\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, this chapter first gives an overview of the haptic sense, and how \WH devices and renderings have been used to provide tactile feedback to enhance the touch perception and interaction with virtual and augmented objects, with a focus on vibrotactile feedback and haptic textures.
%
Secondly, it introduces the principles and user perception of \AR, and describes the interaction techniques used in \AR and \VR environments to interact with virtual and augmented objects, in particular using the visual rendering of the user's hand.
%
Finally, it presents how multimodal visual and haptic feedback have been combined in \AR to modify the user perception, in particular when touching a tangible, and to improve the user interaction with the augmented environment, in particular when manipulating \VOs.

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