AnyOrbit: Orbital navigation in virtual environments with
eye-tracking
Benjamin I. Outram
Yun Suen Pai

Tanner Person
Kouta Minamizawa

benjamin.outram@gmail.com
yspai1412@gmail.com
Keio University Graduate School ofMedia Design

tannerperson@gmail.com
kouta@kmd.keio.ac.jp
Keio University Graduate School ofMedia Design

ABSTRACT
Gaze-based interactions promise to be fast, intuitive and effective incontrolling virtual and augmented environments. Yet, there is stilla lack of usable 3D navigation and observation techniques. In thiswork: 1) We introduce a highly advantageous orbital navigation
technique, AnyOrbit, providing an intuitive and hands-free methodof observation in virtual environments that uses eye-tracking tocontrol the orbital center of movement; 2) The versatility of the technique is demonstrated with several control schemes and use-cases
in virtual/augmented reality head-mounted-display and desktop
setups, including observation of 3D astronomical data and spectator
sports.

CCS CONCEPTS• Human-centered computing → Interaction design theory, concepts and paradigms;

KEYWORDS
eye tracking, 3D user interface, 3D navigation, orbiting, orbital
mode, virtual reality, augmented reality
ACM Reference Format:
Benjamin I. Outram, Yun Suen Pai, Tanner Person, Kouta Minamizawa,
and Kai Kunze. 2018. AnyOrbit: Orbital navigation in virtual environmentswith eye-tracking. In ETRA ’18: 2018 Symposium on Eye Tracking Researchand Applications, June 14–17, 2018, Warsaw, Poland. ACM, New York, NY,
USA, 5 pages. https://doi.org/10.1145/3204493.3204555

1

INTRODUCTION

With eye muscles being extremely fast and precise, gaze-based
interactions seem a natural, efficient way for human-computerinteraction tasks [Hansen et al. 2014; Majaranta and Bulling 2014].
Despite their potential, they are still not widely used. One huge
issue is the high number of unintended activations, also known
as Midas Touch problem [Jacob and Stellmach 2016]. Two otherprevalent problems are eye fatigue and, especially for navigation
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https://doi.org/10.1145/3204493.3204555

Kai Kunzekai.kunze@gmail.com
Keio University Graduate School ofMedia Designtasks, simulator/motion sickness [Mardanbegi and Hansen 2011;
Stellmach and Dachselt 2012].
Common solutions utilize eye gestures that are very different
from everyday gaze, employ multimodal interactions or rely onsmooth pursuit (the user follows a specific moving object on screen)[Esteves et al. 2015; Heikkilä and Räihä 2012; Meena et al. 2017].
Other innovative approaches use prediction algorithms to decideif a user wants to interact with or just see an object [Bednarik
et al. 2012]. We present a novel gaze-based interaction in which
we combine eye gaze with motion (in particular head motion) for
navigation. It follows work from Mardanbegi et al. extending a
combination of head and eye gaze interaction from just 1D volume control and paging [Mardanbegi et al. 2012] to unconstrained
movement in 3D space. The user can look around naturally andwill activate the gaze-based interaction as soon as he moves a bodypart (implemented on mouse and head movement).
Our approach uses an algorithm that positions the camera invirtual space on an orbital path around points of interest (POIs)
which are selected with eye-tracking. Orbital motion is ubiquitousin computer-aided design (CAD) software systems, is instantly intuitive, and particularly suited to observational tasks [Khan et al.
2005; Ortega et al. 2015]. Perspective selection around an object
can be achieved much faster and with less effort than conventional‘flying’ metaphors, while maintaining the POI in sight at all times[Koller et al. 1996]. Head rotation was the preferred method out ofseveral alternatives in a movement and observation task [Chungand Chung 1994]. Orbit-like motion is similar to fly-by camera
shots in film and sports coverage and to strafe-and-shoot strategies in first-person-shooter (FPS) video games. In addition there
is a tendency towards 3D and free-viewpoint video formats andtechnologies [Smolic et al. 2006].
We, therefore, propose that the use of orbital motion controlled
by head-rotation and eye gaze can be exploited to provide a navigation strategy with several key advantages: 1) It allows continuous
movement and 2) it is suitable to many use-cases in which orbitaland sideways type motion is already employed.
Here we describe AnyOrbit, which exploits the geometry of
toroids to allow ideal spiral paths to orbits around new POIs, allowing 6 degree-of-freedom (DOF) movement. Using eye-tracking, the
POI is determined by the user’s gaze. Finally, we explore a variety
of use cases, which indicate that the use of eye-tracking for controlling the center of rotation provides a powerful technique fornavigation and observation.

ETRA ’18, June 14–17, 2018, Warsaw, Poland

2

B. Outram et al.

ANYORBIT

Orbital techniques generally provide 3DOF of movement (two orbital directions and one radial direction), which limits the user’sview to only the radial direction in towards the center. Orbital techniques are often then combined with flying, panning and other‘modes’ that can be switched between [Fitzmaurice et al. 2008; Tanet al. 2001; Zeleznik and Forsberg 1999] to allow other types of
movement and 6DOF navigation. These methods work well for
desktop CAD applications, but within an immersive virtual environment (VE) context, panning and other types of motion are
known to cause excessive motion sickness [Chen et al. 2011; Pauschet al. 1993; Psotka 1995; Stanney and Hash 1998].
To overcome this problem, Koller et al. suggests allowing the user
to switch between traditional ego-centered rotation, and orbital
viewing modes [Koller et al. 1996]. While in the ego-centered view,
the user can select an object of interest to become the orbital centerusing a peripheral input method such as a control stick. The user isthen teleported to a location determined by their current rotation
angle, the current radius between the user and the object, and the
new selected center of orbit, or alternatively the user is locked suchthat their forward-facing vector is no longer facing the center ofthe orbital motion. The problem is that teleportation is sometimes
disorientating, and facing towards any direction other than towards
the center of rotation is uncomfortable.
AnyOrbit solves these problems by providing an all-in-one modethat can reproduce both ego-centered and orbit-like movement at
appropriate times. For example, if the POI is in the peripheral vision,
the user’s intent is likely to look towards the POI in an ego-centeredfashion, before choosing to orbit around it.
With AnyOrbit, we automate this process by taking the relative
position of the POI in the field of view (FOV) as an input to determine the type of motion. We can think of ego-centered and orbital
modes as being two ends of a continuum of behaviour between
cases where the radius of curvature of the user’s motion is zero(ego-centered rotation), and where it is equal to the distance to the
POI (purely orbital). AnyOrbit alters the radius of movement on the
fly depending on where a POI is in the FOV of the user. If the POI
is in the peripheries of the FOV, we shorten the user’s movement
radius, which allows the user to first turn towards the POI, suchthat the POI moves towards the center of their FOV. As the POI
approaches the center of the FOV, we gradually lengthen the radiussuch that the user finds themselves on an orbital path looking in
towards the POI. The result is a natural and intuitive way of looking
and orbiting around VEs, in which the user in general moves on
spiral arcs between orbital paths about a changing POI.
Another related work, GazeSphere, switched between ego-centricand orbit-like motion along predefined linear paths by gazing at
specific POIs in 360-video [Pai et al. 2017]. AnyOrbit extends thisinteraction to 3-dimensional movement in 3D environments, by allowing the user free choice of POI and by improving the transitions
between ego-centered and orbital rotation.
Figure 1 (a) illustrates how the orbital motion resulting fromsuch a process creates a smooth outward spiral trajectory from thecurrent location and orientation towards a circular orbital trajectorywith the new marker location at the center. In the reverse case, inwhich the user rotates their head away from the marker, the radiusFigure 1: Illustrates the smooth path taken from one position and orientation to a position and orientation about anew orbital center. (a) and (b) show cases in which the user
rotates towards and away from a new POI respectively. The
black line indicates the path taken by the user, the red line
indicates the path taken by the dynamically controlled orbital center, and the dotted blue lines indicate the user’s
forward-facing vector and the radius at that moment. By
controlling the radius dynamically the user’s path spirals
towards the new orbital path.

is extended with the result that, again, their trajectory smoothlytransitions, this time via an inward spiral trajectory towards a
circular orbit with the marker at the center, as illustrated in 1 (b).
Since the marker could in general be at any horizontal and vertical position in the FOV, we would like to independently control bothhorizontal and vertical orbital curvatures of rotation. A sphericalorbit is problematic because it has the same curvature in both horizontal and vertical directions. Therefore, we calculate the motion
on a torus, whose radii are in general different in horizontal andvertical directions. By calculating the torus surface based on thecurrent relative positions of both the user and the orbital marker,
we can thus allow the user to smoothly move from orbit about
one center to an orbit about any POI in the user’s FOV. Whichever
way the user turns will produce an optimal smooth path to any
perspective they choose about any new POI. Next, we outline how
this process is implemented in an algorithm to calculate the newposition of the user in the 3D environment at each frame.
The technical implementation is as follows (code is available on
GitHub [Outram 2018]). A new position P in each frame is calculated
based on the following initial parameters: P 0 the position of the user
in the last frame; the azimuthal, ϕ 0 , and zenithal θ 0 angles defining
the orientation of the user in the last frame; M the position of theorbital marker relative to the user and; the current orientation of
the user, ϕ 1 and θ 1 . In addition, the fixed parameter a controls thepace at which a rotation will cause the orbital distance to reach anequilibrium with the new orbital center (we use a = 2).
In the following, x, y and z refer to left-to-right horizontal, downto-up, and straight-outward local directions relative to the user’s
current orientation (ignoring tilt about the z axis), and X , Y and Z
are right-handed world coordinates with Y in the upward direction.
In addition r x and ry refer to radii of the movement curvature in x
and y directions. The algorithm for calculating the user’s current
position is as follows:AnyOrbit: Orbital navigation in virtual environments with eye-tracking

ETRA ’18, June 14–17, 2018, Warsaw, Poland(1) Determine whether the user’s head movement relative tothe last frame is towards or away from the orbital marker inthe x direction.
(2) Calculate the radius of curvature in the x direction r x : In thecase that the user is rotating towards the marker,
r xtowards = Mz − a|M x |(1)where Mz and M x are components of M in z and x directions.
In the case that the user is rotating away from the marker,
away

rx

= Mz2 /r xtowards(2)

We also constrain r x such that 0.2 < r x /M x < 5 to limit the
maximum velocity and remove large accelerations.
(3) Repeat steps 1 and 2 for the y direction.
(4) Find the center of the torus on which we wish to move. In
the case that r x > ry , we can consider a position T (θ, ϕ, r , R)on the surface of a torus whose symmetry axis is along Y
and whose center is at the origin, defined by
Tx = − R + r cos(θ ) sin ϕ
Ty = r sin θTz = − R + r cos(θ ) cos ϕwhere Tx , Ty and Tz are the components of T in X , Y andZ -axes, r and R are the torus minor and major radii, and θ
and ϕ are zenithal and azimuthal angles relative to world
coordinates. The center of the torus on which we wish tomove is thus given by
T 0 = P 0 − T (θ, ϕ, r , R)

(3)

with θ = θ 0 , ϕ = ϕ 0 , r = ry and R = r x − ry .
(5) Finally, calculate the new position, which is given by,
P = T (θ, ϕ, r, R) + T 0(4)

this time with θ = θ 1 , ϕ = ϕ 1 , and again with r = ry andR = r x − ry .
(6) In the case that ry > r x , follow a similar process as in steps
4 and 5, but instead consider a torus whose axis of symmetry
is in the horizontal x axis of the previous frame. Since thetorus is perpendicular to the forward-facing direction of thelast position and orientation defined by ϕ 0 and θ 0 , the centercan be trivially found by extending this vector direction out
from P 0 by a distance of ry . Then for step 5, define a torus inworld coordinates with symmetry axis along X , substituteθ = θ 1 , ϕ = ϕ 1 − ϕ 0 and rotate the resultant T about theorigin by ϕ 0 .
It is helpful for user control that the marker always be not too
distant and in most cases visible [Fitzmaurice et al. 2008], and so werecommend limiting its position, depending on the environment
context, to for example Mz < 100m. If the marker is outside theFOV, we constrain ry = r x = 0, i.e. egocentric rotation.
If using a head-tracked HMD, the 3 rotational DOF are sufficient
as input to AnyOrbit, allowing it to be used with 3DOF mobile
VR headsets. If available, the extra 3 translational DOF could be
ignored, but we found it more comfortable to allow the user freetranslational movement relative to the orbital center. To achievethis, record the translational movement of the camera since the last
frame and add it to the position in step 5.

Figure 2: Shows position data of the user in the VE while
using AnyOrbit, as viewed from above, using HMD with directed movement control.

3

CONTROL SCHEMESThere are 4 control inputs of the AnyOrbit system: zenithal (pitch)
and azimuthal (yaw) angles, POI (desired orbital center) and desired
orbit radius. Here, the angles are coupled to the corresponding headrotation angles as in previous work [Chung and Chung 1994; Koller
et al. 1996]. Control of the POI and orbital radius can be achieved
with mouse, eye-tracking, or chosen by a director. A previous study
using a mouse input with AnyOrbit enabled effective navigation to
new viewpoints at a rate comparable to changes in perspective inbroadcast sport, and did not cause significant increases in simulator
sickness after the first 5 minutes [Outram et al. 2016]. Unique tothis work, we outline the technical implementation, and report on
directed control and the use of eye-tracking, which have the added
benefit of allowing hands-free interaction. Table 1 summarises thecontrol configurations, and next we describe user experience.

3.1

HMD Directed: Head Rotation with
Directed Position and Radius Control

3D film and storytelling often has the problem that the director
cannot control which direction the user is looking. StyleCam proposed a solution in which navigational control is shared between
the user and the content producer to direct the user experience[Burtnyk et al. 2002]. However with AnyOrbit, the director cancontrol the POI that the user is facing, while simultaneously giving
full rotational control to the user.
We created a VE consisting of a sample of 27,000 stars takenfrom the HYG Database [Nash 2011]. Figure 3 shows the VE, inwhich the stars’ positions, colours, brightnesses and velocities are
rendered using aesthetically chosen scaling factors. In this case, wepredefined the desired POI and orbital radius. Once a user wants tomove on, they can trigger a change to the next predetermined POI
and radius by aligning the current orbital center with a designatedpoint. User position data is shown in Figure 2. The predetermined
POIs and radii were selected to give a variety of perspectives, fromboth within the field of stars, and looking in from outside. Navigation and observation were reported to be instantly intuitive, with
one user remarking that it “feels very dramatic and gives a heightened sense of perspective”. An ideal use-case would be of consuming
sport/e-sport recorded in 3D. Broadcasters can direct the user’s
attention while the user remains in control of their rotation andperspective.

ETRA ’18, June 14–17, 2018, Warsaw, Poland

B. Outram et al.

Table 1: Various control schemes we have tried using AnyOrbit.
AnyOrbit Parameter Control Schemes

3.2

Configuration Name

Pitch

Yaw

Desired orbit radiusDesired orbit center

HMD Directed
Desktop Eye-gaze
HMD Eye-gazehead pitch
mouse yhead pitch

head yaw
mouse xhead yaw

Chosen by director
Fixed
Fixed

Chosen by director
Eye-gaze x,y
Eye-gaze x,yDesktop Eye-gaze: Mouse Rotation with
Eye Gaze Position Control

Here we explored the use of AnyOrbit in a desktop environment.
The desired orbital radius was kept fixed, while the desired orbital
center was placed at a distance from the user equal to the fixeddesired orbital radius, with the x-y position of the marker determined by the x-y on the screen of the user’s gaze. A Tobii EyeX eye
tracker was mounted at the bottom of the computer monitor facing
the user. After a brief calibration, the eye-tracking data is sent to
the Unity environment via a Tobii plugin, allowing the eye-gazedata to be used to control the POI marker.
To test the control scheme, we developed a simple environment
consisting of a ground plane with two cubes on the surface separated by some distance (see Figure 3). The user can navigate toorbital paths around either of the cubes, by simply tracking the
cubes with their eyes as they rotated the camera with the mouse.
The technique felt intuitive, and the quality of the POI following
the eye gaze position felt like magic. Users preferred not to have avisible marker that followed their gaze, saying it was too distracting.

3.3

HMD Eye-gaze: Head Rotation with
Eye-Gaze Position Control

As with the "Desktop Eye-gaze" example, we fixed the orbital radius
and used eye gaze position to control the x-y position of the AnyOrbit POI. In this case however, the environment was experienced
through an HMD and camera angle was coupled to head rotation
angle. PupilLabs eye-tracking technology was installed into an
HTC Vive headset, which required a short calibration task before
entering the VE. We tested the same star-field VE as in the "HMD
Directed". As in the desktop eye-gaze scheme, users preferred it
when the orbital marker was not visible.
Leveraging eye-gaze to control the POI marker not only frees up
the hands for non-navigation specific controls, but may also further
reduce simulator sickness. With mouse control of POI marker, theuser could be looking at a part of the VE in the foreground of theorbit center, in which the visual-field optical flow is opposite towhat would be normally expected. From previous research [Stanneyand Hash 1998], and from our experience, there is reason to believe
this could be the cause of increased simulator sickness. If the POI
marker is controlled by the eye-gaze, such a situation is avoided.
Indeed, we have only began to explore eye-gaze’s use with AnyOrbit, but our implementation points to intriguing possibilities.
It feels like the world anticipates your movement intentions, andeye-gaze control may heighten a sense of immersion. It can also
help for motor-impaired users [Jankowski and Hachet 2015].

Figure 3: VEs used in our implementation. Top: User perspective of a VE consisting of stars. The user is guided onan orbital viewing path to different POIs (see accompanying
video). The green object in the center identifies the POI andthe circle marks the desired radius. Aligning the POI withthe distant object advances to the next POI. Bottom: One of
the VEs used for demonstrating eye-gaze control of orbital
center. The user can orbit around either of the boxes by looking at them and navigate on a smooth trajectory.

4

CONCLUSION

We have described the design and implementation of AnyOrbit, atechnique for hands-free orbital navigation around and between
POIs selected by the user’s eye gaze. Several different POI control
schemes were tested, including user control through eye gaze, andalso directed control. Directed control was found to be instantly
intuitive and gives POI control to the director while not compromising on user’s freedom to rotate. Control using eye-tracking
was effective in both desktop and HMD scenarios, and allowed
surprisingly intuitive hands free navigation.
A limitation of AnyOrbit is that it is easy for users to travel
through virtual objects, which is known to be disorientating. Mitigation strategies exist which may be applied to our system [Fitzmaurice et al. 2008; Mackinlay et al. 1990; Phillips et al. 1992]. In
particular, the orbital radius could be shortened as a user approaches
an object, reducing their velocity and steering them away from virtual objects. Simulator sickness also remains a limitation of oursystem. FOV restrictors could mitigate this problem [Fernandes
and Feiner 2016].
The technique potentially leads to new types of interactive media
experience, and can be applied widely to CAD systems, sports ande-Sports, 3D recorded media, data visualisation and games.

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