Hi everyone: I am Yi-Hao Peng.
Today I am going to present WalkingVibe:
Reducing Virtual Reality Sickness and Improving Realism while walking in VR using unobtrusive head-mounted vibrotactile feedback.
This is the joint work with my advisors Prof. Neng-Hao Yu at National Taiwan University of Science and Technology
and Prof. Mike Chen at National Taiwan University.
I would also like to show my gratitude to my lab mates and collaborators across different universities.
So walking in VR has been widely adopted in many daily applications,
such as first-person shooting games,
VR touring systems
and 360-degree videos.
However, those applications might not be accessible for everyone.
Why? Well, there is one common barrier called “VR sickness” that keeps the users from enjoying the experiences.
So VR sickness is a common symptom users face while navigating in VR, which will cause people headaches or nausea and thus they would tend to end up the experiences in a short period of time.
Previous research has pointed out that the vr sickness and discomfort might be caused from the sensory mismatch between visual and vestibular system.
Studies have also shown that 80-95% of VR users experience some symptoms of sickness
So … how could tackle this well-known issue?
Well, in fact, there are couple of types of solutions that have been proposed.
The first common type of solution is called “visual modification”,
which reduce user’s field of view and optical flow around user’s periphery.
Despite the effectiveness,
studies have shown that this type of solution often degrades the sense of user’s immersion during the experience.
The second type of solution is called body movement
providing walking naturalness and thus mitigates sickness.
These techniques, however, will cause fatigue easily and limit the interactions between limbs and environment.
The third type of solution is “external stimulation” which applies visuo-vestibular recoupling approaches to employ physical stimulation around the vestibular system
which includes airflow, galvanic stimulation and bone-conducted vibration.
These previous approach still are either limited to certain type of application scenario such as biking
or brought discomfort for the users due to the selected level and type of stimulation.
To provide better unobtrusive stimulation solution
In last year IEEE VR,
our team introduced PhantomLegs,
the head-worn haptic devices that applies alternating tapping cues that are synchronized to users’ footsteps in VR.
As users navigate through a VR environment while physically being seated,
our preliminary results showed that PhantomLegs significantly reduces VR sickness while remaining comfortable to users.
However, the noise generated from the servos of that prototype were noticeable
and had affected the VR walking experiences.
In addition, its servo-based design contributed significant bulk and weight relative to the VR headset.
Therefore, we ask ourselves if there is a more non-intrusive and easily integrated solution.
In this work, we proposed WalkingVibe, which applies unobtrusive vibrotactile feedback using integrated, light-weighted vibration motor system for VR walking experiences.
This kind of design meets our initial goal on making feedback non-intrusive and can be easily integrated.
To balance effectiveness with unobtrusiveness,
we set the vibration frequencies to about 150 Hz that provides reasonable vestibular response and low perceived annoyance.
Our initial idea is to provide vibrotactile feedback near user’s vestibular system and synchronize the feedback with user’s virtual step.
Then, we found out there are more designs need to be explored for our ultimate goal:
reduce VR sickness and improve realism for VR walking experience
To better explore possible designs,
we include two factors - placement and synchronization to form total 4 design combinations.
For placement, we consider two-sided placement, which paired vibrators are placed near user’s vestibular system,
and back side placement, which only one vibrator placed on the user’s back of neck.
For synchronization, we consider the alignment between vibrations and the user’s virtual steps.
The user’s step are represented as head-bobbing visual effect in the VR environment and we include both synchronized and random pattern in our designs.
So here is the demonstration of 2-sided synchronized vibration.
Here is 2-sided random vibration.
Here is synchronized backside vibration.
And the last one, random backside vibration.
To fully evaluate how our vibrotactile feedback affect user’s VR walking experience,
we conducted the users study to compare our proposed designs with four baseline conditions
that are made up of different visual, audio and haptic feedback.
The baseline conditions were:
visual-only without head-bobbing pattern, which the users basically shift during walking experience.
visual-only condition, which the head-bobbing pattern is applied as user’s virtual steps
Audio condition, which the step sounds are synchronized with visual-head bobbing pattern
And tapping condition, which is the two-sided synchronized tapping feedback we proposed in PhantomLegs project.
In total, there are eight study feedback compared in our study,
with 4 baseline and 4 walkingvibe design conditions.
During the experiment, participants were seated statically and passively walked through the VR environment.
The study decision for using a passive walking approach stemmed from insights in the literature that this
that approach could induce stronger rates of sickness.
The passive control has also been widely used in many VR scenarios,
including 360◦ videos and VR experiences at theme parks.
We chose seated as scenario is because many prior works studying on VR sickness chose such study settings.
Due to the number of conditions we have, we chose between-subject comparison on 8 total conditions along with 30 participants for each condition.
During the study, participants were asked to walk through consecutive check points in 9 minutes.
There are three different scene shown in the study - the city, the forest and the sci-fi passage.
Three different walking speeds are applied in turn during the VR walking experience.
For our study’s measurements, we conducted three different questionnaires throughout the experiment.
The first measurement was the discomfort score, which the users continuously reported their discomfort level every 20 seconds during the study.
Higher scores means higher discomfort they perceived.
The second measurement was simulator sickness questionnaire, which was widely adopted by many VR sickness studies.
We asked users to fill up the questionnaire before and after the study to calculate the relative sickness scores.
The last measurement was user’s perceived walking realism,
which the user rated the similarity between their VR and physical walking experiences.
We report the results for the three measurements as follow:
For the perceived discomfort during the study,
we found that 2-sided synchronized vibration let users perceived significantly less discomfort compared to all other conditions.
Besides that, 2-sided tapping feedback had significantly lower discomfort than visual-only (without head-bobbing) feedback.
As for the reported relative sickness score,
three tactile conditions included tapping and two-sided vibration feedbacks significantly reduced participants’ VR sickness
— compared with two visual-only (with and without head-bobbing) and audio conditions.
In order to further analyze the effect of our proposed design factors from the vibrotactile feedback
including the placement and synchronization factors,
we ran a mixed-factor 2 × 2 ANOVA on the relative sickness score for the factors of visual-tactile alignment and tactile placement.
Our results showed that two-sided vibrotactile feedback received lower relative sickness score compared to backside stimulation,
while the synchronization between visual and tactile feedback did not show any significant effect.
Some comments were mentioned to be the explanation for the effectiveness of our proposed technique.
“The haptic feedback on both sides can make me feel better because it is similar with what I experience while walking in real life.”
“It seemed like I was getting massaged while walking [using WalkingVibe], which felt really comfortable and thus reduce my sickness.”
Besides the results of discomfort and VR sickness,
we also discovered that two-sided synchronized vibration and audio feedback provided significantly higher walking realism
compared to all other tactile and visual-only without head-bobbing condition.
Several feedback related to realism from the users aligned with the quantitative results we got.
“The vibrotactile feedback that matched with the visual bobbing gave me a sense of walking in the environment"
“The audio [that the servo motors of PhantomLegs] made it sound like it was a robot walking instead of me”
“I think I could easily ignore the haptic feedback [from the backside vibration] after getting used to it, due to the regular stimuli that was received.”
Based on the qualitative and quantitative results,
we recommend that WalkingVibe with a 2-sided step-synchronization vibration design as the most effective technique.
Since such feedback improves users’ VR walking experiences,
not only in consideration of mitigating VR sickness and discomfort, but also in enhancing perceived realism.
Despite the effectiveness we discovered,
we should still address that there were still several study limitations in this work.
Due to the large number of study conditions and the already large scale of our study,
we did not get to explore active vs. passive control and seated vs. standing conditions,
as those would double and quadruple the study size.
Further more, the between-subject study design also limited the opportunity for the direct comparison on each feedback for the same targeted sample.
Lastly, the time that we gave to users for experiencing VR walking was still limited.
A longitudinal experience study on how each feedback affects VR sickness and discomfort across hours or days remains a future task for exploration.
So to conclude this talk, I would like to talk a little bit about our vision and future research direction.
Last year, we presented Phantomlegs, a head-worn haptic devices that synchronized tapping feedback with VR walking steps,
and found out such feedback could effectively reduce user’s VR sickness.
This year, we extend the idea of using haptics to enhance VR walking experience by applying unobtrusive vibrotactile feedback on head.
We then discovered that two-sided synchronized vibrations feedback not only reduce user’s VR sickness and discomfort, but also improve the perceived walking realism.
We envision similar feedback mechanism to better enhance other virtual experiences such as VR driving or surfing games,
and would like to explore the spectrum of haptics to further create more comfortable and realistic VR experiences.
And that’s the end of my talk.
Thanks for listening.
If you had further questions, please contact me via my personal email, and I am happy to answer any kind of questions
Thank you!