\chapter{Related Work}
\mainlabel{related_work}

\chaptertoc

This chapter reviews previous work on the perception and manipulation directly with the hand of \AEs using \WHs, \AR and their combination.
Experiencing a visual, haptic, or visuo-haptic \AE relies on one to many interaction loops between a user and the environment, as shown in \figref[introduction]{interaction-loop}, and each main step must be addressed and understood: the tracking and modelling of the \RE into a \VE, the interaction techniques to act on the \VE, the rendering of the \VE to the user through visual and haptic user interfaces, and, finally, the user's perception and actions on the overall \AE.

To achieve this, we first describe how the hand senses and acts on its environment to perceive the haptic properties of real everyday objects.
Secondly, we present how \WH devices and renderings have been used to provide tactile feedback and enhance the touch interaction with virtual and augmented objects, with a focus on vibrotactile feedback and haptic textures.
Thirdly, we introduce the principles, implementations and user perception of \AR, and overview the main interaction techniques used to manipulate virtual and augmented objects.
Finally, we present how multimodal visual and haptic feedback have been combined in \AR to modify the user perception of tangible objects, and to improve the user interaction with \VOs.

\input{1-haptic-hand}
\input{2-wearable-haptics}
\input{3-augmented-reality}
\input{4-visuo-haptic-ar}
\input{5-conclusion}