Intro VR input

diff --git a/tex/3-input.tex b/tex/3-input.tex
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--- a/tex/3-input.tex
+++ b/tex/3-input.tex
@@ -685,24 +685,49 @@ Il the case of our command selection technique for multi-touch interaction with
 Therefore, the location of the contact point does not matter.
 Hence, users can touch the surface with a comfortable posture.
 
-\subsection{Interaction in immersive Virtual Reality}
+\subsection{Input in immersive Virtual Reality}
 \label{sec:interactionvr}
 
 Immersive virtual reality has been around since the beginning of personal computing \cite{sutherland65,sutherland68}.
 Early prototypes already included a stereovision headset with head tracking to match the users' movements with their position in the virtual environment.
-Yet, it took much longer to reach either households or professional environments than personal computers.
-Even today that many different consumer electronics VR headsets are available at reasonnable price, their usage remains limited.
-Virtual Reality is an active research domain in itself for decades, and it contributed to the relative success of the last generation of VR headsets.
-But more research is still necessary to discover the benefits and best way to interact in immersive virtual environments.
-One big research topic in this area is augmenting \defword{immersion}, \defword{presence} and \defword{embodiment} \cite{witmer98,slater99,kilteni12}.
-In short these three concept are related to the users's sensation of being in the virtual environment.
+Yet, it took VR headsets much longer than personal computers to reach either households or professional environments.
+Even today that many different consumer electronics VR headsets are available at a reasonnable price, their usage remains limited.
+Similarly to every interactive technology, the objective is not to replace completely concurrent technologies, but rather find the particular application scenarios for which this technology is more suitable than others.
+
+%Virtual Reality is an active research domain in itself for decades, and immersive virtual reality is just a subset of the contexts being studied.
+%Yet, this research field contributed to the relative success of the last generation of VR headsets.
+%However, more research is still necessary to discover the benefits and best ways to interact in immersive virtual environments.
+The studies I will describe in this section focus on input methods for immersive virtual reality.
+We take immersive virtuality reality as a context that constrains the input methods we can use, in which users have to perform specific tasks.
+One of these constraints is that the users cannot see their own body because the virtual environment covers their entire field of view.
+Therefore, either a motion capture system sense the users' body movements, or they hold input devices in their hands.
+Users interact with their environment mostly with gestures, but also with buttons, touchpads and joysticks on handheld devices.
+As we discussed at the beginning of this chapter, the objective in virtual reality is not necessarily to reproduce what exists in the physical world.
+We rather focus on either elementary or compound tasks and figure out ways to enable users to perform these tasks.
+For example selecting an object is an elementary task that is usually part of a more complex or compound tasks: manipulation, command selection, navigation, text entry, etc.
+We describe below the design and evaluation of a new 3D selection technique for immersive virtual reality.
+
+% Should I keep this?
+One of the main active research topics in this area is augmenting \defword{immersion}, \defword{presence} and \defword{embodiment} \cite{witmer98,slater99,kilteni12}.
+In short, these three concepts are related to the users's sensation of being in the virtual environment.
 I will cover this topic in the next chapter, section \ref{sec:embodiment}.
+%
+Yet, a typical way to increase the users' sensation of embodiment is to provide them an \defword{avatar} that they can control.
+The users can typically control their avatar's hands and head because it is easy to map their position to the VR headset and the controller’s position with inverse kinematics.
+The facial expression of the avatar is important for non verbal communication.
+However, it is more complex to control because it requires many degrees of freedom
+Therefore we describe below the design and evaluation of an interaction technique for the control of the facial expression of an avatar in immersive virtual environments.
 
-this work is about interaction above all, VR is a context of use.
-
-methodology: identify design aspects, evaluate alternatives, then build a combination of the best, then compare with the best of literature
+We used a common general methodology for the design of these two interaction techniques.
+We identified the key design aspects of the techniques and we implemented and evaluated several alternatives.
+Then we implemented the best combination of these alternatives and compared it to equivalent techniques in the literature.
 
 \subsubsection{Pointing}
+
+In the physical world it is difficult to interact with objects remotely because of physical constraints.
+In virtual worlds such physical constraints do not exist.
+The common technique for selecting objects…
+
 RayCursor \cite{baloup19,baloup18,baloup19a}
 
 \begin{figure}[htb]
@@ -745,6 +770,8 @@ Leverages 3D input and combines with 3D motion for more efficient pointing
 Non verbal communication
 Facial expressions \cite{baloup21}
 
+task decomposition \cite{bowman04}
+
 \begin{figure}[htb]
   \def\fh{3.7cm}
   a)