CHI 2018 Late-Breaking Abstract

CHI 2018, April 21–26, 2018, Montréal, QC, Canada

VR Reading UIs: Assessing Text
Parameters for Reading in VR
Tilman Dingler
University of Melbourne
Melbourne, Australia
tilman.dingler@unimelb.edu.au

Kai Kunze
Keio University Graduate Schoolof Media Design
Yokohama, Japan
kai@kmd.keio.ac.jp

Benjamin Outram
Keio University Graduate Schoolof Media Design
Yokohama, Japan
benjamin.outram@gmail.com

Abstract
Virtual Reality (VR) devices have increasingly sparked
both commercial and academic interest. While applications
range from immersive games to real-world simulations, little attention has been given to the display of text in virtualenvironments. Since reading remains to be a crucial activity to consume information in the real and digital world, we
set out to investigate user interfaces for reading in VR. To
explore comfortable reading settings, we conducted a user
study with 18 participants focusing on parameters, such as
text size, convergence, as well as view box dimensions andpositioning. This paper presents the first step in our work
towards guidelines for effectively displaying text in VR.

Author Keywords
Reading; Virtual Reality; Text Parameters; Reading Comfort

ACM Classification Keywords
H.5.m [Information interfaces and presentation (e.g., HCI)]:
Miscellaneous
Permission to make digital or hard copies of part or all of this work for personal orclassroom use is granted without fee provided that copies are not made or distributedfor profit or commercial advantage and that copies bear this notice and the full citationon the first page. Copyrights for third-party components of this work must be honored.
For all other uses, contact the owner/author(s).
Copyright held by the owner/author(s).
CHI’18 Extended Abstracts, April 21–26, 2018, Montreal, QC, Canada
ACM 978-1-4503-5621-3/18/04.
https://doi.org/10.1145/3170427.3188695

Motivation and BackgroundAs more and more VR systems enter the consumer market, developers and designers create an increasing set ofgames, applications, and utilities. Slowly, those creators lay
the foundations for User Interface (UI) design patterns in
VR. While the big advantage of VR lies in the immersive-

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ness through a multimodal presentation, text remains animportant modality to convey information [7] as it is one of
the most common and prominent ways to acquire knowledge. There are text layout, legibility, font and other guidelines for most major display and device types, from regular monitors to non-rectangular displays, desktops, smartphones, and watches [3].
Figure 1: Screenshot of thereading UI for setting preferredparameters.

Early work by Duchnicky and Kolers [5], for example, focused on the effect of window height and line width onreading performance. Especially for smaller window sizes,
they concluded four lines of text to be optimal, whereas only
two lines had a negative effect on readers. Bernard et al. [1,2] also explored a number of parameters to support legibility, such as font size and font family. Rello et al. [8] investigated different font sizes for the body of websites. Using an
eye tracker and comprehension tests, they found that readability and text comprehension significantly improves when
online text is displayed with larger font sizes, namely 18, 22,
and 26.
Reading in VR, however, has so far only been sparsely researched [6]. Sousa et al. [10] investigated ambient lighting
conditions for when radiologists analyzed and interpreted
images. Using VR headsets they report diminishes the effects of unsuitable ambient conditions. Grout et al. [6] focused specifically on reading tasks with Head-Mounted Displays (HMDs) examining different aspect ratios and comparing plane vs. curved displays. Studies with extensive
reading parameter variations in VR, however, seem to belacking. For designers to create immersive, yet comfortableand effective reading experiences, we need to assess somebasic text and UI parameters first.

tent screen layout system that can be applied to any screen
at any distance. The human eye can comfortably cover a
viewing angle of about 60◦ both horizontally and vertically,so primary UI elements should be kept in this area whenhead rotation is to be avoided [4]. Neck rotations, on theother hand, can increase this viewing angle to about 120◦ .
Companies, such as Google or Unity, informally release
their best practices with regard to text presentation online,
but a set of comprehensive guidelines for displaying text in
VR is yet missing. In our current work, we conduct a seriesof studies to elicit reading guidelines in VR. In this paper,
we present a first user study focusing on comfort levels ofdifferent text parameters, such as text size, vergence settings, and text box dimensions.

MethodTo define reading parameters for maximizing reading comfort, we conducted a first lab experiment with a focus on the
font, vergence, and view box adjustments. We, therefore,
allowed participants to adjust their preferred text parameter settings and asked them to state their preferences withregard to text display in a semi-structured interview.
Through University mailing lists and social networks, we
recruited 18 participants (8 female) with backgrounds incomputer science, design, linguistic, and psychology. Fiveparticipants wore contact lenses, five wore glasses, whileeight did not require any vision correction. Most of them
indicated to regularly read on their phone (15), on printed
media (14), on a PC (12), e-reader (4), or tablet (3). Whileseven participants said they frequently used a VR headset,
ten had used one once or twice before, and one participant
even owned one.

At the 2017 Google IO, Google engineers introduced a
new unit for perceived size in VR, which they called ’dmm’(distance-independent millimeter). It allows for a consis-

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Apparatus
We used an Oculus Rift CV1 HMD, with 6 degrees-offreedom (DOF) tracking (3 rotational, 3 spatial). According
to the Oculus developer documentation 1 , the Oculus Rift
CV1 has optics equivalent to looking at a screen approximately 1.3m away. We simulated the Virtual Environment(VE) using a Windows 10 PC with an Intel CORE i7 and
GeForce GTX 1060 graphics card. For user input, we used
an Xbox controller. The VE was developed in Unity 3D andthe Oculus SDK. It showed a soft dark background consisting of a space scene (see Figure 1). We used the sans-serif
Ariel font throughout the experiment. Our custom-built program recorded participant’s preference data including text
size, distance, text box size, and explicit preferences.
Figure 2: Study participant setting
her preferred text parameters.

Procedure
We invited participants to our lab and instructed them on
the purpose of the study. After signing a consent form, we
handed out a short demographic survey and introduced thestudy contents. Participants then put on the Oculus headset, made sure that the device was placed comfortably, andmodified the focus using the adjustment slider until a showntext was displayed sharply. The headset provided enoughspace for users to wear their eyeglasses inside. We started
the study by presenting a standard text with either a fixed
font size or a fixed distance. We were interested in the threevariables font size, vergence distance, and angular size,
which are all related to each other. We, therefore, studied
participants’ preferences for each variable by keeping one
variable fixed and allowing participants to control another.
The size and distance to the text were set randomly within
ranges (distance between 0.2m and 90m, and 0.09m and1.8m in absolute text height). From this starting point, participants used an XBox controller to adjust one of either the
text size or the distance to the text, until the angular size1of the text was deemed optimally comfortable for reading.
This task was repeated 5 times. Next, we wanted to determine the most comfortable convergence distance to thetext, given a fixed angular size of the text. The angular text
size determined from the mean size-distance ratio of thesize-distance pairs of data taken in the previous part of theexperiment. While keeping the angular text size fixed, theconvergence distance was set randomly within the same
distance ranges (0.2m and 90m). Participants could thenadjust the convergence to the most comfortable distance.
We also asked them to select convergence distances representing the closest comfortable distance, and the farthest
comfortable distance. Having determined participants’ preference for angular size and convergence distance, we fixed
those parameters and allowed the user to adjust the text
box width and the number of lines of the visible text, i.e.,the view box. Finally, we asked participants to record theirpreference according to three UI parameters: dark vs. lightbackground color, serif vs. sans-serif font, and the vertical
position of the view box.

Results
In the following, we present the results of the user-definedsettings grouped into angular height, vergence, view box
dimensions, its positioning, as well as the UI parameters.
Angular Height
Angular size is generally given in degrees, but we refer to it
in Google’s unit of angular size—dmm: distance-independent
millimeter—where 1dmm = 1mm height at 1m viewing
distance. The preferred height was 32 + / − 11dmm.
Vergence Distance to Text
With height set fixed, user’s selection of most comfortablevergence distance are shown in Figure 3. From this, wederived equations 1 and 2.

https://developer.oculus.com/

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Text Feature

Preference

dark vs. light backgroundsans-serif vs. serif fontvertical text box position

13 of 18
14 of 18
-1.0 +/- 2.6 deg

Table 1: Summary of text features and participants’ UI parameter
preferences.

Figure 3: All preferred vergence
distance measurements shown inorder of increasing vergence
distance. Note the logarithmic
scale on the vertical axis.

View Box Parameters
Preferences of text box width and height are shown in Figure 4. The preferred height of the text box was 7.3 ± 1.7
lines and the preferred width was 40 ± 6.5 characters. The
preferred vertical position was −1.0 ± 2.6 degrees from thehorizontal, corresponding a small movement down of thecenter of the text box.
Text Font and BackgroundA majority of 13 out of 18 participants (72.2%) preferred
white text on a black background as opposed to black text
on a white background (see Table 1). 14 of the 18 participants (77.8%) preferred sans-serif Arial text compared toserif Times New Roman fonts.

Implications and Discussion
Figure 4: Preferred width andheight of the text box viewed in thevirtual environment by participants.

In our study, we explored font size, vergence, and view box
dimension for comfortable reading in VR. While it is worthwhile investigating the effects of these parameters whenreading for an extended amount of time, this study is a firststep in form of a user-defined exploration of text parameters in VR. Table 2 summarizes our results giving the corresponding sizes based on the different measures of text
size.
The Oculus Rift CV1 HMD used in the study has a fixed
focus distance, equivalent to viewing a screen at approximately 1.3 meters. A mismatch between the vergence

Heightparameter

Preferred
size (dmm)

Preferred
size (degrees)

x-sizecapital heightbody height

23 ± 7.832 ± 1141 ± 141.3 ± 0.44
1.8 ± 0.61
2.3 ± 0.77

Table 2: Summary of preferred text angular height parameters forAriel font. Angular size is given in degrees and Google’s unit ofangular size where 1dmm = 1mm height at 1m viewing
distance.

distance and the focus distance commonly referred to asvergence-accomodation mismatch, is known to lead to discomfort and fatigue [9]. We, therefore, expected users’ preferences for vergence distance not to stray too far from the
HMD’s focus of 1.3m. Shibata et al. [9] investigated acceptable ranges of vergence-accommodation mismatch to avoid
such discomfort. From their original heuristic relations we
can derive appropriate vergence distances:dv min =df mnear
1 − Tnear df(1)

dv max =df mfar1 − Tfar df(2)Here, dv is the vergence distance, df is the effective distance to the display (the focus distance), and mnear =1.035, Tnear = −0.626, mfar = 1.129 and Tfar = 0.442 are
the slopes and intercepts of the upper and lower bounds ofvergence-accommodation comfort when considering vergence and focus in diopters (inverse units), which were determined empirically [9]. These relations give the maximum
and minimum comfortable vergence distances for a given
focus distance. In the case of the Oculus cV1, df = 1.3m,

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lower quartile
medianupper quartile

Closestdistance

Most
comfortable

Farthest
distance

0.61
0.89
1.5

1.3
2.7
8.6

2.6
9.8
64

Table 3: Summary of convergence distance (meters) chosen byparticipants.

larger displays placed farther away from the user may be
more pronounced.

Figure 5: Vergence distances elicited throughout our study as a
guideline for text display in VR. Distances are to scale.

which yields maximum and minimum convergence distances of dv (max) = 3.45m and dv (min) = 0.74m.
This corresponds also to Oculus’ guidelines for developers, who derived them from the same source. We find thatthe closest comfortable distance derived from the guidelines or 3.45m shows agreement with what was indicatedby participants in our study shown in Table 3. We find, however, that 59% of the time, participants selected a convergence greater than 3.45m as their “most comfortable vergence distance for reading”. In addition, 67% of participants
indicated vergence distances greater than 3.45m when
asked to select the “farthest comfortable distance”. This indicates that our participants tended to opt for a vergence
distance not only farther than the focal distance, but farther
than what is considered comfortable limits for the vergenceaccommodation mismatch. This may show a tendency towards a preference for viewing large displays at a distance,
and with a corrected accommodation, the tendency towards

There was quite a variation in preferences within the participant sample and a large range of allowed comfortable convergence distance for displayed text. Figure 5 summarizes
the initial guidelines we derived for those designing information displays and reading platforms in virtual reality with
HMDs having fixed focus lenses of similar properties to the
Oculus CV1, which has a focal distance of 1.3m. A roughguideline is to place text with an appropriately selected angular size as discussed above at a distance of between 1
and 10 meters from the user, but ideally at around 3m.

Conclusion
This paper presents first results of our assessment of basic
text parameters for reading in VR. While we conducted auser study to explore comfort levels of parameters, such as
text size, vergence, and view box dimensions, in follow-up
studies we are planning to apply our initial results to text interfaces and measure their effect on reading comfort, text
comprehension, motion sickness, and visual fatigue. The
current set of recommendations presented acts as a reference point for our research and can be used by otherresearchers and application developers with the goal of providing effective reading experiences in VR systems.

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Acknowledgements
We thank the participants of our study and acknowledge
the financial support by JST CREST under Grant No: JPMJCR16E1.

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