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tangible -> real

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Erwan Normand
2024-10-12 15:24:56 +02:00
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2-perception/vhar-textures/2-experiment.tex
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\section{User Study}
\label{experiment}
%The user study aimed at analyzing the user perception of tangible surfaces when augmented through a visuo-haptic texture using \AR and vibrotactile haptic feedback provided on the finger touching the surfaces.
%The user study aimed at analyzing the user perception of real surfaces when augmented through a visuo-haptic texture using \AR and vibrotactile haptic feedback provided on the finger touching the surfaces.
%Nine representative visuo-haptic texture pairs from the \HaTT database \cite{culbertson2014one} were investigated in two tasks:
%\begin{enumerate}
% \item \level{Matching} task: participants had to find the haptic texture that best matched a given visual texture; and
@@ -13,7 +13,7 @@
\label{textures}
The 100 visuo-haptic texture pairs of the \HaTT database \cite{culbertson2014one} were preliminary tested and compared using the apparatus described in \secref{apparatus} to select the most representative textures for the user study.
% visuo-haptic system presented in \chapref{vhar_system}, and with the vibrotactile haptic feedback provided on the middle-phalanx of the finger touching a tangible surface. on the finger on a tangible surface
% visuo-haptic system presented in \chapref{vhar_system}, and with the vibrotactile haptic feedback provided on the middle-phalanx of the finger touching a real surface. on the finger on a real surface
These texture models were chosen as they are visuo-haptic representations of a wide range of real textures that are publicly available online.
Nine texture pairs were selected (\figref{experiment/textures}) to cover various perceived roughness, from rough to smooth, as named on the database: \level{Metal Mesh}, \level{Sandpaper~100}, \level{Brick~2}, \level{Cork}, \level{Sandpaper~320}, \level{Velcro Hooks}, \level{Plastic Mesh~1}, \level{Terra Cotta}, \level{Coffee Filter}.
All these visual and haptic textures are isotropic: their rendering (appearance or roughness) is the same whatever the direction of the movement on the surface, \ie there are no local deformations (holes, bumps, or breaks).
@@ -24,11 +24,11 @@ All these visual and haptic textures are isotropic: their rendering (appearance
\figref{experiment/setup} shows the experimental setup, and \figref{experiment/view} the first person view of participants during the user study.
The user study was held in a quiet room with no windows, with one light source of \qty{800}{\lumen} placed \qty{70}{\cm} above the table.
Nine \qty{5}{\cm} square cardboards with smooth, white melamine surface, arranged in a \numproduct{3 x 3} grid, were used as real tangible surfaces to augment.
Nine \qty{5}{\cm} square cardboards with smooth, white melamine surface, arranged in a \numproduct{3 x 3} grid, were used as real surfaces to augment.
Their poses were estimated with three \qty{2}{\cm} AprilTag fiducial markers glued on the surfaces grid.
Similarly, a \qty{2}{\cm} fiducial marker was glued on top of the vibrotactile actuator to detect the finger pose.
Positioned \qty{20}{\cm} above the surfaces, a webcam (StreamCam, Logitech) filmed the markers to track finger movements relative to the surfaces, as described in \secref[vhar_system]{virtual_real_alignment}.
The visual textures were displayed on the tangible surfaces using the \OST-\AR headset Microsoft HoloLens~2 running a custom application at \qty{60}{FPS} made with Unity 2021.1 and Mixed Reality Toolkit (MRTK) 2.7.2.
The visual textures were displayed on the real surfaces using the \OST-\AR headset Microsoft HoloLens~2 running a custom application at \qty{60}{FPS} made with Unity 2021.1 and Mixed Reality Toolkit (MRTK) 2.7.2.
A set of empirical tests enabled us to choose the best rendering characteristics in terms of transparency and brightness for the visual textures, that were used throughout the user study.
When a virtual haptic texture was touched, a \qty{48}{kHz} audio signal was generated using the rendering procedure described in \cite{culbertson2014modeling} from the corresponding \HaTT haptic texture model and the measured tangential speed of the finger (\secref[vhar_system]{texture_generation}).
@@ -44,7 +44,7 @@ The vibrotactile voice-coil actuator (HapCoil-One, Actronika) was firmly attache
\item The nine visuo-haptic textures used in the user study, selected from the \HaTT database \cite{culbertson2014one}.
The texture names were never shown, to prevent the use of the user's visual or haptic memory of the textures.
\item Experimental setup.
Participant sat in front of the tangible surfaces, which were augmented with visual textures displayed by the Microsoft HoloLens~2 \AR headset and haptic roughness textures rendered by the vibrotactile haptic device placed on the middle index phalanx.
Participant sat in front of the real surfaces, which were augmented with visual textures displayed by the Microsoft HoloLens~2 \AR headset and haptic roughness textures rendered by the vibrotactile haptic device placed on the middle index phalanx.
A webcam above the surfaces tracked the finger movements.
]
\subfig[0.49]{experiment/textures}
@@ -58,12 +58,12 @@ Participants were first given written instructions about the experimental setup,
Then, after having signed an informed consent form, they were asked to seat in front of the table with the experimental setup and to wear the \AR headset.
%The experimenter firmly attached the plastic shell encasing the vibrotactile actuator to the middle index phalanx of their dominant hand.
As the haptic textures generated no audible noise, participants did not wear any noise reduction headphones.
A calibration of both the HoloLens~2 and the hand tracking was performed to ensure the correct alignment of the visual and haptic textures on the tangible surfaces.
A calibration of both the HoloLens~2 and the hand tracking was performed to ensure the correct alignment of the visual and haptic textures on the real surfaces.
Finally, participants familiarized with the augmented surface in a \qty{2}{min} training session with textures different from the ones used in the user study.
Participants started with the \level{Matching} task.
They were informed that the user study involved nine pairs of corresponding visual and haptic textures that were separated and shuffled.
On each trial, the same visual texture was displayed on the nine tangible surfaces, while the nine haptic textures were rendered on only one of the surfaces at a time, \ie all surfaces were augmented by the same visual texture, but each surface was augmented by a different haptic texture.
On each trial, the same visual texture was displayed on the nine real surfaces, while the nine haptic textures were rendered on only one of the surfaces at a time, \ie all surfaces were augmented by the same visual texture, but each surface was augmented by a different haptic texture.
The placement of the haptic textures was randomized before each trial.
Participants were instructed to look closely at the details of the visual textures and explore the haptic textures with a constant pressure and various speeds to find the haptic texture that best matched the visual texture, \ie choose the surface with the most coherent visual-haptic texture pair.
The texture names were never given or shown to prevent the use of visual or haptic memory of the textures, nor a definition of what roughness is was given, to let participants complete the task as naturally as possible, similarly to \textcite{bergmanntiest2007haptic}.