Perspectives

4-conclusion/conclusion.tex

@@ -62,7 +62,8 @@ In our system, we registered the real and virtual environments (\secref[related_
 This only allowed us to track the index finger and the surface to be augmented with the haptic texture, but the tracking was reliable and accurate enough for our needs.
 In fact, preliminary tests we conducted showed that the built-in tracking capabilities of the Microsoft HoloLens~2 were not able to track the hands wearing a voice-coil.
 A more robust hand tracking system would support wearing haptic devices on the hand, as well as holding real objects.
-A complementary solution would be to embed tracking sensors in the wearable haptic devices, such as an inertial measurement unit (IMU) or cameras, such as \textcite{preechayasomboon2021haplets}.
+A complementary solution would be to embed tracking sensors in the wearable haptic devices, such as an inertial measurement unit (IMU) or cameras \cite{preechayasomboon2021haplets}.
+Prediction of hand movements should also considered as well \cite{klein2020predicting,gamage2021predictable}
 This would allow a complete portable and wearable visuo-haptic system to be used in more ecological applications.
 
 \subsection*{Perception of Haptic Texture Augmentation in Augmented and Virtual Reality}
@@ -78,7 +79,7 @@ In particular, it remains to be investigated how the vibrotactile patterned text
 Our study was conducted with an \OST-\AR headset, but the results may be different with a \VST-\AR headset, where the \RE is seen through cameras and screens (\secref[related_work]{ar_displays}), and the perceived simultaneity between visual and haptic stimuli, real or virtual, is different.
 The effect of perceived visuo-haptic simultaneity on the augmented haptic perception and its size should also be systematically investigated, for example by inducing various delays between the visual and haptic feedback.
 We also focused on the perception of roughness augmentation using wearable vibrotactile haptics and a square wave signal to simulate a patterned texture: Our objective was not to accurately reproduce real textures, but to induce different perceived roughness on the same real surface with a well controlled parameters.
-However, more accurate models for simulating interaction with virtual textures should be applied to wearable haptic augmentations, such as in \textcite{unger2011roughness}.
+However, more accurate models for simulating interaction with virtual textures should be applied to wearable haptic augmentations \cite{unger2011roughness}.
 Another limitation that may have affected the perception of the haptic texture augmentations is the lack of compensation for the frequency response of the actuator and amplifier \cite{asano2012vibrotactile,culbertson2014modeling,friesen2024perceived}.
 %The dynamic response of the finger should also be considered, and may vary between individuals.
 
@@ -109,7 +110,7 @@ The visual hand renderings we evaluated were displayed on the Microsoft HoloLens
 We purposely chose this type of display as it is with \OST-\AR that the lack of mutual occlusion between the hand and the \VO is the most challenging to solve \cite{macedo2023occlusion}.
 We thus hypothesized that a visual hand rendering would be more beneficial to users with this type of display.
 However, the user's visual perception and experience is different with other types of displays, such as \VST-\AR, where the \RE view is seen through cameras and screens (\secref[related_work]{ar_displays}).
-While the mutual occlusion problem and the hand tracking latency can be overcome with \VST-\AR, the visual hand rendering could still be beneficial to users as it provides depth cues and feedback on the hand tracking, and should be evaluated as such.
+While the mutual occlusion problem and the hand tracking latency could be overcome with \VST-\AR, the visual hand rendering could still be beneficial to users as it provides depth cues and feedback on the hand tracking, and should be evaluated as such.
 
 \paragraph{More Ecological Conditions}
 
@@ -136,17 +137,45 @@ It remains to be explored how to support rendering for different and larger area
 
 \section{Perspectives}
 
+Our goal was to improve direct hand interaction with \VOs using wearable haptic devices in immersive \AR, by providing more plausible and coherent perception as well as more natural and effective manipulation of the visuo-haptic augmentations.
+Our contributions have enabled progress towards a seamless integration of the virtual into the real world.
+They also allow us to outline out longer-term research perspectives.
+
 \subsection*{Towards Universal Wearable Haptic Augmentation}
 
+We have reviewed how complex the sense of touch is (\secref[related_work]{haptic_hand}).
+Multiple sensory receptors all over the skin allow us to perceive different properties of objects, such as their texture, temperature, weight or shape.
+Particularly concentrated in the hands, their sensory feedback is crucial, along with the muscles, for grasping and manipulating objects.
+In this manuscript, we have shown how wearable haptic devices can provide virtual tactile sensations to support direct hand interaction in immersive \AR.
+In particular, we have investigated the visuo-haptic perception of texture augmenting real surfaces (\partref{perception}) as well as the manipulation of \VOs with visuo-haptic feedback of hand contacts with \VOs (\partref{manipulation}).
+
+However, unlike for the visual sense, which can be completely immersed in the virtual using an \AR/\VR headset, there is no universal wearable haptic device that can reproduce all the haptic properties perceived by the hand (\secref[related_work]{wearable_haptics}).
+Thus, the haptic renderings and augmentations we studied were limited to specific properties of roughness (\chapref{vhar_system}) and contact (\chapref{visuo_haptic_hand}) using vibrotactile feedback.
+A systematic and comparative study of existing wearable haptic devices and renderings should therefore be carried out to assess their ability to reproduce the various haptic properties \cite{culbertson2017importance,friesen2024perceived}.
+More importantly, the visuo-haptic coupling of virtual and augmented objects should be studied systematically, as we did for textures in \AR (\chapref{vhar_textures}) or as done in \VR \cite{choi2021augmenting,gunther2022smooth}.
+Attention should also be paid to the perceptual differences of wearable haptics in \AR \vs \VR (\chapref{xr_perception}).
+This would allow to assess the relative importance of visual and haptic feedback in the perception of object properties, and how visual rendering can support or compensate for limitations in wearable haptic rendering.
+
+One of the main findings of studies on the haptic perception of real objects is the importance of certain perceived properties over others in discriminating between objects \cite{hollins1993perceptual,baumgartner2013visual,vardar2019fingertip}.
+It would therefore be interesting to determine which wearable haptic renderings are most important for the perception and manipulation of virtual and augmented objects with the hand in \AR and \VR.
+User studies could then be conducted similarly, reproducing as many haptic properties as possible in \VO discrimination tasks.
+These results would make it possible to design more universal wearable haptic devices that provide rich haptic feedback that best meets users' needs for interaction in \AR and \VR.
+
 % systematic exploration of the parameter space of the haptic rendering to determine the most important parameters their influence on the perception
 % measure the difference in sensitivity to the haptic feedback and how much it affects the perception of the object properties
 
+\subsection*{Responsive Visuo-Haptic Augmented Reality}
+
+Nous avons vu la diversité des affichages de réalité augmentée et virtuelle ainsi que les implications sur le rendu des objets virtuel, sa perception (\secref[related_work]{ar_displays}) et sa manipulation avec la main (\chapref{visual_hand}).
+La diversité des dispositifs haptiques portables et des rendus tactiles qu'ils peuvent fournir est plus importante encore et un sujet de recherche actif (\secref[related_work]{wearable_haptics}).
+Le couplage de l'haptique portable avec la RA immersive demande aussi de placer l'haptique ailleurs sur le corps qu'aux points de contact de la main avec les objets virtuels (\secref[related_work]{vhar_haptics}).
+En particulier, nous avons étudié la perception d'augmentations haptiques de textures avec un dispositif vibrotactile sur la phalange médiane (\secref{vhar_system}) et comparés plusieurs positionnements de l'haptique sur la main pour la manipulation d'objets virtuels (\secref{visuo_haptic_hand}).
+
+Un rendu haptique fourni proche du point de contact de la main avec le virtuel semble donc préférable pour augmenter la perception d'objets réels (\secref{vhar_textures}) et améliorer la manipulation d'objets virtuels (\secref{visuo_haptic_hand}).
+%Given these three points, and the diversity of haptic actuators and renderings, one might be able to interact with the \VOs with any haptic device, worn anywhere on the body and providing personalized feedback on any other part of the hand, and the visuo-haptic system should be able to support such a adapted usage.
+% design, implement and validate procedures to automatically calibrate the haptic feedback to the user's perception in accordance to what it has been designed to represent
+% + let user free to easily adjust (eg can't let adjust whole spectrum of vibrotactile, reduce to two or three dimensions with sliders using MDS)
+
 %- Visio en réalité mixte : ar avec avatars distants, vr pour se retrouver dans l'espace de l'autre ou un espace distant, et besoin de se faire toucher des objets à distance
 %- Ou bien en cours, voir l'échantillon à toucher dans lenv de travail ou en contexte en passant en VR
 %- Ex : médecin palpation, design d'un objet, rénovation d'un logement (AR en contexte courant, VR pour voir et toucher une fois terminé)
-
-\subsection*{Responsive Visuo-Haptic Augmented Reality}
-
-%Given these three points, and the diversity of haptic actuators and renderings, one might be able to interact with the \VOs with any haptic device, worn anywhere on the body and providing personalized feedback on any other part of the hand, and the visuo-haptic system should be able to support such a adapted usage.s
-% design, implement and validate procedures to automatically calibrate the haptic feedback to the user's perception in accordance to what it has been designed to represent
-% + let user free to easily adjust (eg can't let adjust whole spectrum of vibrotactile, reduce to two or three dimensions with sliders using MDS)