The squeeze film effect uses a high-frequency signal (tens of thousand Hertz) that we cannot perceive directly.{}
This vibration creates an air cushion between the finger and the surface so that this surface feels smoother~\cite{biet07}.
-Finally, there are non-contact tactile technologies that transmit tactile feedback through air.
+Finally, there are non-contact tactile technologies that transmit tactile feedback through the air.
One technique uses an array of ultrasound actuators.
The interferences of ultrasound waves create a stress field that triggers the sense of touch~\cite{hoshi10,carter13}
Another technique uses air vortexes~\cite{guptas13,sodhi13}.
-The displacement of a large membrane inside a box moves the air inside, which can escape trough a small circular hole.
-The vortex is created with the pressure, and moves forward on several meters before dissipating.
+The displacement of a large membrane inside a box moves the air inside, which can escape through a small circular hole.
+The vortex is created with the pressure and moves forward on several meters before dissipating.
\paragraph{Sense of touch}
The objective when producing a physical effect with a haptic system is to stimulate the users' sense of touch.
On \reffig{fig:hapticpath}, I separate the pure sensing part from the interpretation part.
-The body has sensors in the skin, muscles, tendons and articulations~\cite{bolanowski88}.
-These sensors are different type of nerves and similarly to electronic sensors they transform physical effects into electric signals.
+The body has sensors in the skin, muscles, tendons, and articulations~\cite{bolanowski88}.
+These sensors are different type sof nerves and similarly to electronic sensors, they transform physical effects into electric signals.
This document will not cover this in detail.
The interested reader will find explanations in many Ph.D. manuscripts about haptics~\cite{brown07,crossan03,hoggan10,oakley03}, including mine~\cite{pietrzak08}.
We will just mention cornerstone studies about the perception of touch that established the limits of tactile perception~\cite{goff67}, which depend on the body part, sex, and laterality~\cite{weinstein68}.
-In particular, authors established the range of frequencies humans can perceive (roughly up to 1000Hz), with a peak perception around 250Hz.
-This study is the motivation why most of vibrotactile systems use a 250 Hz signal, sometimes modulated with another frequency~\cite{brown06}.
+In particular, the authors established the range of frequencies humans can perceive (roughly up to 1000Hz), with a peak perception around 250Hz.
+This study is the motivation why most vibrotactile systems use a 250 Hz signal, sometimes modulated with another frequency~\cite{brown06}.
My opinion on this choice is that other frequencies provide different and interesting sensations.
They just require a higher amplitude to be perceivable.
However, the amplitude produced with usual vibrotactile systems is sufficient for a large range of frequencies.
-%This is not necessarily an issue on a design point of view because high amplitude vibrations are uncomfortable anyway.
+%This is not necessarily an issue from a design point of view because high amplitude vibrations are uncomfortable anyway.
This is why we typically used different frequencies in our studies~\cite{gupta16,gupta17}.
The perception of touch is nevertheless not only a matter of received signal.
The amplitude of the signal on both actuators is a ratio corresponding to the desired position of the virtual vibration.
For example, let $A$ be the maximum amplitude and two actuators $a$ and $b$ placed $4cm$ apart, as depicted on the left part of \reffig{fig:illusions}.
If the amplitude of actuator $a$ is $A(a) = \frac{A}{4}$ and the amplitude of actuator $b$ is $A(b) = \frac{3A}{4}$, then the users feel a vibration between $a$ and $b$, $1cm$ away from $a$ and $3cm$ away from $b$.
-Tactile saltation, also called the cutaneous rabbit illusion, gives the illusion of a sequence of equally spaced vibration~\cite{geldard72}.
+Tactile saltation (also called the cutaneous rabbit illusion) gives the illusion of a sequence of equally spaced vibration~\cite{geldard72}.
The tactile stimulation however is a repeated vibration on a smaller subset of locations.
For example, with three actuators $a$, $b$, and $c$ equally spaced on a straight line, the stimulation is three vibrations on $a$, three on $b$, and three on $c$, as shown on the right part of \reffig{fig:illusions}.
The person feels nine equally spaced stimulations between $a$ and $c$.
-Israr \etal combined both funneling and saltation to produce 2D tactile motions, not only in straight line but also on curves~\cite{israr11}.
+Israr \etal combined both funneling and saltation to produce 2D tactile motions, not only in a straight line but also on curves~\cite{israr11}.
\section{Research questions}
The haptic rendering pipeline described above illustrates the multidisciplinary aspect of such research.
It also reveals the many pitfalls at all levels that can make users perceive something different than what was intended.
Any step in this pipeline potentially introduces a drift with respect to the original message.
-For example the resolution of commands could be too low, the mechanical response to the command can be non-linear, the quality of the contact between the haptic system and the user can be sub-optimal, the mechanical effects can be out of the perceptual range, and haptic illusions can alter the interpretation of sensations.
-While the work of researchers in specialized domains mentioned in \reffig{fig:hapticpath} is to avoid, or at least minimize such drifts in their part of the pipeline, my work as an HCI researcher consists in selecting, adjusting, combining, designing, implementing and evaluating such parts to build \defword{interactive systems}.
-My research is therefore fundamentally interdisciplinary, and I combine, complement or replace expertise of different domains, depending of the needs of each research project, and the expertise of my collaborators.
+For example, the resolution of commands could be too low, the mechanical response to the command can be non-linear, the quality of the contact between the haptic system and the user can be sub-optimal, the mechanical effects can be out of the perceptual range, and haptic illusions can alter the interpretation of sensations.
+While the work of researchers in specialized domains mentioned in \reffig{fig:hapticpath} is to avoid, or at least minimize such drifts in their part of the pipeline, my work as an HCI researcher consists in selecting, adjusting, combining, designing, implementing, and evaluating such parts to build \defword{interactive systems}.
+My research is therefore fundamentally interdisciplinary, and I combine, complement or replace the expertise of different domains, depending on the needs of each research project, and the expertise of my collaborators.
My objective is to make interactive systems better than the sum of their parts.
%I prefer the term “interactive system” over “interface” because it better conveys my systemic approach.
\subsection{Output vocabulary}
-On a practical point of view, when a new haptic technology emerges, their designers need information about their specifications: the size of actuators, voltage, required amplitude, resonant frequency, maximum force (continuous and peak), etc.
-They often simulate the behavior of their actuators, and evaluate the relation between the command and the physical effect~\cite{poncet17,poncet16}.
-However, they need to know the desired parameters and values of the physical effects they can produce in order to propose a suitable output vocabulary .
+From a practical point of view, when a new haptic technology emerges, their designers need information about their specifications: the size of actuators, voltage, required amplitude, resonant frequency, maximum force (continuous and peak), etc.
+They often simulate the behavior of their actuators and evaluate the relation between the command and the physical effect~\cite{poncet17,poncet16}.
+However, they need to know the desired parameters and values of the physical effects they can produce in order to propose a suitable output vocabulary.
Therefore we perform iterations of prototyping and evaluation of human factors in order to understand these requirements, and design \defword{interaction techniques}.
%Interactive systems are made of \defword{interaction techniques}, which
-Interaction techniques are combinations of a device (part of the electro-machanical system) and an interactive language (part of the software controller)~\cite{nigay95}.
-%Users interact with \fixme{digital} systems with \defword{interaction techniques}, which are combinations of a device (part of the electro-machanical system) and an interactive language (part of the software controller)~\cite{nigay95}.
+Interaction techniques are combinations of a device (part of the electro-mechanical system) and an interactive language (part of the software controller)~\cite{nigay95}.
+%Users interact with \fixme{digital} systems with \defword{interaction techniques}, which are combinations of a device (part of the electro-mechanical system) and an interactive language (part of the software controller)~\cite{nigay95}.
%Devices are usually computer peripherals, we presented some of them previously.
We presented technologies for haptic devices above.
Interactive languages are systematic descriptions of the inputs and outputs of an interactive device.
Similar to programming languages, they have three levels: lexical, syntactic, and semantic.
-\begin{figure}[b]
+\begin{figure}[htb]
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+ \def\sx{1mm}
+ \def\sy{0.4mm}
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+ \draw[x=\sx,y=\sy, ultra thick]
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\node[x=1mm,y=1mm, anchor=center] () at (68,-9){Amplitude};
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+ \draw[x=\sx,y=\sy, ultra thick]
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\node[x=1mm,y=1mm, anchor=center] () at (112,-9){Duration};
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+ \draw[x=\sx,y=\sy, xshift=140mm, ultra thick]
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(12,0);
- \draw[x=1mm,y=0.5mm, xshift=155mm, ultra thick]
+ \draw[x=\sx,y=\sy, xshift=155mm, ultra thick]
(0,0) -- (0,10) -- (2,10) -- (2,-10) --
(4,-10) -- (4,10) -- (6,10) -- (6,-10) --
(8,-10) -- (8,10) -- (10,10) -- (10,-10) --
The \emph{lexical level} defines the basic vocabulary of the device.
For example, we can control vibrations in frequency, amplitude, shape, and duration (\reffig{fig:lexical}).
Hence the command for a vibrotactile actuator is an electrical signal made of these elements.
-The research challenge here is to bridge the knowledge gap between the engineering of actuators and human factors, and find tactile parameters that users can perceive and distinguish.
+The research challenge here is to bridge the knowledge gap between the engineering of actuators and human factors to find tactile parameters that users can perceive and distinguish.
Such research is typically useful to guide the design of tactile actuators.
We will illustrate this kind of research in section~\ref{sec:stimtac}.
%Hence, a software controller sends three values to the electro-mechanical system, which will convert it to forces.
%Such devices also have an input vocabulary, typically 3DOF or 6DOF (translations + rotations) and sometimes one or several buttons.
-The \emph{syntactic level} combines lexical items to form haptic phrases.
-They eventually combine different modalities.
-%, into higher level representations.
-The \reffig{fig:syntactic} shows several examples of such haptic phrases with vibrotactile feedback.
-Frequency and amplitude modulation create new kinds of feedback, that Brown \etal describe as roughness \cite{brewster04}.
-They also use sequences of vibrations to form rhythms.
-The challenge here is to find combinations of parameters that users are able to interpret together.
-I conducted such kind of research during my Ph.D.~\cite{pietrzak05, pietrzak05a, pietrzak06, pietrzak09}.
-The difficulty is not only to identify such haptic parameters but also to evaluate them.
-By increasing the number of parameters and the number of values for each parameter, we quickly reach a point where it is impossible to evaluate every combination.
-In this case, we use other methods that basically consist of probing this space.
-We will discuss this in section~\ref{sec:stimtac}.
-
-%Typically, force-feedback device use force models, as described in the previous section.
-%These are functions that compute forces depending on the device's position.
-%For example, there are force models for springs, magnets, damping or other kinds of forces.
-
\begin{figure}[htb]
\tikzexternalenable
+\def\sx{1mm}
+\def\sy{0.4mm}
\begin{tikzpicture}
%\draw[loosely dotted] (0,-1) grid (17,1);
- \draw[x=0.5mm,y=0.5mm, ultra thick]
+ \draw[x=0.5mm,y=\sy, ultra thick]
(0,0) sin (5,10) cos (10,0) sin (14,-10) cos
(18,0) sin (21,10) cos (24,0) sin (26,-10) cos
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(52,0) sin (57,10) cos (62,0);
\node[x=1mm,y=1mm, anchor=center] () at (18,-13){Frequency modulation};
- \draw[x=1mm,y=0.5mm, xshift=71mm, ultra thick]
+ \draw[x=\sx,y=\sy, xshift=71mm, ultra thick]
(0,0) sin (1,5) cos (2,0) sin (3,-5) cos
(4,0) sin (5,7) cos (6,0) sin (7,-7) cos
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(28,0);
\node[x=1mm,y=1mm, anchor=center] () at (84,-13){Amplitude modulation};
- \draw[x=0.5mm,y=0.5mm, xshift=140mm, ultra thick]
+ \draw[x=0.5mm,y=\sy, xshift=140mm, ultra thick]
(0,0) sin (1,10) cos (2,0) sin (3,-10) cos
(4,0) sin (5,10) cos (6,0) sin (7,-10) cos
(8,0) sin (9,10) cos (10,0) sin (11,-10) cos
\label{fig:syntactic}
\end{figure}
+The \emph{syntactic level} combines lexical items to form haptic phrases.
+They eventually combine different modalities.
+%, into higher level representations.
+The \reffig{fig:syntactic} shows several examples of such haptic phrases with vibrotactile feedback.
+Frequency and amplitude modulation create new kinds of feedback, that Brown \etal describe as roughness \cite{brewster04}.
+They also use sequences of vibrations to form rhythms.
+The challenge here is to find combinations of parameters that users are able to interpret together.
+I conducted such kind of research during my Ph.D.~\cite{pietrzak05, pietrzak05a, pietrzak06, pietrzak09}.
+The difficulty is not only to identify such haptic parameters but also to evaluate them.
+By increasing the number of parameters and the number of values for each parameter, we quickly reach a point where it is impossible to evaluate every combination.
+In this case, we use other methods that basically consist of probing this space.
+We will discuss this in section~\ref{sec:stimtac}.
+
+%Typically, force-feedback device use force models, as described in the previous section.
+%These are functions that compute forces depending on the device's position.
+%For example, there are force models for springs, magnets, damping or other kinds of forces.
+
The \emph{semantic level} represents the mapping between the haptic effect and its associated meaning.
For example, if we create Tactons for meeting alerts, we can encode the kind of meeting with a rhythm, the importance with roughness, and the delay with spatial location.
The combination of both parameters enables encoding every level of urgency for every caller ID.
\centering
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\definecolor{cellblue}{rgb} {0.17,0.60,0.99}
-
+ %
\newcommand{\labelcell}[2]{
\node[minimum width=1.0cm, minimum height=.75cm,text width=3.0cm, align=center, outer sep=0, column sep=0cm](#1) {\textbf{#2}};
}
\end{tikzpicture}
\tikzexternaldisable
- \caption[Mapping information with Tactons.]{Illustration of a semantic mapping between 3-parameters Tactons and a 3-level information, adapted from~\cite{brown06}. Three values of rhythm are mapped to three types of messages, three values of roughness are mapped to three degrees of importance, and three spatial locations are mapped to three values of delay.}
+ \caption[Mapping information with Tactons.]{Illustration of a semantic mapping between 3-parameters Tactons and a 3-level information, adapted from~\cite{brown06}. 3 values of rhythm are mapped to 3 types of messages, 3 values of roughness are mapped to 3 degrees of importance, and 3 spatial locations are mapped to 3 values of delay.}
\label{fig:semantic}
\end{figure}
We described above the design rationale and pitfalls of such systems.
Beyond these haptic systems, physical objects have their own haptic properties.
They have a weight, mobile parts with resistance, tactile textures, etc.
-For example, physical buttons provide haptic click and detents sensations.
+For example, physical buttons provide a haptic click and detents sensations.
These haptic properties are structural and mechanical.
-For example the size, shape and layout of keyboard keys, as well as the keyboard slope, height, and profile are carefully designed~\cite{lewis97}.
+For example, the size, shape, and layout of keyboard keys, as well as the keyboard slope, height, and profile are carefully designed~\cite{lewis97}.
The mechanical force required to push the keys and the click sensation are also systematically adjusted.
The objective is to reduce the effects of fatigue and muscle strain, avoid incidental activations, and give immediate feedback to the user's action on the device.
-The haptic properties of physical interfaces is however typically missing on multi-touch interfaces.
+The haptic properties of physical interfaces are however typically missing on multi-touch interfaces.
Every widget feels like a flat surface.
Efforts were made to restore this missing haptic feedback.
-For example vibrotactile actuators can reproduce the clicking sensation of buttons~\cite{nashel03,lylykangas11}.
+For example, vibrotactile actuators can reproduce the clicking sensation of buttons~\cite{nashel03,lylykangas11}.
Several variable friction technologies can reproduce texture sensations~\cite{amberg11,bau10,levesque11}.
Not only this haptic feedback improves subjective assessment of comfort, but it also improves performance in some cases.
The clicking sensation on the Apple Magic Trackpad is impressive.
The haptic aspect of our interaction with everyday objects is richer than with interactive systems.
All the objects in our environment have haptic properties, and the design of these objects leverage these properties.
We can identify the key on the door on a keyring in our pocket, just by touch.
-Thanks to the tactile sensitivity of our fingers we can perceive the shape, size and material of the key to some extent.
+Thanks to the tactile sensitivity of our fingers we can perceive the shape, size, and material of the key to some extent.
We can identify ripe fruits and vegetables based on their hardness.
We can use a TV remote in the dark because we locate the keys with proprioception.
-We can tell if an opaque bottle is empty, full or in between because we feel its weight, and we can feel the liquid splashing inside.
+We can tell if an opaque bottle is empty, full ,or in between because we feel its weight, and we can feel the liquid splashing inside.
To leverage these haptic properties of everyday objects, there is indeed a compelling intersection with \defword{tangible interaction}.
Ullmer and Ishii described Tangible User Interfaces (TUI) this way: “TUIs will augment the real physical world by coupling digital information to everyday physical objects and environments.”~\cite{ishii97}.
Tangible interaction not necessarily focuses on haptic properties.
-However the fact that TUIs use everyday objects means that TUIs inherit their haptic properties.
-Further, physical objects have interesting properties, among which the possiblity to change their shape.
+However, the fact that TUIs use everyday objects means that TUIs inherit their haptic properties.
+Further, physical objects have interesting properties, among which the possibility to change their shape.
They can fold, squeeze, some parts are mobile.
Changing the shape of objects can change the way we use them, therefore their function.
For example, changing the shape of a knob changes the way we grip it~\cite{michelitsch04}.
The idea was to design haptic feedback for activity monitoring.
Fitness trackers became mainstream in the last decade.
People use wearable devices such as smartwatches or bracelets to measure their activities, such as their daily steps~\cite{consolvo08}.
-They typically define daily objectives, and need regular reminders to help them meeting their goal.
+They typically define daily objectives and need regular reminders to help them meet their goal.
These activity trackers provide visual information with small screens or LEDs.
-Therefore users have to actively look at their device to know their progress.
-This is a limitation of the incentive aspect of activity moitoring towards behavior change.
+Therefore users have to actively look at their devices to know their progress.
+This is a limitation of the incentive aspect of activity monitoring towards behavior change.
Still today, the solution in consumer electronics products is a simple vibration that encourages users to look at their device to check for information visually.
In this project we decided to provide progress information with vibrotactile feedback, thus not requiring users to look at the device while they perform their daily activities.
We describe below the design and evaluation of these Tactons.
\subsubsection{Tacton design}
-The context of activity monitoring implies several limitation on the design of the Tactons.
+The context of activity monitoring implies several limitations on the design of the Tactons.
We believed it would be difficult for us to motivate activity manufacturers to include a better tactile actuator than the existing ones.
Therefore we decided to use an off-the-shelf smartwatch: the Pebble\footnote{\href{https://en.wikipedia.org/wiki/Pebble_(watch)}{https://en.wikipedia.org/wiki/Pebble\_(watch)}}.
It includes an eccentric rotating mass (ERM) actuator.
-This low-resolution DC motor constrains the choice of tactile parameters to amplitude, duration and rhythm.
+This low-resolution DC motor constrains the choice of tactile parameters to amplitude, duration, and rhythm.
Given that the perception of amplitude varies from one user to another or the way the smartwatch is fastened, we use the duration and rhythm parameters only.
\paragraph{Information}
%%From Activibe
ActiVibe was designed as a set of vibrotactile icons to represent progress.
-As activity performace is generally evaluated as a percentage or as a value on a scale, we created vibrations corresponding to the values 1 to 10, with the objective of representing 10\% increments.
+As activity performance is generally evaluated as a percentage or as a value on a scale, we created vibrations corresponding to the values 1 to 10, intending to represent 10\% increments.
Because of our choice of using a single basic vibration actuator, we encode the vibrations using the duration and rhythm parameters only.
Since there was no prior encoding of discrete numbers found in the literature using duration and rhythm only, we first had to determine the best encoding pattern for ActiVibe.
%We designed a total of six patterns (\reffig{fig:activibesets}) and in our subsequent evaluations used the pattern with the highest accuracy rate for ActiVibe.
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\def\s{0.03}
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+ \node[x=1mm,y=1mm, anchor=center] () at (14,\labely){Set B};
\foreach \x in {1,...,10}
{
- \begin{scope}[yshift=(-(\x-1)*10)]
+ \begin{scope}[yshift=(-(\x-1)*\nl)]
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\begin{scope}[xshift=6cm] %Set C
- \node[x=1mm,y=1mm, anchor=center] () at (14,-36){Set C};
+ \node[x=1mm,y=1mm, anchor=center] () at (14,\labely){Set C};
\foreach \x in {1,...,10}
{
- \begin{scope}[yshift=(-(\x-1)*10)]
+ \begin{scope}[yshift=(-(\x-1)*\nl)]
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\sine{\s}{.10}{\l}
}
\end{scope}
\begin{scope}[xshift=9cm] %Set D
- \node[x=1mm,y=1mm, anchor=center] () at (14,-36){Set D};
+ \node[x=1mm,y=1mm, anchor=center] () at (14,\labely){Set D};
\foreach \x in {10,...,1}
{
- \begin{scope}[yshift=(-(10-\x)*10)]
+ \begin{scope}[yshift=(-(10-\x)*\nl)]
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\begin{scope}[xshift=\m mm]
}
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\begin{scope}[xshift=12cm] %Set E
- \node[x=1mm,y=1mm, anchor=center] () at (14,-36){Set E};
+ \node[x=1mm,y=1mm, anchor=center] () at (14,\labely){Set E};
\foreach \x in {1,...,10}
{
- \begin{scope}[yshift=(-(\x-1)*10)]
+ \begin{scope}[yshift=(-(\x-1)*\nl)]
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\pgfmathsetmacro{\m}{\y*\s*80}
\begin{scope}[xshift=\m mm]
}
\end{scope}
\begin{scope}[xshift=15cm] %Set F
- \node[x=1mm,y=1mm, anchor=center] () at (14,-36){Set F};
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\foreach \x in {1,...,4}
{
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- \begin{scope}[yshift=(-\xx*10)]
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- \begin{scope}[yshift=-40]
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\sine{\s}{.10}{8}
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\foreach \x in {1,...,4}
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- \begin{scope}[yshift=(-(\x+4)*10)]
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\foreach \y in {1,...,\x}
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- \begin{scope}[yshift=-90]
+ \begin{scope}[yshift=-9*\nl]
\sine{\s}{.10}{8}
\begin{scope}[xshift=32]
\sine{\s}{.10}{8}
\paragraph{Design Rationale}
Our design is driven by the semantics of the values we want to convey.
-Our intent is to represent discrete values of a progression.
+We intend to represent discrete values of a progression.
We explored two possibilities: 1) represent the actual value only; 2) represent the value as well as the scale.
%\paragraph{Duration Only}
In set A, each value is represented by a series of short pulses, separated by short pauses.
In set B, a continuous vibration represents each value with the duration corresponding to the value.
+\newpage
+
The disadvantage of representing only the value is that even if the user has an idea of the current value, there is no clue about the distance between this value and the maximum value.
Introducing a scale enables the positioning of a value relative to the beginning and the end of a progression.
Sets C-E represent both the value and the scale of a progression in several ways.
We were interested in knowing which sets of icons were most suitable for representing progression values, and what is the best precision we can obtain using these representations.
We can clearly see that we did not explore all the possible combinations.
This is mostly due to the limited number of sets we could reasonably evaluate in a laboratory study.
-Other dimensions are also be relevant, like adding a warning vibration before the actual code, to help users paying attention to the signal while doing their daily activities.
-However in some cases, the padding vibration more or less play this role.
-In any case we analyzed this aspect in the longitudinal study.
+Other dimensions are also relevant, like adding a warning vibration before the actual code, to help users paying attention to the signal while doing their daily activities.
+However, in some cases, the padding vibration more or less plays this role.
+In any case, we analyzed this aspect in the longitudinal study.
\paragraph{Parameter values}
In the longitudinal study, we increased the vibrations durations given that participants will not be paying as much attention to the vibration as they had in the laboratory studies.
Short vibration lasted $150ms$, long vibration $600ms$, and pauses were $200ms$ long.
-Finally, the pre-vibration were long vibrations of $700ms$.
+Finally, the pre-vibration was long vibrations of $700ms$.
\subsubsection{Evaluation}
I will not give the details about the evaluations in this study.
I will rather discuss the main findings with hindsight.
-Readers interested in the details about the experiment protocols and the results should refer to \cite{cauchard16}.
+Readers interested in the details about the experimental protocols and the results should refer to \cite{cauchard16}.
\paragraph{Counting VS duration}
The first findings are related to the participants' strategy for interpreting the patterns.
-Either they counted the short vibrations, or estimated the duration of the long ones.
-The results showed that it is easier to count vibrations than estimating the duration.
+Either they counted the short vibrations or estimated the duration of the long ones.
+The results showed that it is easier to count vibrations than to estimate the duration.
This is at least true within the tested range: 1-10, and $3s$ maximum.
Indeed, we believe it would be much more complicated to keep the count with higher values.
Durations are much complex to interpret, in particular because of the perception of time.
Now, sets C-E contained both short and long vibrations that potentially both encoded the target number.
Participants clearly stated that they counted the short vibrations to identify the answer.
-Therefore, with set D in which the sequence of small vibrations was a padding before the long vibration supposedly representing the answer, participants reported counting backwards.
+Therefore, with set D in which the padding sequence of small vibrations before the long vibration supposedly represented the answer, participants reported counting backward.
The set F was designed after the first user study.
The rationale was to reduce the counting task by using a long vibration for marking 5, and additional short vibrations to represent increments.
Therefore, users have to count up to 5 short vibrations, and they do not have to estimate the duration of long vibrations.
-We compared this set with sets A, C and E in a second laboratory study.
+We compared this set with sets A, C, and E in a second laboratory study.
Participants identified these patterns with the same or better performance than the patterns of the other sets.
\paragraph{Distance between input and answer}
However, the proportions are larger with set B, which confirms the idea that counting short vibrations is easier than estimating the duration of long vibrations.
Interestingly, with set D the participants' precision was higher on the middle-range values.
-We explain this with the confusion due to the numbers being represented by the duration of the long vibrations at the end of the patterns.
-Since participants reported they counted backwards, this result shows that they sometimes forgot to do so.
-It had a strong influence on the result, which is another reason to reject this patterns set.
+We explain this with confusion due to the numbers being represented by the duration of the long vibrations at the end of the patterns.
+Since participants reported they counted backward, this result shows that they sometimes forgot to do so.
+It had a strong influence on the result, which is another reason to reject this pattern set.
\paragraph{Pre-attentive signals}
-Many participants mentioned that with pattern set C, they liked the long vibrations, which helped them focusing on the upcoming short vibrations and cound them.
+Many participants mentioned that with the pattern set C, they liked the long vibrations, which helped them focus on the upcoming short vibrations and count them.
We believed this aspect would be important in a real context when users receive information while they perform their daily activities.
Therefore we conducted a 28-days longitudinal study.
-Participants were presented random numbers of set F.
-Half-of them received a pre-attentive vibration of $700ms$ between the actual pattern.
-In order to make sure participants do not expect the notifications, they were sent twelve vibrations per day at semi-random times within one-hour window between 7am and 8pm.
+Participants were presented with random numbers of set F.
+Half of them received a pre-attentive vibration of $700ms$ between the actual pattern.
+In order to make sure participants do not expect the notifications, they were sent twelve vibrations per day at semi-random times within a one-hour window between 7am and 8pm.
This schedule helped to cover different activities from the users such as their commute, when they bring their kids to school, their day at work, and some evening activities.
The results did not show a significant difference in terms of answer accurracy rate.
-However, when discussing with participants after the experiment, most of the group who did not have the vibration answered that a pre-vibration would have been useful.
+However, when discussing with participants after the experiment, most of the groups who did not have the vibration answered that a pre-vibration would have been useful.
Almost all of the participants in the group who had it answered that the pre-vibration was useful to them.
-So despite a lack of quantitative improvements, we recommend to provide a pre-attentive vibration because users prefer to have it.
+So despite a lack of quantitative improvements, we recommend providing a pre-attentive vibration because users prefer to have it.
%Can people notice and interpret correctly information when they do not expect the tactile cues?
\subsubsection{Discussion and Conclusion}
-Participants identified the patterns with a high accurracy both in the laboratory (96\%) and in-situ (89\%).
-We note that in the longitudinal study, the patterns were presented in a random order.
-However in an activity monitoring scenario, they would be presented in an increasing order.
+Participants identified the patterns with high accuracy both in the laboratory (96\%) and in-situ (89\%).
+We note that in the longitudinal study, the patterns were presented in random order.
+However, in an activity monitoring scenario, they would be presented in increasing order.
Hence we conjecture that participants could identify them better.
The main limitation of this work is certainly its scalability.
This next contribution is also about the extension of the haptic output vocabulary.
However, contrary to the previous contribution, in this project we studied the output vocabulary for a new kind of tactile technology: programmable friction.
Two different technologies exist for changing the perceived friction of a surface.
-The first one is electrovibration, and uses a high voltage signal on an
+The first one is electrovibration,and uses a high voltage signal on an
electrode to stick the user's finger on the surface~\cite{strong70}.
-Therefore this technology incrreases the perceived friction.
+Therefore this technology increases the perceived friction.
The second technology leverages the squeeze film effect to reduce the perceived friction~\cite{biet07}.
Technically, the whole surface vibrates at a high frequency, typically tens of thousand Hertz~\cite{amberg11}.
This frequency is way beyond the tactile sensitivity range.
Therefore we had to work with research prototypes, called STIMTAC, that were evolving in parallel to our own studies.
Second, we had to characterize the tactile sensations produced with this technology in order to define the output vocabulary.
Our results guided the design of the devices and the improvements of the devices enabled better sensations.
-The co-evolution of both research activities pushed forward this technology, and it is today developped by Hap2U\footnote{\href{https://www.hap2u.net/}{https://www.hap2u.net/}}.
+The co-evolution of both research activities pushed forward this technology, and it is today developed by Hap2U\footnote{\href{https://www.hap2u.net/}{https://www.hap2u.net/}}.
\subsubsection{Technical considerations}
Our colleagues built several prototypes.
-They glued an array of piezo-electric ceramics under the tactile surface.
+They glued an array of piezoelectric ceramics under the tactile surface.
Their objective is to control the actuation of the ceramics to deform the whole surface consistently~\cite{biet07}.
The ceramics are activated by two electrical signals with a phase shift between each other.
The amplitude is maximized with a $180^\circ$ phase shift, and zero with a $0^\circ$ phase shift.
It is however possible to change the amplitude over time.
In particular, the prototypes have sensors to locate the contact points so that we can adjust the tactile feedback depending on the finger position on the tactile surface.
-The typical feedback with this technology consists in steps between two slickness values~\cite{biet08}.
+The typical feedback with this technology consists of steps between two slickness values~\cite{biet08}.
Previous work shows for example that using sticky targets increases target selection performance~\cite{casiez11}.
-Authors showed that the increase of performance is due to the return of information, and not to a physical effect.
+Authors showed that the increase in performance is due to the return of information, and not to a physical effect.
\subsubsection{Perception of programmable friction}
The connection between the command and what users perceive through their fingers is not trivial though.
-This is a typical example of the phenomenon discussed at the beginning of this chapter, and illustrated on \reffig{fig:hapticpath}.
-Both the relation between the command and the vibration amplitude and the relation between the amplitude and the sensation of slickness are not linear~\cite{biet07}.
-They are affected by many environmental factors such as air moisturre, temperature; surface properties such as material, cleanliness; and fingers aspect: tribology, cleanliness, moisture.
+This is a typical example of the phenomenon discussed at the beginning of this chapter and illustrated on \reffig{fig:hapticpath}.
+Both the relation between the command and the vibration amplitude and the relation between the amplitude and the sensation of slickness is not linear~\cite{biet07}.
+They are affected by many environmental factors such as air moisture, temperature; surface properties such as material, cleanliness; and fingers aspect: tribology, cleanliness, moisture.
There are differences in performance between prototypes.
-Some of these differences are due to their hand-made nature, especially the ceramics glueing.
+Some of these differences are due to their hand-made nature, especially the ceramics gluing.
Others are just due to the updates resulting from lessons learned with each prototype.
-The major consequence of this is that the actual values of of psychophysics studies results are tied to a particular prototype.
+The major consequence of this is that the actual values of psychophysics studies results are tied to a particular prototype.
They are hard to generalize.
However, lessons learned are useful for improving the technology and understand its benefits and limitations.
-The first study in which I was involved consisted in evaluating the Just Noticeable difference (JND) of friction between two adjacent zones.
+The first study in which I was involved consisted in evaluating the Just Noticeable Difference (JND) of friction between two adjacent zones.
The objective is to measure the useful resolution of the device.
With this information, our colleagues can optimize the power consumption of the device, and we can design more complex patterns such as textures.
This work was not published, therefore I will get in more details below with a new statistical analysis.
%The left and the right part of the surface was split into two equal sized areas.
%We were interested
-We used an one-up/two-down adaptative method, which enables a faster convergence to the JND value~\cite{leek01}.
-It consists in reducing the intensity of the signal after two good answers, and augmenting it after one wrong answer (\reffig{fig:adaptativeprocedure}).
-The evaluation of each trial used a 3-alternatives forced choice (3-AFC).
-This means participants were presented 3 configurations.
-One of them had a signal: a difference of friction between the left and right side of the device.
+We used a one-up/two-down adaptative method, which enables a faster convergence to the JND value~\cite{leek01}.
+It consists in reducing the intensity of the signal after two good answers and augmenting it after one wrong answer (\reffig{fig:adaptativeprocedure}).
+The evaluation of each trial used a 3-alternatives forced-choice (3-AFC).
+This means we presented participants with 3 configurations.
+One of them had a signal: a difference of friction between the left and right sides of the device.
This difference of friction corresponds to the intensity of the signal.
%A randomly chosen side presented the tested reference level, and the other presented another value that depend on the tested intensity.
The friction was uniform on the whole surface for the two other configurations.
Participants had to tell which configuration presented a signal.
-This procedure reduces the chance level, and avoid anticipation biases.
+This procedure reduces the chance level and avoids anticipation biases.
The position of the signal among the 3 configurations was random, and the side presenting the reference level was random as well.
\begin{figure}[htb]
The first trial of each block used the largest difference for the chosen reference value.
For example, with a reference level of $0^\circ$ the other value was $180^\circ$.
-Then, the value decreased of $1.8dB$ after two good answers in a row, and increased of $1.8dB$ after a wrong answer.
-After 3 reversals we reduced the increment/decrement to $1.2dB$ since participants went closer to the perception threshold.
+Then, the value decreased by $1.8dB$ after two good answers in a row and increased by $1.8dB$ after a wrong answer.
+After three reversals we reduced the increment/decrement to $1.2dB$ since participants went closer to the perception threshold.
The block ended at the \nth{13} reversal.
We estimated the threshold by averaging the values corresponding to the last 10 reversals.
%Participants typically performed between 30 to 50 trials per block.
-We experimented six reference levels, one for each block.
+We experimented with six reference levels, one for each block.
The values were spread out linearly between the minimum and maximum command (\degr{0} to \degr{180} phase shift).
For the first three values (\degr{0}, \degr{36}, and \degr{72}) we searched the minimum greater value for which participant could feel a step.
For the last three values (\degr{108}, \degr{144}, and \degr{180}) we searched the minimum lower value for which participant could feel a step.
\end{figure}
We instructed participants to use the index finger of their dominant hand only.
-They wore a noise canceling headset to avoid guesses with audio cues.
+They wore a noise-canceling headset to avoid guesses with audio cues.
We cleaned the surface with isopropyl alcohol before each block.
To make sure participants felt the signal in both directions, we instructed them to perform at least 3 back-and-forths between the left and right zones of the surface.
%Before each trial, the device measured the amplitude of vibration and adjusted the signal to ensure a consistent effect over each trial.
The experiment application showed a pressure bar and participants were instructed to remain in a specified range.
-The experiment started with a training phase in which signals of different intensity were presented to participants.
-We presented them a low-intensity signal to make sure they will be able to perform all 6 blocks.
+The experiment started with a training phase in which signals of different intensities were presented to participants.
+We presented them with a low-intensity signal to make sure they will be able to perform all 6 blocks.
All the participants felt this signal.
The application showed three visually identical items representing the three configurations of the trial.
Participants could switch between them with the \Space key but could not go back to the previous ones.
After exploring the three items, participants had to indicate which one presented the signal with the \keys{1} \keys{2} \keys{3} keys.
Participants did not receive any feedback regarding whether their answer was good or wrong.
-12 participants took part of this experiment, all of them were right-handed, their mean age was $27.7$ years old, and none of them had a known tactile sensitivity issue.
+12 participants took part in this experiment, all of them were right-handed, their mean age was $27.7$ years old, and none of them had a known tactile sensitivity issue.
Participants performed 2 sessions of 6 blocks with pauses between blocks and the two sessions happened on a different day.
-Each block typically consisted in 30 to 50 trials and lasted about 20 minutes.
+Each block typically consisted of 30 to 50 trials and lasted about 20 minutes.
The order of blocks was balanced with a Latin square.
\paragraph{Results and discussion}
In this analysis, we used 10 \textsc{Reversals} $\times$ 6 \textsc{Levels} $\times$ 12 \textsc{Levels} = 720 trials.
\reftab{tab:jndstimtac} shows the mean JND value and standard deviation for each reference level.
\reffig{fig:stimtacmarches} shows two representations of the results.
-On the left, for each level the bars represent JND value.
+On the left, for each level, the bars represent the JND value.
%On the right, for each level the bars represent the absolute values of both the reference level and the JND.
-On the right, for each level the bottom of the bars represent the reference level and the height of the bar is the JND value.
-It gives an absolute view of the phase-shift associated with the reference level and the JND.
+On the right, for each level, the bottom of the bars represents the reference level and the height of the bar is the JND value.
+It gives an absolute view of the phase shift associated with the reference level and the JND.
For both charts, the error bars are 95\% confidence intervals.
-On the right side the error bar is on the variable end because the reference level did not change.
+On the right side, the error bar is on the variable end because the reference level did not change.
\begin{figure}[htb]
\centering
Unfortunately, at the time I am writing this I have no access to the amplitude measurement data.
This makes it impossible to draw more general recommendations.
The measurement with a laser vibrometer of a \degr{180} command gives a $2.2\mu m$ amplitude of vibration.
-It is however difficult to measure an actual friction value because it depends on the force applied on the surface, which varies when users move their finger to explore the surface.
+It is however difficult to measure an actual friction value because it depends on the force applied on the surface, which varies when users move their fingers to explore the surface.
\subsubsection{Output vocabulary: Tactile Textures}
-The exploration of low level parameters such as the difference of friction between two adjacent zones as discussed in the previous section, enables the design of highel level tactile parameters such as textures.
-There is a vast literature on the perception of tactile textures.
+The exploration of low-level parameters such as the difference of friction between two adjacent zones as discussed in the previous section enables the design of higher-level tactile parameters such as textures.
+The literature on the perception of tactile textures is vast.
It is an active research topic in psychology for decades.
-However we struggled finding an exact definition of a tactile texture.
+However, we struggled to find an exact definition of a tactile texture.
Many studies like~\cite{lederman82,lederman72,yoshioka01} focus on roughness.
Roughness can be seen as a fine-grain texture for which users do not feel individual elements.
There is research in the physical world, with studies on fabrics~\cite{parriaux19,picard03}.
In the digital world, there is a notion of patterns~\cite{gescheider05}, that are sometimes direct translations of visual textures~\cite{ikei97}.
-Schellingerhout studied repeated patterns, and describes 3 configurations~\cite{schellingerhout98}.
+Schellingerhout studied repeated patterns and describes 3 configurations~\cite{schellingerhout98}.
The first one is \emph{smooth textures}, which corresponds to a uniform signal without repetition.
The second one is a \emph{homogeneous texture}, which is a repeated pattern without variations.
The last one is a \emph{gradient texture}, which is a repeated pattern of different scales.
Like every other pattern type, we can adjust the friction level.
%It corresponds to the smooth configuration in Schellingerhout's classification.
The second pattern is a \emph{step}.
-It corresponds to a frontier between two adjacent zones which have a different friction.
-It is the smallest building block we will use later for designing more complext patterns and textures.
+It corresponds to a frontier between two adjacent zones which have a different friction value.
+It is the smallest building block we will use later for designing more complex patterns and textures.
We can adjust its position and direction.
The third pattern is a \emph{shape}: a localized pattern distinct from the background.
It has two steps so that the user can move through it.
-Its parameters arre position and size (width).
+Its parameters are position and size (width).
The fourth pattern is a \emph{field}, a regular repetition of a shape.
-With a sufficiently low size and high number of repetition, users are not able to count the item while exploring the surface.
+With a sufficiently low size and a high number of repetitions, users are not able to count the item while exploring the surface.
They rather have a sensation of roughness\fixme{REF?}.
-One of the parameters is the duty-cycle, which is the ratio between the signal size and the period size.
+One of the parameters is the duty cycle, which is the ratio between the signal size and the period size.
We can also adjust the number of repetitions and the width, which together controls the density of the pattern.
The fifth pattern is a \emph{gradient}, repetition of a shape, with a variable size.
There are many ways to increase or decrease the size of shapes of a gradient: linearly, exponentially, etc.
Finally, the sixth pattern is a \emph{random} series of shapes.
-We can control the minimum and maximum size of shapes.
+We can control the minimum and maximum sizes of shapes.
\begin{figure}[htb]
\definecolor{cellblue}{rgb} {0.17,0.60,0.99}
We define a \defword{Tactile texture} as combination of one of several patterns on several dimensions or at different scales.
\end{definition}
-Textures can have patterns of different scales, providing different levels of details.
-For example physical objects can have a rugosity due to the microstructure of their material and a higher grain structure due to carving of their surface.
+Textures can have patterns of different scales, providing different levels of detail.
+For example, physical objects can have a rugosity due to the microstructure of their material and a higher grain structure due to the carving of their surface.
\reffig{fig:tactiletexture} shows two examples of tactile textures.
-The first one is a sequence of tactile patterns of different types: field, constant, gradient and random.
+The first one is a sequence of tactile patterns of different types: field, constant, gradient, and random.
Users can most likely identify different parts in the textures, without necessarily locate their boundaries.
The second one repeats a field-type pattern, which is itself a repetition of a shape.
-We can also see it as a frequency modulation of two signals.
+We can also see it as frequency modulation of two signals.
We can obviously use the same structure and parameters than with vibrotactile Tactons (see \reffig{fig:lexical} and \ref{fig:syntactic}).
-However the range of friction we can produce with this device is not as wide as the range of vibration amplitudes we can produce with state-of-the-art vibrotactile actuators.
+However, the range of friction we can produce with this device is not as wide as the range of vibration amplitudes we can produce with state-of-the-art vibrotactile actuators.
Therefore we cannot simply translate vibrotactile Tactons into tactile textures so far.
It would be interesting to perform JND studies with another device that produces a higher quality variable friction feedback, such as devices made by Hap2U\footnote{\href{https://www.hap2u.net/}{https://www.hap2u.net/}}.
Other technologies are indeed required for three spatial dimensions, like ultrasound actuators~\cite{carter13}.
%The pattern types presented in \reffig{fig:tactilepattern} is not necessarily cover all possible patterns.
%There are for instance many ways to increase the size of shapes of a gradient: linearly, exponentially, etc.
-The examples of tactile patterns and textures we presented do not necessarily cover all possiblilities.
+The examples of tactile patterns and textures we presented do not necessarily cover all possibilities.
However, it is an illustration of the expressive power of tactile textures made of elementary steps.
We will next discuss an evaluation of users' perception of tactile patterns.
\paragraph{Evaluation of tactile patterns}
%The evaluation of tactile patterns is complex because the design space is large.
-The first interesting research question is whether users are able to distinguish the patterns.
+The first interesting research question is whether users can distinguish the patterns.
The way of evaluating this is not trivial though because the design space is large and it is difficult, not to say impossible, to present all of them with sufficient repetitions for an accurate analysis.
Therefore we must evaluate a subset of all possible patterns
Recent work addressed this issue with a new method for sampling the design space~\cite{demers21}.
-At the time, we multidimensional scaling (MDS) because of the multidimensional nature our patterns.
-This method consists in asking participants to group items together and use the number of times they are grouped together as a similarity metric.
+At the time, we used multidimensional scaling (MDS) because of the multidimensional nature of our patterns.
+This method consists in asking participants to group items and use the number of times they are in the same group as a similarity metric.
Then we compute the number of required dimensions and map each item to a position in space so that the distance between two items is proportional to their dissimilarity.
-Finally we identify clusters of similar patterns.
-This method was already succeessfully used to evaluate Tactons~\cite{enriquez06}.
+Finally, we identify clusters of similar patterns.
+This method was already successfully used to evaluate Tactons~\cite{enriquez06}.
\reffig{fig:stimtacpatterns} shows the patterns we evaluated~\cite{potier16}.
They are made of 5 \textsc{shapes} and 7 \textsc{densities}, for a total of 34 patterns (the lowest density vertical line and squares are identical).
The secondary research question is whether the perception of tactile textures with a variable friction device is similar to the perception of a similar pattern on a physical surface.
We can expect differences because this technology cannot produce edges that we can feel under the fingertip.
With a squeeze film effect device, edges are produced by changing the friction of the whole surface depending on the finger position.
-Therefore in our experiment we compared tactile patterns rendered on a Stimtac device, and 250g dull coated paper cards as tangible surfaces.
-The stimulation on the paper is created with a transparent ink, which feels stickier than the paper.
-The stickiness depends on the number of printed layers, printed with a HP Indigo Digital Press® printer.
+Therefore in our experiment, we compared tactile patterns rendered on a Stimtac device, and 250g dull coated paper cards as tangible surfaces.
+The stimulation on the paper is created with transparent ink, which feels stickier than the paper.
+The stickiness depends on the number of printed layers, printed with an HP Indigo Digital Press® printer.
We performed a pilot study with 3 users to define the number of layers required to match the stimulation with the STIMTAC.
We opted for 30 layers, which makes a 0.05 mm thickness.
Both STIMTAC and cards have the same size: 8cm wide and 4cm high.
Interested readers will find more details on the experimental details and the full analysis in the corresponding paper~\cite{potier16}.
Here I will focus on the main findings.
We designed the patterns with several shapes and densities.
-Therefore we expect partitipants to group patterns of same shapes or densities.
-However the MDS analysis fails at identifying a good sets of clusters with 2 or 3 dimensions.
+Therefore we expect participants to group patterns of the same shapes or densities.
+However, the MDS analysis fails at identifying a good set of clusters with 2 or 3 dimensions.
This means that this is unlikely there is a consensual grouping strategy among users and conditions.
We observed participants often grouped vertical and horizontal lines per shape in both conditions.
We hypothesize this is due to the fact that the sensation with these two shapes is different whether you explore them horizontally or vertically.
Next, we analyzed the composition of pattern groups made by participants.
We observed if groups contained the same \textsc{shape}, same \textsc{density} or if users \textsc{mixed} shapes and densities.
In the paper condition, participants used more often a \textsc{shape} or \textsc{density} strategy than a \textsc{mixed} strategy.
-In particular when they made groups of 6 or 7 items, they dominantly used a \textsc{shape} strategy.
+In particular, when they made groups of 6 or 7 items, they dominantly used a \textsc{shape} strategy.
Interestingly, in the Stimtac condition participants mostly used a \textsc{mixed} strategy, and made more groups of 2 items.
Because the grouping strategy was different in the two conditions, we assume that they perceived the patterns differently with the paper cards and Stimtac.
This project is a typically interdisciplinary project in which research was made on two fronts at the same time.
On one side, our Electrical engineering colleagues designed, simulated, and implemented the device itself.
On our side, we evaluated the perception of the haptic effect by users.
-Both research benefitted to the other.
+Both research activities benefitted from the other.
Our main contribution was the evaluation of variable friction parameters for the design of
an output vocabulary with programmable friction devices.
-We first worked on the lexical level, and evaluated the JND of steps for six reference values of friction.
+We first worked on the lexical level and evaluated the JND of steps for six reference values of friction.
We observed differences of perception between reference values.
-We attributed these differences to both the non-linearity of the mechanical effect resulting from the command, and the perception of the mechanical effect.
-As a result, the commands were adapted on the device.
+We attributed these differences to both the non-linearity of the mechanical effect resulting from the command and the perception of the mechanical effect.
+As a result, the commands were adapted to the device.
-Then we worked on the syntactic level, and proposed definitions of tactile patterns and textures.
+Then we worked on the syntactic level and proposed definitions of tactile patterns and textures.
We compared the users' estimation of similarity of tactile patterns made of different shapes and densities implemented with a Stimtac device and with coated paper cards.
-We observed differences of grouping strategy across conditions, suggesting differences of perception between the haptic device and the paper cards.
-It means that results about perception made with research prototypes are hard to generalize,and that using physical props is an alternative to evaluate best-case scenarios.
+We observed differences in grouping strategy across conditions, suggesting differences of perception between the haptic device and the paper cards.
+It means that results about perception made with research prototypes are hard to generalize and that using physical props is an alternative to evaluate best-case scenarios.
%\cite{bertin83}
The manufacturing process of touch interfaces such as dashboards augmented with haptic feedback is complex.
Mechanical actuators must be attached underneath such that the vibration transmits to the interactive places of the surfaces.
-In this project, we investigate a new kind of actuators.
+In this project, we investigate a new kind of actuator.
%However, the originality of this work is that we used a new type of vibrotactile actuator.
-They are printed on a flexible substrate with a piezo electric ink.
+They are printed on a flexible substrate with a piezoelectric ink.
Therefore, these actuators can be embedded in plastic injection molds when dashboard parts are produced.
They can even be integrated into curved interactive surfaces.
%This is convenient for dashboards with tactile input.
\subsubsection{Experimental platform}
\label{sec:printgetsplatform}
-The design of the actuators is a trade-off between their size and thickess, the number of layers, and the signal voltage.
-Our colleagues whom designed and implemented these actuators performed FEM simulations and measured the response to signal with laser vibrometers~\cite{poncet17,poncet16}.
+The design of the actuators is a trade-off between their size and thickness, the number of layers, and the signal voltage.
+Our colleagues who designed and implemented these actuators performed FEM simulations and measured the response to signal with laser vibrometers~\cite{poncet17,poncet16}.
They gave us several prototypes that we could use to design vibrotactile widgets.
The first prototype (top of~\reffig{fig:printedslider}) had six buttons embedded in a molded plastic dashboard part.
The clamping area was a circle around each actuator.
The second prototype was a bare flexible substrate with seven actuators.
We designed a clamping frame around the actuators so that the vibration could propagate on the whole length of the slider.
We added tension strings to tighten the frame so that the clamping area could resonate.
-This is the same approach than a drum head on a drum shell.
+This is the same approach as a drum head on a drum shell.
The capacitive touch sensor, printed with silver ink, is under the actuators.
The setup is depicted at the bottom of~\reffig{fig:printedslider}.
\end{figure}
We built a custom PCB with piezo drivers\footnote{\href{http://www.ti.com/product/DRV2667.}{TI DRV2667}} (one per actuator), and the capacitive sensing chip~\footnote{\href{http://www.microchip.com/wwwproducts/en/CAP1188}{Microchip CAP1188} for buttons and \href{http://www.microchip.com/wwwproducts/en/CAP1214}{Microchip CAP1214} for sliders}.
-The chips communicate with the main board that runs the application\footnote{\href{https://www.raspberrypi.org/products/raspberry-pi-3-model-b/}{Raspberry Pi 3B}} through an I2C bus.
-The drivers have two mode of operation. Either we play pre-recorded signals, or we provide an audio signal in the tactile frequency-range.
+The chips communicate with the mainboard that runs the application\footnote{\href{https://www.raspberrypi.org/products/raspberry-pi-3-model-b/}{Raspberry Pi 3B}} through an I2C bus.
+The drivers have two modes of operation. Either we play pre-recorded signals, or we provide an audio signal in the tactile frequency range.
The pre-recorded signal solution is easier because it does not require additional hardware.
-The audio solution requires a sound generation hardware (typically a sound card with one channel per driver), but the signal generation is more flexible.
+The audio solution requires sound generation hardware (typically a sound card with one channel per driver), but the signal generation is more flexible.
We chose to use the audio mode for designing iteratively the tactile signals.
We generated the audio signals with Purr-Data~\cite{bukvic16}.
Then when used the other mode when the tactile signals were validated.
\subsubsection{Vibrotactile widgets}
-The idea of using vibrations to simulate button clicks on touch surfaces started with vibrotactile actuators attached to PDAs~\cite{fukumoto01,nashel03,poupyrev02}, then mobile phones~\cite{brewster07,hoggan08}.
-This was before phone manufacturers included vibrotactile actuators to mobile phone.
-And even now that mobile phones do have one, it is low quality (ERM or LRA) and mostly used for message or call notifications.
+The idea of using vibrations to simulate button clicks on touch surfaces started with vibrotactile actuators attached to PDAs~\cite{fukumoto01,nashel03,poupyrev02}, then mobile phones~\cite{brewster07,hoggan08}.
+This was before phone manufacturers included vibrotactile actuators in mobile phones.
+And even now that mobile phones do have one, it is low quality (ERM or LRA) and mostly used for messages or call notifications.
They sometimes propose vibrations for button presses, but the quality of this feedback is poor.
Indeed other actuators provide sharper vibrotactile feedback.
We discussed this at the beginning of this chapter.
-Voice coil actuators provide precise and strong vibrations~\cite{yao10}, and piezo actuators have a smaller form factor, and are convenient for implementing buttons~\cite{tashiro09,lylykangas11}.
+Voice coil actuators provide precise and strong vibrations~\cite{yao10}, and piezo actuators have a smaller form factor and are convenient for implementing buttons~\cite{tashiro09,lylykangas11}.
Our challenge is that printed actuators are thin (between $4\mu m$ and $10\mu m$).
-Therefore the vibration propagation requires a careful design as discussed in the previous page.
+Therefore the vibration propagation requires a careful design.
+% as discussed on the previous page.
%Designing better tactile buttons requires knowing how people operate buttons, and what they perceive.
%Neuromechanics button press ~\cite{oulasvirta18}
-Kim and Lee analyzed force-displacement curves of physical buttons and designed high quality vibrotactile feedback that emulates button presses~\cite{kim13}.
+Kim and Lee analyzed force-displacement curves of physical buttons and designed high-quality vibrotactile feedback that emulates button presses~\cite{kim13}.
They split force-displacement curves into two types of sections: slopes and jumps, which are delimited by tactile points (\reffig{fig:buttonfeedback}).
-Slopes are spring-like sensations that correspond to the material resistance.
-When pressing a button we feel a first resistance before the click, then another one when the button reaches its end.
-When releasing a button we feel another resistance before the click sensation.
+Slopes are spring-like sensations that correspond to material resistance.
+When pressing a button, we feel first the resistance before the click, then another one when the button reaches its end.
+When releasing a button, we feel another resistance before the click sensation.
The tactile points (1) and (3) represent the click sensations when the button physically switches, and the bottom-out (2) represents the end of the button.
We adapted and simplified these curves for the design and implementation of our buttons.
We describe further our implementation of buttons, sliders, and touchpads in~\cite{frisson20,frisson17}.
% \node[x=\scale,y=\scale, align=right, text width=1.8cm, anchor=east] () at (0,20){circles};
\end{tikzpicture}
\tikzexternaldisable
- \caption[.]{Force-displacement curve for a tactile button, adapted and simplified from~\cite{kim13}.}
+ \caption[Force-displacement curve for a tactile button.]{Force-displacement curve for a tactile button, adapted and simplified from~\cite{kim13}.}
\label{fig:buttonfeedback}
\end{figure}
A difficulty of this work was the long manufacturing process of actuators.
It required weeks of planning, and the actuators were printed in a clean white room.
-This long process limited the number of iterations we could perform for designing the actuator layout and properties such as thickness, shapes ,and sizes.
+This long process limited the number of iterations we could perform for designing the actuator layout and properties such as thickness, shapes, and sizes.
Therefore at each iteration, we printed several configurations then tested them to select the most appropriate one.
However, it limited the type of user studies we could perform.
One of the major differences between this vibrotactile technology and other piezo-based actuators is that their thickness is very low.
-It is an advantage because it uses fewer materials.
+It is an advantage because it uses less materials.
It is also a drawback because the amplitude of vibration is much lower.
Therefore the vibration hardly transmits to thick surfaces like a 1mm thick plastic dashboard.
The alternative is placing the actuators on holes that define a clamping area so that the substrate resonates like a drum shell.
This solution brings an interesting property that other technologies do not have.
-The vibration is localized to the clamping area therefore it is localized.
+The vibration is localized to the clamping area, therefore it is localized.
Hence with a dashboard with several buttons and sliders, it is possible to vibrate buttons individually.
This project is the exact opposite.
We embrace physical controls and their haptic properties, and we study how we can use them differently.
%better include them in our daily activities beyond the way they usually work.
-In this work we focused on desktop interaction with the augmentation of desktop peripherals.
-% peripherals: keyboards, mice and screens.
+In this work, we focused on desktop interaction with the augmentation of desktop peripherals.
+% peripherals: keyboards, mice, and screens.
There are many examples of extensions of desktop peripherals in past research, in particular keyboards.
-For example additional sensors enable contact sensing on the keys of a keyboard~\cite{rekimoto03}, gesture on the whole keyboard surface~\cite{block10,kato10,taylor14,zhang14}, or force sensing on keys~\cite{dietz09}.
-In other works, actuators are embedded in each key to make them harder to press~\cite{hoffmann09,savioz11}.
-Mice werre also augmented, with shape-changing features to enable notifications or provide an elastic input device for continuous rate control~\cite{kim08}.
-More generally, the idea of changing the shape of a physical controler is to provide different affordances~\cite{michelitsch04,kim16}.
+For example, additional sensors enable contact sensing on the keys of a keyboard~\cite{rekimoto03}, gesture on the whole keyboard surface~\cite{block10,kato10,taylor14,zhang14}, or force sensing on keys~\cite{dietz09}.
+In other works, actuators are embedded in each key to make them harder to press~\cite{hoffmann09,savioz11}.
+Mice were also augmented, with shape-changing features to enable notifications or provide an elastic input device for continuous rate control~\cite{kim08}.
+More generally, the idea of changing the shape of a physical controller is to provide different affordances~\cite{michelitsch04,kim16}.
The work we have done with Métamorphe explores the augmentation of keyboards for increasing its input vocabulary~\cite{bailly13}.
We embedded solenoids in keys such that they can either be raised or lowered.
-In both positions they could be pressed though.
+However, they could be pressed in both positions.
Not only it changes the geometry of the keyboard, but it also gives users access to the sides of the keys.
We will discuss the augmentation of desktop interaction at the device level in the next section.
%Further, Gervais \etal turned every object in the environment into a screen, to enrich our interaction with interactive systems~\cite{gervais16}.
Actuation is another modality that augments desktop interaction.
For example, a fleet of small robots can represent data dynamically~\cite{legoc16}.
-However the combination of ubiquitous displays with actuation brings another dimention that increases the interaction vocabulary~\cite{roudaut13a}
-Our approach with Living Desktop also considers the desktop workstation as a whole that should be integrated in its environment~\cite{bailly16}.
+However, the combination of ubiquitous displays with actuation brings another dimension that increases the interaction vocabulary~\cite{roudaut13a}
+Our approach with Living Desktop also considers the desktop workstation as a whole that should be integrated into its environment~\cite{bailly16}.
However, our primary focus is on augmenting devices and their interaction by leveraging their physical properties.
These two research projects are complementary, and they focus on different levels.
Métamorphe focuses on the device level while Living Desktop focuses on the desktop level.
-In both cases we use actuation as a mechanish to provide new features, with two paradigms in mind.
+In both cases, we use actuation as a mechanism to provide new features, with two paradigms in mind.
The first one is shape-changing interaction: the shape of an object is a signifier of its affordances.
Hence changing the shape of a device is an interesting way of providing and advertising an extended interactive vocabulary.
The second paradigm is tangible interaction, which “augments the real physical world by coupling digital information to everyday physical objects and environments.”\cite{ishii97}.
Pointing devices rely on movement measurements.
Keyboards use binary key positions as input data.
In the Métamorphe project~\cite{bailly13}, we actuated the keys so that they can either be up or down (\reffig{metamorphe}, left).
-However, contrary to other augmented keyboards~\cite{hoffmann09,savioz11}, userrs can prress its keys, whether the key is up or down.
+However, contrary to other augmented keyboards~\cite{hoffmann09,savioz11}, users can press its keys, whether the key is up or down.
\begin{figure}[!htb]
\centering
This shape-changing keyboard provides new interactive properties compared to regular keyboards.
First of all, it changes the haptic properties of the keyboard.
-When the users' hand scan the keyboard, they can distinguish raised keys.
+When users scan the keyboard with their hands, they can distinguish raised keys.
Not only it helps users to locate raised keys, but also the surrounding keys because the raised keys provide a reference point.
-This is the same phenomenon than the little notches on the \keys{F} and \keys{J} keys that help touch typists placing their hand on the keyboard, at a differrent scale and with more flexibility.
+This is the same phenomenon as the little notches on the \keys{F} and \keys{J} keys that help touch typists placing their hand on the keyboard, at a different scale, and with more flexibility.
We experimented this phenomenon with a user study~\cite{bailly13}.
It is indeed an interesting property for eyes-free interaction.
We can imagine for example that keys corresponding to a keyboard shortcut are raised when the \ctrl key is pressed.
When a key is up, users can push it in four directions, pinch it (\reffig{metamorphe}, right), or even rotate it.
With a force sensor all around it, we can turn the key into an isometric pointing device such as a trackpoint.
Previous work showed examples of interactions we can perform with an array of actuated rods~\cite{iwata01,leithinger10,follmer13}.
-Our prototype only actuated eight keys for technical reasons, and we kept the layout of traditional keyboards because our intention was to augment traditional keyboards.
-However, if we put technical limitations aside, we can envision a combination of these two concepts: a shape changing surface, and a new input vocabulary brought by controlers that pop out of the surface.
+Our prototype only actuated eight keys for technical reasons, and we kept the layout of traditional keyboards because we intended to augment traditional keyboards.
+However, if we put technical limitations aside, we can envision a combination of these two concepts: a shape-changing surface, and a new input vocabulary brought by controllers that pop out of the surface.
\subsubsection{Desktop level}
%They are essentially isolated devices, not a set of coherent devices which share the same behavior.
In this project, we observed people when they use a desktop computer.
We identified situations in which they move the peripherals but not for interacting with the computer.
-For example we observed people turning their screen to avoid sun reflexions.
+For example, we observed people turning their screens to avoid sun reflections.
Other users turned their screen either to show visual content to somebody.
%, or to show something in the room in a video conference with the camera affixed to the screen.
-%It is also frequent to move the mouse and keyboard to make space on the desk for something else, or share them with other users to give them the control of the computer.
-It is also frequent to give other people the mouse or keyboard to give them the control over the computer.
+%It is also frequent to move the mouse and keyboard to make space on the desk for something else or share them with other users to give them control of the computer.
+It is also frequent to give other people the mouse or keyboard to give them control over the computer.
In the Living Desktop project, we actuated a mouse, a keyboard, and a screen (\reffig{livingdesktop}).
The mouse and the keyboard can translate in the $x,y$ plane directions.
The keyboard can also rotate.
-The screen can rotate, and translate in the $x$ axis direction.
+The screen can rotate and translate in the $x$ axis direction.
The details of the apparatus are described in~\cite{bailly16}.
\begin{figure}[!htb]
%\paragraph{Telekinesis}
\paragraph{Full control}
-When users have a full control over the actuated devices, they can move them around physically or remotely.
+When users have full control over the actuated devices, they can move them around physically or remotely.
%\paragraph{Video Conference}
For example, when video-conferencing with a desktop computer, the camera is usually affixed to the screen.
We can manipulate it with full control to adjust the field of view.
The problem is when remote users would like to show an object they manipulate outside the camera field of view.
They have to move the screen at the same time that they are manipulating the object.
-In this scenario, we take the contrrol over the remote screen to adjust the field of view and make sure we can see what the remote users would like to show.
+In this scenario, we take the control over the remote screen to adjust the field of view and make sure we can see what the remote users would like to show.
%In this scenario the screen follows the user so that he can always see the video conference, and show what he is doing to his collaborators.
%The user does not control the screen position in the strict sense of the term. However he can activate or deactivate this behavior and still control the screen position manually or with another interface.
%the user defines the constraints of the devices movements.
We sometimes need to watch information on our screen while moving in a room, like when working on a whiteboard.
We implemented a scenario in which the monitor orientation follows users in their office
-It displays notifications such as for new emails, agenda alerts, missed calls, etc.
+It displays notifications such as new emails, agenda alerts, missed calls, etc.
It also uses proxemic interaction~\cite{roussel04} by adapting the text size so that it is readable regardless of the distance.
%Tidying. To keep the desk tidy, the devices move away when the user shuts down the computer, when he leaves his office or after a period of inactivity (e.g. 10mn). Moreover, the devices can move to their charging stations. This is especially useful with state of the art wireless devices (e.g. keyboard with embedded screens [4] or actuators [2], shape-changing mouses [21]) using more energy than conventional devices.
\subsubsection{Discussion and conclusion}
This work on actuated devices is indeed different from projects discussed in the previous sections.
-The previous projects followed the typical view on haptic, that we commonly designate as “haptic feedback”.
-In these prrevious projects we encoded information or rendered haptic properties of objects with forces and vibrations.
-Here we take a step back, and consider the haptic properties of physical objects.
+The previous projects followed the typical view on haptic, which we commonly designate as “haptic feedback”.
+In these previous projects, we encoded information or rendered haptic properties of objects with forces and vibrations.
+Here we take a step back and consider the haptic properties of physical objects.
The properties are due to the objects' shape, size, weight, material, position, etc.
By actuating objects, desktop peripherals in our case, we modified some of these properties, typically the shape and position.
-Our focus here was not on how users perceive these haptic properties, but how we can leverage them to propose new interaction properties.
+Our focus here was not on how users perceive these haptic properties but how we can leverage them to propose new interaction properties.
These projects introduce two concepts that we will develop in \refchap{chap:input} and \refchap{chap:loop}.
-The first one is the idea that haptics does not only cover the sense of touch, but also our ability to manipulate.
+The first one is the idea that haptics does not only cover the sense of touch but also our ability to manipulate.
In our examples, the haptic properties of objects enabled different kinds of manipulation.
-The situation is reversed, and we can see the user as a haptic device that produces forces on a manipualted entity.
+The situation is reversed, and we can see the user as a haptic device that produces forces on a manipulated entity.
The second concept is the idea that we cannot separate haptic as output and haptic as input.
These are two sides of the same coin that forms interaction.
This concept has many consequences, such as the continuum between control and automation, and it is linked to several fundamental paradigms of the literature that we will discuss in \refchap{chap:loop}.
\section{Conclusion}
The work that was presented in this chapter illustrates the systematic approach in my research.
-The objective is not to focus on a particular technology, a parrticular problem or a particular context.
-Rather, I search for an appropriate technology for a given problem in a given context.
-The type of research questions I address is large, and depends in particular on the expertise of my collaborators and the objectives of the research project.
+The objective is not to focus on a particular technology, a particular problem, or a particular context.
+Rather, I search for appropriate technologies for a given problem in a given context.
+The type of research questions I address is large and depends in particular on the expertise of my collaborators and the objectives of the research project.
For example in the \emph{Activibe} project, I collaborated with other researchers in HCI who were interested in using haptic cues for promoting behavior change.
-The focus was not on designing a new device or even a new haptic technology, but to design a way to encode information with an off-the-shelf device.
-Hence, we worked on the design, implmentation and evaluation of tactons.
+The focus was not on designing a new device or even new haptic technologies, but to design a way to encode information with an off-the-shelf device.
+Hence, we worked on the design, implementation, and evaluation of tactons.
The approach was different with \emph{tactile textures} and \emph{printgets}.
-In these case I collaborated with researchers with a background in engineering who were designing a new haptic technology.
+In these cases, I collaborated with researchers with a background in engineering who designed a new kind of haptic technology.
The two situations were different though.
-In the first case I also worked with a postdoc who had a background in cognitive sciences.
+In the first case, I also worked with a postdoc who had a background in cognitive sciences.
Therefore our studies focused on the perception and interpretation of tactile textures.
-In the second case I worked with a postdoc who had a background in audio and music technologies.
+In the second case, I worked with a postdoc who had a background in audio and music technologies.
As a consequence, our work was directed to the signal generation and authoring, and the technical apparatus.
-Finally, with the \emph{actuated devices} project I mainly worked with HCI colleagues, and a master intern with an electrical engineering background.
-The intern designed and implemented most of the robotics part of Living Desktop, I worked mostly on the hardware part of Métamorphe, the software part of both and the observation study, and all of us worked on user studies and the application scenarios.
+Finally, with the \emph{actuated devices} project I mainly worked with HCI colleagues and a master intern with an electrical engineering background.
+The intern designed and implemented most of the robotics part of Living Desktop.
+I worked mostly on the hardware part of Métamorphe, the software part of both, and the observation study
+All of us worked on user studies and the application scenarios.
The complementarity of expertise in my research project is an important aspect that not only guides my own contribution, but also the whole direction of the project.
-These research project have a few limitations.
-Acknowledging them is not only umportant regarding to these projects, but this is also useful hindsights for the evolution of my research practices on the same type of projects.
+These research projects have a few limitations.
+Acknowledging them is not only important regarding these projects, but this is also useful hindsight for the evolution of my research practices on the same type of projects.
While the longitudinal study we performed with \emph{Activibe} is rare and insightful on this kind of topic, there is room for improvement on the tacton design methodology.
-The design rationale was not systematic, so even if we found a satisfactory solution there is probably many other possible designs.
-The difficulty is that the design space is huge, and there are many point of views.
-The main consequence on the results is the difficulty to generalize these results to bigger sets.
+The design rationale was not systematic, so even if we found a satisfactory solution there are probably many other possible designs.
+The difficulty is that the design space is huge, and there are many points of view.
+The main consequence of the results is the difficulty to generalize these results to bigger sets.
The design of large tactons sets is hard in general.
The works of \emph{tactile textures} and \emph{printgets} were interesting examples of projects in which the research on the technology and the research on the usage of the technology feed each other.
They are illustrations of Huot's \emph{designeering} concept~\cite{huot13}.
One of the limitations is that research prototypes are built upon simulations.
-However, real world conditions can have a huge impact on the device performance, and the user's perception.
-This is why an iterative process is efficient at taking ito account both the technological and interaction concerns.
-However the other limitation is the slow iteration process due do the long manufactoring of prototypes.
+However, real-world conditions can have a huge impact on the device performance, and the user's perception.
+This is why an iterative process is efficient at taking into account both the technological and interaction concerns.
+However, the other limitation is the slow iteration process due to the long manufacturing of prototypes.
HCI uses low-fidelity prototypes to bootstrap the first cycles of iterative design.
It is important in such projects to identify alternative technologies that can be used for prototyping.
This way, as HCI researchers, we can give our engineering colleagues specifications at the early stage of the project rather than waiting for their early prototypes that already commit to choices that cannot be changed.
In the \emph{actuated devices} project, we built working prototypes that enabled us to explore the scenarios in real contexts.
The Métamorphe was robust enough to evaluate interactive properties, such as the users' ability to locate raised keys.
-However technical limitations prevented us from actuating all keys, or add all the sensors we would need to explore some of the new input we imagined, typically rotating the keys.
-The Living Desktop was functional, but with technical limitations on speed or forces.
-Therefore a user evaluation with the prototype could have been biased due to these technical limitation.
+However, technical limitations prevented us from actuating all keys, or add all the sensors we would need to explore some of the new input we imagined, typically rotating the keys.
+The Living Desktop was functional but with technical limitations on speed or forces.
+Therefore a user evaluation with the prototype could have been biased due to these technical limitations.
This is why we evaluated the scenarios with videos.
We would certainly have collected more valuable data with more robust prototypes.
projects / hdr.git / commitdiff