pinf{0.001}).
 This showed different strategies to adjust the cube inside the target volume, with faster repeated pushes with the \level{Fingertips} and \level{Proximal} positionings.
-%
-It was also shorter with \level{None} than with \level{Skeleton} (\qty{-9}{\%}, \pinf{0.001}).
-%
+It was also shorter with \level{None} than with \level{Skeleton} (\percent{-9}, \pinf{0.001}).
 This indicates, as for the first experiment, more confidence with a visual hand rendering.
+
+\begin{subfigs}{push_results}{Results of the grasp task performance metrics.}[
+    Geometric means with bootstrap \percent{95} \CI for each vibrotactile positioning (a, b and c) or visual hand rendering (d)
+    and Tukey's \HSD pairwise comparisons: *** is \pinf{0.001}, ** is \pinf{0.01}, and * is \pinf{0.05}.
+  ][
+  \item Time to complete a trial.
+  \item Number of contacts with the cube.
+  \item Mean time spent on each contact.
+  \item Mean time spent on each contact.
+  ]
+  \subfig[0.24]{results/Push-CompletionTime-Location-Overall-Means}
+  \subfig[0.24]{results/Push-Contacts-Location-Overall-Means}
+  \subfig[0.24]{results/Push-TimePerContact-Location-Overall-Means}
+  \subfig[0.24]{results/Push-TimePerContact-Hand-Overall-Means}
+\end{subfigs}

3-manipulation/visuo-haptic-hand/3-2-grasp.tex

@@ -4,56 +4,42 @@
 \subsubsection{Completion Time}
 \label{grasp_tct}
 
-On the time to complete a trial, there were two statistically significant effects: %
-Positioning (\anova{4}{3990}{13.6}, \pinf{0.001}, see \figref{results/Grasp-CompletionTime-Location-Overall-Means}) %
-and Target (\anova{3}{3990}{18.8}, \pinf{0.001}).
-%
-\level{\level{Opposite}} was faster than \level{Fingertips} (\qty{+19}{\%}, \pinf{0.001}), \level{Proximal} (\qty{+13}{\%}, \pinf{0.001}), \level{Wrist} (\qty{+14}{\%}, \pinf{0.001}), and \level{Nowhere} (\qty{+8}{\%}, \p{0.03}).
-%
-\level{Nowhere} was faster than \level{Fingertips} (\qty{+11}{\%}, \pinf{0.001}).
-%
+On the time to complete a trial, there were two statistically significant effects:
+\factor{Positioning} (\anova{4}{3990}{13.6}, \pinf{0.001}, see \figref{results/Grasp-CompletionTime-Location-Overall-Means})
+and \factor{Target} (\anova{3}{3990}{18.8}, \pinf{0.001}).
+\level{\level{Opposite}} was faster than \level{Fingertips} (\percent{+19}, \pinf{0.001}), \level{Proximal} (\percent{+13}, \pinf{0.001}), \level{Wrist} (\percent{+14}, \pinf{0.001}), and \level{Nowhere} (\percent{+8}, \p{0.03}).
+\level{Nowhere} was faster than \level{Fingertips} (\percent{+11}, \pinf{0.001}).
 \level{RF} was faster than \level{RB} (\pinf{0.001}), \level{LB} (\pinf{0.001}), and \level{LF} (\pinf{0.001});
-%
 and \level{LF} was faster than \level{RB} (\p{0.03}).
 
 \subsubsection{Contacts}
 \label{grasp_contacts_count}
 
-On the number of contacts, there were two statistically significant effects: %
-Positioning (\anova{4}{3990}{15.1}, \pinf{0.001}, see \figref{results/Grasp-Contacts-Location-Overall-Means}) %
-and Target (\anova{3}{3990}{7.6}, \pinf{0.001}).
-%
-Fewer contacts were made with \level{Opposite} than with \level{Fingertips} (\qty{-26}{\%}, \pinf{0.001}), \level{Proximal} (\qty{-17}{\%}, \pinf{0.001}), or \level{Wrist} (\qty{-12}{\%}, \p{0.002});
-%
-but more with \level{Fingertips} than with \level{Wrist} (\qty{+13}{\%}, \p{0.002}) or \level{Nowhere} (\qty{+17}{\%}, \pinf{0.001}).
-%
+On the number of contacts, there were two statistically significant effects:
+\factor{Positioning} (\anova{4}{3990}{15.1}, \pinf{0.001}, see \figref{results/Grasp-Contacts-Location-Overall-Means}) %
+and \factor{Target} (\anova{3}{3990}{7.6}, \pinf{0.001}).
+Fewer contacts were made with \level{Opposite} than with \level{Fingertips} (\percent{-26}, \pinf{0.001}), \level{Proximal} (\percent{-17}, \pinf{0.001}), or \level{Wrist} (\percent{-12}, \p{0.002});
+but more with \level{Fingertips} than with \level{Wrist} (\percent{+13}, \p{0.002}) or \level{Nowhere} (\percent{+17}, \pinf{0.001}).
 It was also easier on \level{LF} than on \level{RB} (\pinf{0.001}), \level{LB} (\p{0.006}), or \level{RF} (\p{0.03}).
 
 \subsubsection{Time per Contact}
 \label{grasp_time_per_contact}
 
-On the mean time spent on each contact, there were two statistically significant effects: %
-Positioning (\anova{4}{3990}{2.9}, \p{0.02}, see \figref{results/Grasp-TimePerContact-Location-Overall-Means}) %
-and Target (\anova{3}{3990}{62.6}, \pinf{0.001}).
-%
-It was shorter with \level{Fingertips} than with \level{Opposite} (\qty{+7}{\%}, \p{0.01}).
-%
+On the mean time spent on each contact, there were two statistically significant effects:
+\factor{Positioning} (\anova{4}{3990}{2.9}, \p{0.02}, see \figref{results/Grasp-TimePerContact-Location-Overall-Means})
+and \factor{Target} (\anova{3}{3990}{62.6}, \pinf{0.001}).
+It was shorter with \level{Fingertips} than with \level{Opposite} (\percent{+7}, \p{0.01}).
 It was also shorter on \level{RF} than on \level{RB}, \level{LB} or \level{LF} (\pinf{0.001});
-%
 but longer on \level{LF} than on \level{RB} or \level{LB} (\pinf{0.001}).
 
 \subsubsection{Grip Aperture}
 \label{grasp_grip_aperture}
 
 On the average distance between the thumb's fingertip and the other fingertips during grasping, there were two
-statistically significant effects: %
-Positioning (\anova{4}{3990}{30.1}, \pinf{0.001}, see \figref{results/Grasp-GripAperture-Location-Overall-Means}) %
-and Target (\anova{3}{3990}{19.9}, \pinf{0.001}).
-%
+statistically significant effects:
+\factor{Positioning} (\anova{4}{3990}{30.1}, \pinf{0.001}, see \figref{results/Grasp-GripAperture-Location-Overall-Means})
+and \factor{Target} (\anova{3}{3990}{19.9}, \pinf{0.001}).
 It was longer with \level{Fingertips} than with \level{Proximal} (\pinf{0.001}), \level{Wrist} (\pinf{0.001}), \level{Opposite} (\pinf{0.001}), or \level{Nowhere} (\pinf{0.001});
-%
 and longer with \level{Proximal} than with \level{Wrist} (\pinf{0.001}) or \level{Nowhere} (\pinf{0.001}).
-%
 But, it was shorter with \level{RB} than with \level{LB} or \level{LF} (\pinf{0.001});
-%
 and shorter with \level{RF} than with \level{LB} or \level{LF} (\pinf{0.001}).

3-manipulation/visuo-haptic-hand/3-3-questions.tex

@@ -2,22 +2,63 @@
 \label{technique_results}
 
 Seven participants were able to correctly discriminate between the two vibration techniques, which they described as the contact vibration (being the \level{Impact} technique) and the continuous vibration (being the \level{Distance} technique) respectively.
-%
 Seven participants said they only felt differences of intensity with a weak one (being the \level{Impact} technique) and a strong one (being the \level{Distance} technique).
-%
 Six participants did not notice the difference between the two vibration techniques.
-%
-There was no evidence that the ability to discriminate the vibration techniques was correlated with the participants' haptic or AR/VR expertise (\pearson{0.4}), nor that it had a statistically significant effect on the performance in the tasks.
-%
+There was no evidence that the ability to discriminate the vibration techniques was correlated with the participants' haptic or \AR/\VR expertise (\pearson{0.4}), nor that it had a statistically significant effect on the performance in the tasks.
 As the tasks had to be completed as quickly as possible, we hypothesize that little attention was devoted to the different vibration techniques.
-%
 Indeed, some participants explained that the contact cues were sufficient to indicate whether the cube was being properly pushed or grasped.
-%
 Although the \level{Distance} technique provided additional feedback on the interpenetration of the finger with the cube, it was not strictly necessary to manipulate the cube quickly.
 
 \subsection{Questionnaire}
 \label{questions}
 
+\figref{results_questions} shows the questionnaire results for each vibrotactile positioning.
+Questionnaire results were analyzed using \ART non-parametric \ANOVA (\secref{metrics}).
+Statistically significant effects were further analyzed with post-hoc pairwise comparisons with Holm-Bonferroni adjustment.
+Wilcoxon signed-rank tests were used for main effects and \ART contrasts procedure for interaction effects.
+Only significant results are reported.
+
+\subsubsection{Vibrotactile Rendering Rating}
+\label{vibration_ratings}
+
+There was a main effect of \factor{Positioning} (\anova{4}{171}{27.0}, \pinf{0.001}).
+Participants preferred \level{Fingertips} more than \level{Wrist} (\p{0.01}), \level{Opposite} (\pinf{0.001}), and \level{Nowhere} (\pinf{0.001});
+\level{Proximal} more than \level{Wrist} (\p{0.007}), \level{Opposite} (\pinf{0.001}), and \level{Nowhere} (\pinf{0.001});
+And \level{Wrist} more than \level{Opposite} (\p{0.01}) and \level{Nowhere} (\pinf{0.001}).
+
+\subsubsection{Positioning \x Hand Rating}
+\label{positioning_hand}
+
+There were two main effects of \factor{Positioning} (\anova{4}{171}{20.6}, \pinf{0.001}) and of \factor{Hand} (\anova{1}{171}{12.2}, \pinf{0.001}).
+Participants preferred \level{Fingertips} more than \level{Wrist} (\p{0.03}), \level{Opposite} (\pinf{0.001}), and \level{Nowhere} (\pinf{0.001});
+\level{Proximal} more than \level{Wrist} (\p{0.003}), \level{Opposite} (\pinf{0.001}), and \level{Nowhere} (\pinf{0.001});
+\level{Wrist} more than \level{Opposite} (\p{0.03}) and \level{Nowhere} (\pinf{0.001});
+And \level{Skeleton} more than No \factor{Hand} (\pinf{0.001}).
+
+\subsubsection{Workload}
+\label{workload}
+
+There was a main effect of \factor{Positioning} (\anova{4}{171}{3.9}, \p{0.004}).
+Participants found \level{Opposite} more fatiguing than \level{Fingertips} (\p{0.01}), \level{Proximal} (\p{0.003}), and \level{Wrist} (\p{0.02}).
+
+\subsubsection{Usefulness}
+\label{usefulness}
+
+There was a main effect of \factor{Positioning} (\anova{4}{171}{38.0}, \p{0.041}).
+Participants found \level{Fingertips} the most useful, more than \level{Proximal} (\p{0.02}), \level{Wrist} (\pinf{0.001}), \level{Opposite} (\pinf{0.001}), and \level{Nowhere} (\pinf{0.001});
+\level{Proximal} more than \level{Wrist} (\p{0.008}), \level{Opposite} (\pinf{0.001}), and \level{Nowhere} (\pinf{0.001});
+\level{Wrist} more than \level{Opposite} (\p{0.008}) and \level{Nowhere} (\pinf{0.001});
+And \level{Opposite} more than \level{Nowhere} (\p{0.004}).
+
+\subsubsection{Realism}
+\label{realism}
+
+There was a main effect of \factor{Positioning} (\anova{4}{171}{28.8}, \pinf{0.001}).
+Participants found \level{Fingertips} the most realistic, more than \level{Proximal} (\p{0.05}), \level{Wrist} (\p{0.004}), \level{Opposite} (\pinf{0.001}), and \level{Nowhere} (\pinf{0.001});
+\level{Proximal} more than \level{Wrist} (\p{0.03}), \level{Opposite} (\pinf{0.001}), and \level{Nowhere} (\pinf{0.001});
+\level{Wrist} more than \level{Opposite} (\p{0.03}) and \level{Nowhere} (\pinf{0.001});
+And \level{Opposite} more than \level{Nowhere} (\p{0.03}).
+
 \begin{subfigs}{results_questions}{Boxplots of the questionnaire results for each vibrotactile positioning.}[
     Pairwise Wilcoxon signed-rank tests with Holm-Bonferroni adjustment: *** is \pinf{0.001}, ** is \pinf{0.01}, and * is \pinf{0.05}.
     Higher is better for \textbf{(a)} vibrotactile rendering rating, \textbf{(c)} usefulness and \textbf{(c)} fatigue.
@@ -28,70 +69,3 @@ Although the \level{Distance} technique provided additional feedback on the inte
   \subfig[0.24]{results/Question-Realism-Positioning-Overall}
   \subfig[0.24]{results/Question-Workload-Positioning-Overall}
 \end{subfigs}
-
-\figref{results_questions} shows the questionnaire results for each vibrotactile positioning.
-%
-Questionnaire results were analyzed using \ART non-parametric \ANOVA (\secref{metrics}).
-%
-Statistically significant effects were further analyzed with post-hoc pairwise comparisons with Holm-Bonferroni adjustment.
-%
-Wilcoxon signed-rank tests were used for main effects and \ART contrasts procedure for interaction effects.
-%
-Only significant results are reported.
-
-\subsubsection{Vibrotactile Rendering Rating}
-\label{vibration_ratings}
-
-There was a main effect of Positioning (\anova{4}{171}{27.0}, \pinf{0.001}).
-%
-Participants preferred \level{Fingertips} more than \level{Wrist} (\p{0.01}), \level{Opposite} (\pinf{0.001}), and No Vibration (\pinf{0.001});
-%
-\level{Proximal} more than \level{Wrist} (\p{0.007}), \level{Opposite} (\pinf{0.001}), and No Vibration (\pinf{0.001});
-%
-And \level{Wrist} more than \level{Opposite} (\p{0.01}) and No Vibration (\pinf{0.001}).
-
-\subsubsection{Positioning \x Hand Rating}
-\label{positioning_hand}
-
-There were two main effects of Positioning (\anova{4}{171}{20.6}, \pinf{0.001}) and of Hand (\anova{1}{171}{12.2}, \pinf{0.001}).
-%
-Participants preferred \level{Fingertips} more than \level{Wrist} (\p{0.03}), \level{Opposite} (\pinf{0.001}), and No Vibration (\pinf{0.001});
-%
-\level{Proximal} more than \level{Wrist} (\p{0.003}), \level{Opposite} (\pinf{0.001}), and No Vibration (\pinf{0.001});
-%
-\level{Wrist} more than \level{Opposite} (\p{0.03}) and No Vibration (\pinf{0.001});
-%
-And \level{Skeleton} more than No Hand (\pinf{0.001}).
-
-\subsubsection{Workload}
-\label{workload}
-
-There was a main effect of Positioning (\anova{4}{171}{3.9}, \p{0.004}).
-%
-Participants found \level{Opposite} more fatiguing than \level{Fingertips} (\p{0.01}), \level{Proximal} (\p{0.003}), and \level{Wrist} (\p{0.02}).
-
-\subsubsection{Usefulness}
-\label{usefulness}
-
-There was a main effect of Positioning (\anova{4}{171}{38.0}, \p{0.041}).
-%
-Participants found \level{Fingertips} the most useful, more than \level{Proximal} (\p{0.02}), \level{Wrist} (\pinf{0.001}), \level{Opposite} (\pinf{0.001}), and \level{Nowhere} (\pinf{0.001});
-%
-\level{Proximal} more than \level{Wrist} (\p{0.008}), \level{Opposite} (\pinf{0.001}), and \level{Nowhere} (\pinf{0.001});
-%
-\level{Wrist} more than \level{Opposite} (\p{0.008}) and \level{Nowhere} (\pinf{0.001});
-%
-And \level{Opposite} more than \level{Nowhere} (\p{0.004}).
-
-\subsubsection{Realism}
-\label{realism}
-
-There was a main effect of Positioning (\anova{4}{171}{28.8}, \pinf{0.001}).
-%
-Participants found \level{Fingertips} the most realistic, more than \level{Proximal} (\p{0.05}), \level{Wrist} (\p{0.004}), \level{Opposite} (\pinf{0.001}), and \level{Nowhere} (\pinf{0.001});
-%
-\level{Proximal} more than \level{Wrist} (\p{0.03}), \level{Opposite} (\pinf{0.001}), and \level{Nowhere} (\pinf{0.001});
-%
-\level{Wrist} more than \level{Opposite} (\p{0.03}) and \level{Nowhere} (\pinf{0.001});
-%
-And \level{Opposite} more than \level{Nowhere} (\p{0.03}).

3-manipulation/visuo-haptic-hand/4-discussion.tex

@@ -3,94 +3,48 @@
 
 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 \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.
-%
+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.
-%
 This result was also observed by \textcite{bermejo2021exploring}, who provided vibrotactile cues when pressing a virtual keypad.
-%
 Another reason could be the visual impairment caused by the vibrotactile motors when worn on the fingertips, which could have disturbed the visualization of the virtual cube.
 
 We observed different strategies than in the first experiment for the two tasks.
-%
-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}).
-%
-During the \factor{Grasp}  task, participants pressed the cube 25~\% harder on average (\figref{results/Grasp-GripAperture-Location-Overall-Means}).
-%
+During the \level{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 \level{Grasp}  task, participants pressed the cube 25~ harder on average (\figref{results/Grasp-GripAperture-Location-Overall-Means}).
 The \level{Fingertips} and \level{Proximal} positionings led to a slightly larger grip aperture than the others.
-%
 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.
-%
 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.
-%
 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 \level{Opposite} positioning also seemed to be faster (\figref{results/Push-CompletionTime-Location-Overall-Means}) than having no vibrotactile hand rendering (\level{Nowhere} positioning).
-%
-However, participants also felt more workload (\figref{questions}) with this positioning opposite to the site of the interaction.
-%
+However, participants also felt more workload (\figref{results_questions}) with this positioning opposite to the site of the interaction.
 This result might mean that participants focused more on learning to interpret these sensations, which led to better performance in the long run.
 
 Overall, many participants appreciated the vibrotactile hand renderings, commenting that they made the tasks more realistic and easier.
-%
-However, the closer to the contact point, the better the vibrotactile rendering was perceived (\figref{questions}).
-%
+However, the closer to the contact point, the better the vibrotactile rendering was perceived (\figref{results_questions}).
 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.
-%
 While the majority of participants discriminated the two different techniques, only a minority identified them correctly (\secref{technique_results}).
-%
 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 \factor{Push} task, where the \level{Skeleton} hand rendering resulted again in longer contacts.
-%
+No difference in performance was found between the two visual hand renderings, except for the \level{Push} task, where the \level{Skeleton} hand rendering resulted again in longer contacts.
 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.
-%
 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.
-%
-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.
-%
+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 \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.
-%
 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}.
-%
-However, the best performance was obtained with the farthest positioning on the contralateral hand, which is somewhat surprising.
-%
+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, close to the contact point, with shorter pushes and larger grip apertures.
-%
+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 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} technique) did not make a difference to performance, although it provided more information.
-%
-Participants felt that vibration bursts were sufficient (Impact technique) to confirm contact with the virtual object.
-%
+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.
 Finally, it was interesting to note that the visual hand renderings was appreciated but felt less necessary when provided together with vibrotactile hand rendering, as the latter was deemed sufficient for acknowledging the contact.
-
-As we already said in \secref[visual_hand]{discussion}, these results have some limitations as they address limited types of visuo-haptic renderings and manipulations were restricted to the thumb and index fingertips.
-%
-While the simpler vibration technique (Impact technique) was sufficient to confirm contacts with the cube, richer vibrotactile renderings may be required for more complex interactions, such as collision or friction renderings between objects \cite{kuchenbecker2006improving, pacchierotti2015cutaneous} or texture rendering \cite{culbertson2014one, asano2015vibrotactile}.
-%
-More generally, a broader range of haptic sensations should be considered, such as pressure or stretching of the skin \cite{maisto2017evaluation, teng2021touch}.
-%
-However, moving the point of application of the sensation away may be challenging for some types of haptic rendering.
-%
-Similarly, as the interactions were limited to the thumb and index fingertips, positioning a delocalized haptic rendering over a larger area of the hand could be challenging and remains to be explored.
-%
-Also, given that some users found the vibration rendering too strong, adapting/personalizing the haptic feedback to one's preference (and body positioning) might also be a promising approach.
-%
-Indeed, personalized haptics is recently gaining interest in the community \cite{malvezzi2021design, umair2021exploring}.

3-manipulation/visuo-haptic-hand/visuo-haptic-hand.tex

@@ -5,7 +5,7 @@
 
 \input{1-introduction}
 \input{2-method}
-\input{3-results}
+\input{3-0-results}
 \input{3-1-push}
 \input{3-2-grasp}
 \input{3-3-questions}