\chapterstartoc{Abstract}

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% Wearable Visuo-Haptic Rendering in Augmented Reality
% Direct Hand Perception and Interaction with Visuo-Haptic Augmented Reality
% Enhancing the Perception and Interaction with Visuo-Haptic Augmented Reality
% Interaction and Perception in Visuo-Haptic Augmented Reality using Wearable Vibrotactile Devices
% Enhancing the User Experience with Wearable Visuo-Haptic Rendering in Augmented Reality

Wearable haptic devices provide tactile sensations to the skin in a portable and unobtrusive way. %, to render haptic feedback of virtual objects.
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Their use has been little explored in augmented reality (AR), where virtual content is integrated into real world perception.
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%They have been used to render rich and various haptic feedback to virtual object in virtual reality (VR) or to augment the perception of a real object being touched.
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In this thesis, we investigate the integration of wearable haptic devices with AR in the context of direct hand interaction with virtual and augmented objects.
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We consider two axes of research: (I) providing plausible and coherent visuo-haptic texture augmentations, and (II) improving virtual object interaction with visuo-haptic augmentation of the hand.

First, we study how visual rendering affects the perception of virtual vibrotactile textures that augment real surfaces directly touched by the finger.
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To this end, we propose (1) a system for rendering visuo-haptic virtual texture augmentations using an AR headset and a wearable vibrotactile device. We then (2) evaluate how the roughness perception of virtual haptic textures differs in AR \vs virtual reality (VR) and when touched by a virtual hand \vs one's own hand. Finally, we (3) investigate the realism, plausibility and coherence of combining visual and haptic texture augmentations in AR.

Secondly, we investigate how the visuo-haptic rendering of the hand improves its direct manipulation of virtual objects in AR in terms of performance and user experience.
% address the challenge of manipulating virtual objects directly with the hand in AR, which is a key interaction but is still challenging due to visual and haptic limitations.
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We first (1) explore the effect of six visual renderings of the hand that provide contact feedback with the virtual object.
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We then (2) evaluate two vibrotactile contact techniques, provided at four different locations on the real hand, and compared to the two most representative visual hand renderings from the previous contribution.