Visual hands

1-introduction/related-work/3-augmented-reality.tex

@@ -207,40 +207,45 @@ Mais, spécifique à la RA vs RV, le tangible et la main sont visibles, du moins
 \subsubsection{Manipulating with Virtual Hands}
 \label{ar_virtual_hands}
 
-Les techniques d'interactions dites \enquote{naturelles} sont celles qui permettent à l'utilisateur d'utiliser directement les mouvements de son corps comme interface d'entrée avec le système de \AR/\VR~\cite{billinghurst2015survey}.
+Natural UI allow the user to use their body movements directly as inputs with the \VE~\cite{billinghurst2015survey}.
-C'est la main qui nous permet de manipuler avec force et précision les objets réels de la vie de tous les jours (\secref{hand_anatomy}), et c'est donc les techniques d'interactions de mains virtuelles qui sont les plus naturelles pour manipuler des objets virtuels~\cite{laviola20173d}.
+Our hands allow us to manipulate real everyday objects with both strength and precision (\secref{grasp_types}), hence virtual hand interaction techniques seem the most natural way to manipulate virtual objects~\cite{laviola20173d}.
-Initialement suivi par des dispositifs de capture de mouvement sous forme de gants ou de contrôleurs, il est maintenant possible de suivre les mains d'un utilisateur en temps réel avec des caméra et algorithmes de vision par ordinateur intégrés nativement dans les casques de \AR~\cite{tong2023survey}.
+Initially tracked by active sensing devices such as gloves or controllers, it is now possible to track hands in real time using cameras and computer vision algorithms natively integrated into \AR/\VR headsets~\cite{tong2023survey}.
 
 La main de l'utilisateur est donc suivie et reconstruite dans le \VE sous forme d'une \emph{main virtuelle}~\cite{billinghurst2015survey,laviola20173d}.
 Les modèles les plus simples représentent la main sous forme d'un objet 3D rigide suivant les mouvements de la main réelle avec \qty{6}{\DoF} (position et orientation dans l'espace)~\cite{talvas2012novel}.
-Une alternative est de représenter seulement les bouts des doigts, as in \figref{lee2007handy}, voire de représenter la main sous forme d'un nuage de points, as in \figref{hilliges2012holodesk}.
+Une alternative est de représenter seulement les bouts des doigts, as in \figref{lee2007handy}, voire de représenter la main sous forme d'un nuage de points (\figref{hilliges2012holodesk_1}).
 Enfin, les techniques les plus courantes représentent l'ensemble du squelette de la main sous forme d'un modèle cinématique articulé (\secref{hand_anatomy}):
 Chaque phalange virtuelle est alors représentée avec certain \DoFs de rotations par rapport à la phalange précédente~\cite{borst2006spring}.
 
-Il existe plusieurs techniques pour simuler les contacts et l'interaction du modèle de main virtuelle avec les objets virtuels~\cite{laviola20173d}.
+The user's hand is therefore tracked and reconstructed as a \emph{virtual hand} model in the \VE ~\cite{billinghurst2015survey,laviola20173d}.
-Les techniques avec une approche heuristique utilisent des règles pour déterminer la sélection, la manipulation et le lâcher d'un objet, \eg in \figref{piumsomboon2014graspshell_1}.
+The simplest models represent the hand as a rigid 3D object that follows the movements of the real hand with \qty{6}{\DoF} (position and orientation in space)~\cite{talvas2012novel}.
-Mais les heuristiques produisent des comportements peu réalistes et sont limités aux cas prévus par les règles.
+An alternative is to model only the fingertips (\figref{lee2007handy}) or the whole hand (\figref{hilliges2012holodesk_1}) as points.
-À l'inverse, les techniques basées sur la physique simulent les forces aux points de contact de la main virtuelle avec l'objet.
+The most common technique is to reconstruct all the phalanges of the hand in an articulated kinematic model (\secref{hand_anatomy})~\cite{borst2006spring}.
-\textcite{borst2006spring} ont nottament proposé un modèle cinématique articulé dont chaque phalange est un rigid body simulé avec la méthode god-object~\cite{zilles1995constraintbased}: la phalange virtuelle les mouvements de la phalange réelle suivie mais reste contraintes à la surface des objets virtuels lors d'un contact. Les forces appliquées à l'objet sont calculées en fonction de la distance entre les mains réelles et virtuelles (\figref{borst2006spring}).
+
-Des techniques plus avancées simulent les phénomèmes de friction as in \secref{friction}~\cite{talvas2013godfinger} et les déformations des doigts~\cite{talvas2015aggregate}, permettant des interactions très réalistes.
+The contacts between the virtual hand model and the \VOs are then simulated using heuristic or physics-based techniques~\cite{laviola20173d}.
+Heuristic techniques use rules to determine the selection, manipulation and release of a \VO (\figref{piumsomboon2013userdefined_1}).
+But they produce unrealistic behaviour and are limited to the cases predicted by the rules.
+Physics-based techniques simulate forces at the contact points between the virtual hand and the \VO.
+In particular, \textcite{borst2006spring} have proposed an articulated kinematic model in which each phalanx is a rigid body simulated with the god-object~\cite{zilles1995constraintbased} method: the virtual phalanx follows the movements of the real phalanx, but remains constrained to the surface of the virtual objects during contact. The forces acting on the object are calculated as a function of the distance between the real and virtual hands (\figref{borst2006spring}).
+More advanced techniques simulate the friction phenomena described in \secref{friction}~\cite{talvas2013godfinger} and finger deformations~\cite{talvas2015aggregate}, allowing highly accurate and realistic interactions, but which can be difficult to compute in real time.
 
 \begin{subfigs}{virtual-hand}{Virtual hand interactions in \AR. }[
         \item A fingertip tracking that enables to select a \VO by opening the hand~\cite{lee2007handy}.
         \item Physics-based hand-object interactions with a virtual hand made of numerous many small rigid-body spheres~\cite{hilliges2012holodesk}.
-        \item Grasping through gestures when the fingers are detected as opposing on the object~\cite{piumsomboon2014graspshell}.
+        \item Grasping a through gestures when the fingers are detected as opposing on the \VO~\cite{piumsomboon2013userdefined}.
         \item A kinematic hand model with rigid-body phalanges (in beige) following the real tracked hand (in green) but kept physically constrained to the \VO. Applied force are displayed as red arrows~\cite{borst2006spring}.
     ]
-    \subfigsheight{35.5mm}
+    \subfigsheight{37mm}
     \subfig{lee2007handy}
-    \subfig{hilliges2012holodesk}
+    \subfig{hilliges2012holodesk_1}
-    \subfig{piumsomboon2014graspshell_1}
+    \subfig{piumsomboon2013userdefined_1}
     \subfig{borst2006spring}
 \end{subfigs}
 
-Cependant, le manque de contraintes physiques sur les mouvements de la main de l'utilisateur rend les actions de manipulation fatiguantes~\cite{hincapie-ramos2014consumed}.
+However, the lack of physical constraints on the user's hand movements makes manipulation actions tiring~\cite{hincapie-ramos2014consumed}.
-Les doigts de l'utilsateur vont également traverser l'objet virtuel tandis qu'une main virtuelle basée physique restera en contact avec l'objet, ce qui peut dégrader les performances de l'utilisateur en \VR~\cite{prachyabrued2012virtual}.
+While the fingers of the user traverse the virtual object, a physics-based virtual hand remains in contact with the object, a discrepancy that may degrade the user's performance in \VR~\cite{prachyabrued2012virtual}.
-Enfin, en l'absence de retour haptique sur chaque doigt, il est difficile d'estimer les contacts et les forces appliquées par les doigts sur l'objet pendant la saisie et la manipulation~\cite{maisto2017evaluation,meli2018combining}.
+Finally, in the absence of haptic feedback on each finger, it is difficult to estimate the contact and forces exerted by the fingers on the object during grasping and manipulation~\cite{maisto2017evaluation,meli2018combining}.
-Si le rendu visuel de la main virtuelle en \VR permet de compenser ces problèmes~\cite{prachyabrued2014visual}, la question de la représentation visuelle et haptique de la main virtuelle, ou leur combinaison, en \AR reste peu étudiée.
+While a visual rendering of the virtual hand in \VR can compensate for these issues~\cite{prachyabrued2014visual},, the visual and haptic rendering of the virtual hand, or their combination, in \AR is under-researched.
 
 
 \subsection{Visual Rendering of Hands in AR}
@@ -256,34 +261,44 @@ A visual hand rendering while in \VE also seems to affect how one grasps an obje
 \fig{prachyabrued2014visual}{Visual hand renderings affect user experience in \VR~\cite{prachyabrued2014visual}.}
 
 As presented in \secref{ar_displays}, a user sees their hands in \AR, and the mutual occlusion between the hands and the \VOs is a common issue, \ie hiding the \VO when the real hand is in front of it and hiding the real hand when it is behind the \VO.
-While in \VST-\AR, this could be solved as a masking problem by combining the real and virtual images~\cite{battisti2018seamless}, \eg in \figref{knorlein2009influence_1}, in \OST-\AR, this is much more difficult because the \VE is displayed as a transparent \TwoD image on top of the \ThreeD \RE, which cannot be easily masked~\cite{macedo2023occlusion}.
+For example, in \figref{hilliges2012holodesk_2}, the user is pinching a virtual cube in \OST-\AR with their thumb and index fingers, but while the index is behind the cube, it is seen as in front of it.
-For example, in \figref{hilliges2012holodesk}, the user is pinching a virtual cube in \OST-\AR with their thumb and index fingers, but while the index is behind the cube, it is seen as in front of it.
+While in \VST-\AR, this could be solved as a masking problem by combining the real and virtual images~\cite{battisti2018seamless}, \eg in \figref{suzuki2014grasping}, in \OST-\AR, this is much more difficult because the \VE is displayed as a transparent \TwoD image on top of the \ThreeD \RE, which cannot be easily masked~\cite{macedo2023occlusion}.
 %Yet, even in \VST-\AR,
 
-In \AR, as the hand of a user is visible but not physically constrained by the \VE, adding a visual rendering of the virtual hand that can physically interact with \VOs would achieve a similar result to the promising double-hand rendering of \textcite{prachyabrued2014visual}.
+As the \VE is intangible and the hand of the user visible while in \AR, adding a visual rendering of the virtual hand that is physically constrained to the \VOs would achieve a similar result to the promising double-hand rendering of \textcite{prachyabrued2014visual}.
-Additionally, \textcite{kahl2021investigation} showed that a \VO overlaying a tangible object in \OST-\AR can vary in size without worsening the users' experience nor the performance.
+Additionally, \textcite{kahl2021investigation} showed that a \VO overlaying a tangible object in \OST-\AR can vary in size without worsening the users' experience nor the performance when manipulating it.
 This suggests that a visual hand rendering superimposed on the real hand could be helpful, but should not impair users.
 
-An alternative is to render the \VOs and the virtual hand semi-transparents, so that they are partially visible even when one is occluding the other, \eg the real hand is behind the virtual cube but still visible as in \figref{piumsomboon2014graspshell}.
+An alternative is to render the \VOs and the virtual hand semi-transparents, so that they are partially visible even when one is occluding the other (\figref{buchmann2005interaction}).
 Although perceived as less natural, this seems to be preferred to a mutual visual occlusion in \VST-\AR~\cite{buchmann2005interaction,ha2014wearhand,piumsomboon2014graspshell} and \VR~\cite{vanveldhuizen2021effect}, but has not yet been evaluated in \OST-\AR.
 However, this effect still causes depth conflicts that make it difficult to determine if one's hand is behind or in front of a \VO, \eg the thumb is in front of the virtual cube, but could be perceived to be behind it.
 
 Few works have compared different visual hand rendering in \AR, nor with wearable haptic feedback.
-\textcite{blaga2017usability} evaluated direct hand manipulation in non-immersive \VST-\AR a skeleton-like rendering against no visual hand rendering: while user performance did not improve, participants felt more confident with the virtual hand.
+\textcite{blaga2017usability} evaluated direct hand manipulation in non-immersive \VST-\AR a skeleton-like rendering against no visual hand rendering: while user performance did not improve, participants felt more confident with the virtual hand (\figref{blaga2017usability}).
-\textcite{krichenbauer2018augmented} found participants \percent{22} faster in immersive \VST-\AR than in \VR in the same pick-and-place manipulation task.
+%\textcite{krichenbauer2018augmented} found participants \percent{22} faster in immersive \VST-\AR than in \VR in the same pick-and-place manipulation task.
-No visual hand rendering was used in \VR while the real hand was visible in \AR.
+%No visual hand rendering was used in \VR while the real hand was visible in \AR.
-In a collaboration task in immersive \OST-\AR \vs \VR with a remote partner, \textcite{yoon2020evaluating} found that a realistic human hand rendering was the most preferred over a low-polygon hand and a skeleton-like hand.
+In a collaboration task in immersive \OST-\AR \vs \VR, \textcite{yoon2020evaluating} showed that a realistic human hand rendering was the most preferred over a low-polygon hand and a skeleton-like hand for the remote partner.
-Finally, \textcite{maisto2017evaluation} and \textcite{meli2018combining} compared visual and haptic rendering of the virtual hand in \AR, as detailed in the next section (\secref{vhar_rings}).
+\textcite{genay2021virtual} found that the \SoE was stronger with robotic hands overlay in \OST-\AR when the environment contains \VOs (\figref{genay2021virtual}).
+Finally, \textcite{maisto2017evaluation} and \textcite{meli2018combining} compared visual and haptic rendering of the hand in \AR, as detailed in the next section (\secref{vhar_rings}).
+Taken together, these results suggest that a visual hand rendering in \AR could improve the user experience and performance in direct hand manipulation tasks, but the best rendering is still to be determined.
 %\cite{chan2010touching} : cues for touching (selection) \VOs.
 %\textcite{saito2021contact} found that masking the real hand with a textured 3D opaque virtual hand did not improve performance in a reach-to-grasp task but displaying the points of contact on the \VO did.
 %To the best of our knowledge, evaluating the role of a visual rendering of the hand displayed \enquote{and seen} directly above real tracked hands in immersive OST-AR has not been explored, particularly in the context of \VO manipulation.
 
-\begin{subfigs}{visual-hands}{Visual hand renderings of virtual hands in \AR. }
+\begin{subfigs}{visual-hands}{Visual hand renderings of virtual hands in \AR. }[
-    \subfigsheight{35mm}
+        \item Grasping a \VO in \OST-\AR with no visual hand rendering~\cite{hilliges2012holodesk}.
-    \subfig{piumsomboon2014graspshell_2}
+        \item Simulated mutual-occlusion between the hand grasping and the \VO in \VST-\AR~\cite{suzuki2014grasping}.
+        \item Grasping a real object with a semi-transparent hand in \VST-\AR~\cite{buchmann2005interaction}.
+        \item Skeleton rendering overlaying the real hand in \VST-\AR~\cite{blaga2017usability}.
+        \item Robotic rendering overlaying the real hands in \OST-\AR~\cite{genay2021virtual}.
+    ]
+    \subfigsheight{29mm}
+    \subfig{hilliges2012holodesk_2}
+    \subfig{suzuki2014grasping}
     \subfig{buchmann2005interaction}
     \subfig{blaga2017usability}
-    \subfig{yoon2020evaluating}
+    \subfig{genay2021virtual}
+    %\subfig{yoon2020evaluating}
 \end{subfigs}
 
 \subsection{Conclusion}

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