The frequency signal typically ranges between \qtyrange{1}{1000}{\hertz}.
The amplitude is controlled with the duty cycle of a high-frequency signal.
We used voice coil actuators, therefore they behave like low-pass filters, which stabilizes this high-frequency signal, hence reducing the amplitude of the actuator's movement.
-Our prototypes used \si{16}{\mega\hertz} controllers with 8 bits timers, which gives a \si{62.5}{\kilo\hertz} loop with 256 levels of amplitude.
+Our prototypes used \SI{16}{\mega\hertz} controllers with 8 bits timers, which gives a \SI{62.5}{\kilo\hertz} loop with 256 levels of amplitude.
It communicated with a host computer with a serial protocol over bluetooth.
\input{figures/actuatorcircuit.tex}
\input{figures/dwellpointing.tex}
The cursor has no color and gives no tactile feedback when it is not over a target.
-When it hovers a target, it is colored and all the four actuators vibrate at \si{50}{\hertz}.
-After \si{1}{\ms} over the button, a ring is drawn around the cursor, and all the four actuators vibrate at \si{250}{\hertz} during \si{150}{\ms}, then they stop for another \si{150}{\ms}.
+When it hovers a target, it is colored and all the four actuators vibrate at \SI{50}{\hertz}.
+After \SI{1}{\ms} over the button, a ring is drawn around the cursor, and all the four actuators vibrate at \si{250}{\hertz} during \SI{150}{\ms}, then they stop for another \SI{150}{\ms}.
It warns the users that the animation is about to start.
-The animation vibrates the four actuators in a clockwise sequence at \si{250}{\hertz} during \si{200}{\ms}, followed by a \si{175}{\ms} pause.
-After this animation all the actuators vibrate at \si{250}{\hertz} for \si{200}{\ms}, then the target is activated.
-Therefore, overall users had to hover a button during \si{3}{\s} to activate it.
+The animation vibrates the four actuators in a clockwise sequence at \SI{250}{\hertz} during \si{200}{\ms}, followed by a \SI{175}{\ms} pause.
+After this animation all the actuators vibrate at \SI{250}{\hertz} for \SI{200}{\ms}, then the target is activated.
+Therefore, overall users had to hover a button during \SI{3}{\s} to activate it.
We ran an experiment with the idea to measure an increase of performance in a tactile condition over a visual condition.
This was motivated by the fact that when we tried the buttons, tactile feedback seemed to bring some benefit.
Another scenario for haptic 3D gestural interaction in this project was an open-source car racing game\footurl{https://sourceforge.net/projects/vdrift/} that I adapted for Kinect (\reffig{fig:cargame}).
The users steered the car by moving their arms like if they were holding a steering wheel.
The Kinect API computed a skeleton of the user.
-The steering angle was computed as a function of the relative position of the hands of the skeleton.
+The steering angle was computed as a function of the relative position of the hands of the skeleton, capped between \ang{-90} and \ang{90}.
+Braking was mapped to \qtyrange{15}{30}{cm} between the hands and the chest, and throttle to \qtyrange{30}{50}{cm}.
The spatial location of vibrations indicated the steering angle as shown on \reffig{fig:cargame}.
-The speed of the car was mapped to a modulation of the \si{250}{\hertz} signal with a low-frequency signal between \si{1}{\hertz} and \si{25}{\hertz} with \si{50}{\ms} durations.
+The speed of the car was mapped to a modulation of the \SI{250}{\hertz} signal with a low-frequency signal between \SI{1}{\hertz} and \SI{25}{\hertz} with \SI{50}{\ms} durations.
This modulation makes users feel like if equidistant strips covered the road.
%the faster the car goes, the frequent are the vibrations.
-In addition to this, the bottom actuator vibrated for \si{200}{\ms} at \si{100}{\hertz} when the car was braking.
+In addition to this, the bottom actuator vibrated for \SI{200}{\ms} at \SI{100}{\hertz} when the car was braking.
\input{figures/cargame.tex}
This was the same issue than with the dwell buttons.
Rather than rethinking both the inputs and outputs, my understanding at the time was that I was not measuring the right thing.
The users feedback of this first experiment suggested that the tactile sensations provided benefits in terms of realism and immersion in the game.
-Therefore I conducted another experiment, but focused on qualitative benefits.
+Therefore I conducted the following experiment, which focused on qualitative benefits.
+%In the next submission we performed a new user study and measured emotions with the PAD questionnaire (Pleasure Arousal Dominance)~\cite{mehrabian96} and presence with Witmer \etal PQ questionnaire \cite{witmer98}.
+%\paragraph{Hypotheses}
+We made the hypotheses that $H_1$ tactile feedback would increase the sensation of realism of the game because of the increased sensory stimulation; and $H_2$ tactile feedback would increase the users' sensation of control, because it provides them feedback about the way the game interpret their actions.
+
+\paragraph{Methodology}
+40 participants took part of the experiment (mean age 24.7 years).
+They were instructed to drive as many laps as possible in 10 minutes.
+They were advised to avoid going out of the road since it notably reduces the speed.
+They stood \SI{2.5}{\meter} away from the Kinect during the game.
+%Before the experiment the height of the Kinect was calibrated to make sure the participants' arms were in the sensor’s range.
+The game was displayed on a 17” laptop screen, with a $1600 \times 900$ resolution and the same sound volume was used for all subjects.
+We opted for a between subject design: half of the participants received tactile feedback ($T$), and the other half did not ($NT$).
+We explained the mapping of the tactile feedback to the participants of condition $T$.
+Tactile feedback was not mentioned to the participants of condition $WT$.
+
+Before they performed the task, the participants filled the immersion tendency questionnaire (ITQ)~\cite{witmer98}.
+It measures the ability to get involved and focused in tasks, playing habits and the tendency to get immersed in games.
+%This questionnaire identifies three factors among these items: Involvement (ability/habits to get involved in tasks), Focus (ability to stay focused on a task) and Games (playing habits and tendency to be immersed in games).
+After the experiment we measured the user’s emotional state with the Pleasure Arousal Dominance questionnaire (PAD)~\cite{mehrabian96}.
+%, which uses 7 points bipolar scales.
+We also measured spatial presence with the presence questionnaire (PQ)~[32].
+It measures the sensation of control, perception of sensations, distraction from the task, and realism.
+%This questionnaire identifies four factors among these items: Control (sensation that user’s actions have conse-quences on the virtual environment), Sensory (how much/well the user’s senses are stimulated), Distraction (how easy the user was concentrated on the task) and Real-ism (how realistic was the simulation).
+We added three additional questions about tactile feedback adapted from questions about audio feedback: 1) How much did the tactile aspects of the environment involve you? 2) How well could you identify the vibrations? 3) How well could you localize vibrations?
+We analyzed our results with T-tests, Pearson correlation and Cronbach’s alpha.
+
+\paragraph{Results}
+The reliability of the ITQ questionaire is acceptable (\cralpha{0.75}).
+Participants had a mean immersion tendency of $116.05/189$ in the $T$ condition, and $117.5/189$ in the $NT$ condition.
+We did not detect any significant effect (\pEq{0.72}).
+
+The PQ questionnaire has a good reliability in both $T$ (\cralpha{0.89}) and $NT$ (\cralpha{0.88}) conditions.
+
+Users in T condition have a 159.75/245 mean Presence score whereas users in WT condition have 142.5/245 (Fig-ure 12, left). We detected a significant difference between the two conditions (p<0.001). The analysis of the factors identified in [32] shows that there is a significant difference between sensory (p<0.001) and realism (p<0.001, Figure 12, center) factors. However we do not detect difference in control (p=0.55) and distraction (p=0.90). Moreover there is a strong positive correlation between haptic and realism items for users in T condition (r=0.54). We computed pleasure, arousal and dominance scores by adding the score of their items and mapping the result between -1 and 1. The mean pleasure score is 0.4 in the T condition and 0.36 in the WT condition. We do not detect a significant effect (p=0.76). The mean arousal score is 0.34 in the T condi-tion and 0.46 in the WT condition, with no significant difference detected (p=0.27). The dominance score was 0.32 in the T condition and 0.15 in the WT condition (Figure 12, right). We did not detect a significant difference (p=0.07, IC=[-0.01, 0.35]).
+
+Figure 12: Presence, realism and dominance in T and WT conditions.
+
+\paragraph{Discussion}
+We analyze the results with respect to hypotheses we made, and discuss the relationships between the design of our mappings and the results. We also discuss interesting points that emerged from discussions with the users.
+
+Realism
+Our first hypothesis was that tactile feedback would en-hance the realism of the game. The results shown that real-ism items of the presence questionnaire obtained better scores in the tactile condition than in the condition without tactile feedback. Moreover we found a correlation between the haptic items and the realism items for users in the T condition, which suggests a positive impact of the tactile feedback on the realism. Therefore we found support for our first hypothesis.
+The discussions we had with the users after the experiment help us to understand the explanations of this effect. Five users of the WT condition explicitly reported they did not have an impression of speed. Users in the T condition had a tactile feedback for speed. We observed users “singing” along the vibrations at high speed, and several users report-ed that tactile feedback helped them to feel the speed. These observations are not sufficient to draw a reliable assess-ment, however it gives credit to remarks made in previous research on presence in virtual environments: “The more completely and coherently all the senses are stimulated, the greater should be the capability for experiencing presence” [12], “The greater the extent of sensory information trans-mitted to appropriate sensors of the observer, the stronger the sense of presence will be” [29].
+
+Control
+Our second hypothesis was that the tactile feedback would enhance the user’s sensation of control. The results did not show significant effects on control items of the presence questionnaire, or dominance PAD questionnaire. However the dominance scores have a wide variance in the T condi-tion, which suggest that small effect may be detected with more users. Nevertheless we did not find support for our second hypothesis.
+The users’ comments during the experiment and discus-sions we had after the experiment gave us insights on the reasons of this result. Most of users reported difficulties to brake. They had to pull their hands close to their shoulders to break efficiently, and it was difficult to turn at the same time. This problem affected both conditions, and reflects the low overall score for control (mean 57.15/91).
+The other explanation is that the tactile feedback mapped to the direction intended to help the user to feel if the car reacted to her gestures. However we faced an interesting problem with the mapping we used. While users admitted they understood the speed information easily, they had difficulties to understand the orientation information and ignored it. When we explained this mapping to the user before the experiment, four users asked if this mapping was absolute or relative to the orientation of the hand. Our choice was to vibrate on the top side of the arm when the car was going straight, and the left or right side depending on the direction of the car (Figure 7). However usually when the user holds the imaginary wheel, the top side of the right arm faces the right of the user, and changes when the user turn the wheel. While we have no measure of this effect, this observation raises the importance of designing carefully the feedback mapped to the gestures performed by the user. More generally it is not clear if previous results on tactile cues [4,8,14,15,26] apply when the user focuses his attention to a complex task like playing a game. It led us to start a whole new study about this question, as a follow up to this work.
+
+General discussion
+Besides our hypotheses, we gathered various interesting remarks. Users showed interest in the tactile feedback, and suggested other mappings that they would like to have. Several users requested vibrations when they hit obstacles. While we believe this kind of feedback is interesting, it is already used in current console games with vibrating gamepads. We decided to not include existing feedback in this study to explore new kinds of feedback. One of the participants, used to play car games, would like a feedback for the accelerations (G). He believes it would add realism, sensation of speed, and help him to turn correctly. Another participant, not used to play videogames but expert in HCI, suggested providing tactile feedback more sparsely. His point is that it would make the feedback more noticeable, and the user would seek for the feedback.
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-In the next submission we performed a new user study and measured emotions with the PAD questionnaire (Pleasure Arousal Dominance)~\cite{mehrabian96} and presence with Witmer \etal PQ questionnaire \cite{witmer98}.
%, significant difference in sensory and realism factors.
projects / hdr.git / commitdiff