In recent years, VR systems have been utilized in industry,
education, entertainment and as accessibility tools.
This increasing prevalence of VR necessitates an accurate representation
of the environment to users.
Precise egocentric distance perception is one of the aspects
of an accurate representation of virtual environments
that is important for intuitive interactions.
The increasing number of VR games requiring fast movements,
walking and jumping around the room while interacting with objects
highlights the importance of a precise and intuitive representation
of a virtual environment.
However, prior research shows that people tend to underestimate
distances and virtual environments.
Many factors have been identified to have a potential effect
on distance perception in virtual environments,
including attributes such as weight, display resolution
and field of view, environmental attributes
such as indoor or outdoor, linear perspective, foreshortening
and texturing, and human attributes such as height, age
and prior virtual reality experience. However, HMDs of the past
had restricted fields of view and lower display resolution.
Today, modern HMDs such as the Pimax, use high resolution display
and a field of view which nearly matches that of human eyes field of view.
Thanks to technological advancement. This provides us with an opportunity
to study much higher fields of view than in prior work
and also to directly study the effect of field of view in an isolated manner
by simulating fields of view of the older HMDs.
In this work, we conducted such a study.
Our goal in this study is to understand the direct impact
of horizontal field of view and vertical field
of view on user distance perception.
To ensure results are general and potential field
of view effects are not bounded to one specific environment,
we tested varying field of view conditions across multiple environments,
indoor/outdoor, and cluttered/uncluttered.
In doing so, it can be understood if distance perception and effects
are specific to the field of view or if the environment
also influences distance perception.
To evaluate distance perception, we utilize a blind walking task
in which users were asked to walk towards a specified target
and the virtual environment while keeping their eyes closed.
We conducted a mixed study.
We had between subject factors, including the environment,
characteristics of indoor and outdoor included,
and uncluttered and within-subject factors were horizontal field of view,
vertical field of view and target distance.
All the environments were designed with realistic elements
and real world scales.
We simulated six different field of view combinations
programmatically in the headset.
The horizontal field of view levels were 165 degrees,
110 degrees and 45 degrees, and the vertical field of view levels
were 110 degrees and 35 degrees.
Each field of view level represents the field of view
of the real virtual reality HMD, the Pimax or the nvisor 60.
The target distances were 3, 4, 5 and 6 meters away from the participants.
Each condition was performed three times by each user
and the main error was recorded.
This resulted in 72 total trials.
The final participant pool consisted of 56 users.
11 of them were female.
We used the Pimax 5k plus headset with a field view
of 165 by 110 degrees.
The headset was connected to an HP Z backpack.
We also included a small speaker that rested on the backpack
behind the participants head provide auditory feedback during the study.
After wearing and adjusting the headset and the backpack computer,
the participant was asked to stand at the starting point
in the room to start the trials.
The participant looked at the environment and estimated their distance
through the target.
They then closed their eyes and let the researcher
know that they were ready.
The researcher started the walk procedure by pressing a key on the wireless keyboard
which turned the display black, and a faint computer voice
from the backpack was played which told the participant to "go".
This was to simulate blindfolding the user.
As for previous experiments, the user started to walk and stopped
when they thought they reached the target and let the researcher know verbally.
The researcher then pressed a button on keyboard
to record the user's location.
Play faint computer voice said: "done" to let the user know
they can open their eyes and reveal a guidance arrow
under the participants feet to navigate the user
back to the starting position.
We use this guidance arrow, which was always fixed under the feet
and pointed to the starting location.
The user should have walked towards the arrow's direction
when they reached a start location.
Another arrow showed them the correct direction.
The researcher then pressed the key on the keyboard
and the virtual environment would then reappear.
The next trial then began.
We found a significant main effect of horizontal field
of view on distance judgments.
Post-hoc comparisons revealed a statistically
significant difference between 165 and 45 degrees,
as well as a significant difference between 165 and 110 degrees,
such that participants were more accurate where their distance estimations
with a larger horizontal field of view conditions.
We did not find a significant main effect of vertical field
of view on distance judgments.
We found a significant interaction effect between horizontal
and vertical fields of view, a post-hoc comparison
revealed when the horizontal and vertical field of view
were both 110 degrees, users performed significantly worse
than the 110 by 35 degree level.
This unexpected result happened to occur when the displayed field view was square,
whereas all other field of view combinations
in our study were rectangular.
While we are unaware of any literature that might explain this finding,
it could be in part due to natural human site
not having equal horizontal a vertical angles.
We found a significant main effect of clutterdness on distance judgments
so that the participants had greater underestimation
in uncluttered environments compared to cluttered environments
and we found a significant main effect of environment type.
The participants tended to have larger under estimation
of distances in outdoor environments compared to the indoor environments.
We did not find a significant interaction between clutteredness
and indoor and outdoor, which shows independent effect
of indoor/outdoor and cluttered/uncluttered
on distance judgment within our selected environments.
Expectedly, we found a significant manufact of distance
such that the further the target, the greater the under estimation.
We did not find a significant interaction effect between distance
and horizontal field of view or distance and vertical field of view.
While we found a significant interaction effect between distance
and indoor/outdoor, we did not find a significant interaction
effect between distance and clutteredness.
Our results indicate that wider horizontal fields of view
yield more accurate estimations of short range distances
in virtual reality, where previous work did not find field of view
to be a significant factor.
Our work is the first to isolate horizontal field of view
while keeping all other apparatus attributes constant,
and it does show how field of view is main factor to be considered.
One unexpected result of our study was that vertical field of view
did not have a significant effect on distant judgments.
The two levels of vertical field of view were so vastly different
that we anticipated to show how taller fields of view
were superior to shorter ones, but it seems
that this is not necessarily true.
Current hardware may already support the levels of vertical field of view
that are necessary to accurately perceive a given virtual environment and, as such,
we would expect hardware designers to strictly focus
on horizontal field of view extensions.
However, although we have shown how distance estimation
does not improve with taller fields of view,
it is likely the case that other metrics not measured in our study,
such as task performance, presence and enjoyment,
could improve with the extension of vertical field view.
Our study strictly speaks to distance perception.
We found a significant difference between cluttered
and uncluttered environments, such that the participants
tended to underestimate distances significantly
in uncluttered environments versus cluttered.
This shows that environment clutteredness or the presence of familiar objects
that the user can use to grasp a sense of scale
affects the perception of distance.
This improvement in this judgment in closed environments
may be related to the number of objects present in the scene
and the visual depth cues they provide to the users.
While there is ongoing discussion regarding the direct effects
of static and environmental elements providing reliable visual anchor.
Our results also revealed that being in an indoor environment
significantly improves distance judgment, and this is most likely
due to the walls of the indoor space providing some visual cues
regarding the environment size.
We find that this effect of being enclosed a walled environment and familiarity
with the building blocks of an indoor environment
does substantially enhance one's ability to judge distances
regarding that environment.
These trade-offs may need to be considered when the perception of distance
is of importance in a virtual reality system design.