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Complete related work

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Erwan Normand
2024-09-23 11:56:19 +02:00
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1-introduction/related-work/3-augmented-reality.tex
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@@ -23,21 +23,14 @@ Fixed to the ceiling, the headset displayed a stereoscopic (one image per eye) p
\subsubsection{A Definition of AR}
\label{ar_definition}
The system of \cite{sutherland1968headmounted} already fulfilled the first formal definition of \AR, proposed by \textcite{azuma1997survey} in the first survey of the domain:
\begin{enumerate}[label=(\arabic*)]
\item combine real and virtual,
\item be interactive in real time, and
\item register real and virtual\footnotemark.
\end{enumerate}
%\footnotetext{There quite confusion in the literature and in (because of) the industry about the terms \AR and \MR. The term \MR is very often used as a synonym of \AR, or a version of \AR that enables an interaction with the virtual content. The title of this section refers to the title of the highly cited paper by \textcite{speicher2019what} that examines this debate.}
\footnotetext{This third characteristic has been slightly adapted to use the version of \textcite{marchand2016pose}, the original definition was: \enquote{registered in \ThreeD}.}
The first formal definition of \AR was proposed by \textcite{azuma1997survey}: (1) combine real and virtual, (2) be interactive in real time, and (3) register real and virtual\footnotemark.
Each of these characteristics is essential: the real-virtual combination distinguishes \AR from \VR, a movie with integrated digital content is not interactive and a \TwoD overlay like an image filter is not registered.
There are also two key aspects to this definition: it does not focus on technology or method, but on the user's perspective of the system experience, and it does not specify a particular human sense, \ie it can be auditory \cite{yang2022audio}, haptic \cite{bhatia2024augmenting}, or even olfactory \cite{brooks2021stereosmell} or gustatory \cite{brooks2023taste}.
Yet, most of the research have focused on visual augmentations, and the term \AR (without a prefix) is almost always understood as \v-\AR.
\footnotetext{This third characteristic has been slightly adapted to use the version of \textcite{marchand2016pose}, the original definition was: \enquote{registered in \ThreeD}.}
%For example, \textcite{milgram1994taxonomy} proposed a taxonomy of \MR experiences based on the degree of mixing real and virtual environments, and \textcite{skarbez2021revisiting} revisited this taxonomy to include the user's perception of the experience.
@@ -70,16 +63,16 @@ Yet, the user experience in \AR is still highly dependent on the display used.
\label{ar_displays}
To experience a virtual content combined and registered with the \RE, an output \UI that display the \VE to the user is necessary.
There is a large variety of \AR displays with different methods of combining the real and virtual content (\VST, \OST, or projected), and different locations on the \RE or the user \cite{billinghurst2015survey}.
There is a large variety of \AR displays with different methods of combining the real and virtual content, and different locations on the \RE or the user \cite{billinghurst2015survey}.
In \VST-\AR, the virtual images are superimposed to images of the \RE captured by a camera \cite{marchand2016pose}, and the combined real-virtual image is displayed on a screen to the user, as illustrated in \figref{itoh2022indistinguishable_vst}, \eg \figref{hartl2013mobile}.
In \emph{\VST-\AR}, the virtual images are superimposed to images of the \RE captured by a camera \cite{marchand2016pose}, and the combined real-virtual image is displayed on a screen to the user, as illustrated in \figref{itoh2022indistinguishable_vst}, \eg \figref{hartl2013mobile}.
This augmented view through the camera has the advantage of a complete control on the real-virtual combination such as mutual occlusion between real and virtual objects \cite{macedo2023occlusion}, coherent lighting and no delay between the real and virtual images \cite{kruijff2010perceptual}.
But, due to the camera and the screen, the user's view is degraded with a lower resolution, frame rate, field of view, and an overall visual latency compared to proprioception \cite{kruijff2010perceptual}.
An \OST-\AR directly combines the virtual images with the real world view using a transparent optical system \cite{itoh2022indistinguishable} to like augmented glasses, as illustrated in \figref{itoh2022indistinguishable_ost}, \eg \figref{lee2013spacetop}.
An \emph{\OST-\AR} directly combines the virtual images with the real world view using a transparent optical system \cite{itoh2022indistinguishable} to like augmented glasses, as illustrated in \figref{itoh2022indistinguishable_ost}, \eg \figref{lee2013spacetop}.
These displays feature a direct, preserved view of the \RE at the cost of more difficult registration (spatial misalignment or temporal latency between the real and virtual content) \cite{grubert2018survey} and mutual real-virtual occlusion \cite{macedo2023occlusion}.
Finally, projection-based \AR overlay the virtual images on the real world using a projector, as illustrated in \figref{roo2017one_2}, \eg \figref{roo2017inner}.
Finally, \emph{projection-based \AR} overlays the virtual images on the real world using a projector, as illustrated in \figref{roo2017one_2}, \eg \figref{roo2017inner}.
It doesn't require the user to wear the display, but requires a real surface to project the virtual on, and is vulnerable to shadows created by the user or the real objects \cite{billinghurst2015survey}.
\begin{subfigs}{ar_displays}{Simplified operating diagram of \AR display methods. }[
@@ -94,9 +87,9 @@ It doesn't require the user to wear the display, but requires a real surface to
\end{subfigs}
Regardless the \AR display, it can be placed at different locations \cite{bimber2005spatial}, as shown in \figref{roo2017one_1}.
Spatial \AR is usually projection-based displays placed at fixed location (\figref{roo2017inner}), but it can also be \OST or \VST fixed windows (\figref{lee2013spacetop}).
Alternatively, \AR displays can be hand-held, like a \VST smartphone (\figref{hartl2013mobile}), or body-attached, like a micro-projector used as a flashlight \cite{billinghurst2015survey}.
Finally, \AR displays can be head-worn like \VR headsets or glasses, providing a highly immersive and portable experience.
\emph{Spatial \AR} is usually projection-based displays placed at fixed location (\figref{roo2017inner}), but it can also be \OST or \VST \emph{fixed windows} (\figref{lee2013spacetop}).
Alternatively, \AR displays can be \emph{hand-held}, like a \VST smartphone (\figref{hartl2013mobile}), or body-attached, like a micro-projector used as a flashlight \cite{billinghurst2015survey}.
Finally, \AR displays can be head-worn like \VR \emph{headsets} or glasses, providing a highly immersive and portable experience.
%Smartphones, shipped with sensors, computing ressources and algorithms, are the most common \AR today's displays, but research and development promise more immersive and interactive \AR with headset displays \cite{billinghurst2021grand}.
\fig[0.75]{roo2017one_1}{Locations of \AR displays from eye-worn to spatially projected. Adapted by \textcite{roo2017one} from \textcite{bimber2005spatial}.}