Extended Walking in Room-Scale VR Via a Subtle Situation-Based Rotation of the Virtual Environment While Maintaining a Full Sense of Presence

EXAMENSARBETE INOM MEDIETEKNIK, AVANCERAD NIVÅ, 30 HP STOCKHOLM, SVERIGE 2020

Extended walking in room-scale VR via a subtle situation-based rotation of the virtual environment while maintaining a full sense of presence

JOHANNES KARLSSON

KTH SKOLAN FÖR ELEKTROTEKNIK OCH DATAVETENSKAP ABSTRACT Assuming that the emergence of inside-out positional tracking in commercially available VR systems indicate a future where room-scale VR is experienced more freely, there is a demand for adaptable and immersive VR locomotion techniques that while enabling real walking overcomes the physical restrictions of a play space without the use of additional hardware. Hence, the purpose of this study was to explore the hypothesis that a subtle situation-based rotation of the immersive virtual environment (IVE) around the user can free up physically restricted virtual space and enable extended real walking in room-scale VR, while a full sense of presence is maintained. Based on Findings of a literature study, a prototype of an adaptable and mobile locomotion technique manipulating the IVE was developed and tested using three different rotations; a baseline medium rotation, a fast and a slow, all deFined through trial and error with the capacities of freeing up restricted virtual space, and of maintaining presence, in mind. The user tests were designed as a within-subject test, aiming to expose the limits in the prototype by putting pressure on two potentially critical factors: user velocity and the capacity of freeing up restricted virtual space in all directions. The results imply that the proposed locomotion technique has the potential of extending virtual walking while maintaining a full sense of presence and that there is an optimally balanced rotation between the medium and slow rotation used in the present study. However, since the participants were not redirected enough to be preserved within the physical play space, the prototype may be used as a tool rather than as a redirecting technique.

ABSTRAKT Om man antar att utvecklingen och appliceringen av ”inside-out” positionsspårning i kommersiellt tillgängliga VR-system pekar på en framtid där room-scale VR upplevs mer fritt, så Finns det ett behov av anpassningsbara VR-rörelsetekniker som utan extra hårdvara möjliggör ett större spelutrymme ä n det fysiska spelrummet samtidigt som användaren kan förFlytta sig virtuellt genom verkliga rörelser. Syftet med denna studie var att utforska hypotesen att en subtil situationsbaserad rotation av den virtuella miljön runt användaren kan frigöra fysiskt begränsat virtuellt utrymme och samtidigt upprätthålla en känsla av full närvaro. Baserat på resultaten från en litteraturstudie utvecklades en prototyp som och testades med tre olika hastigheter; medel, snabb och långsam. Dessa var alla deFinierade genom ”trial and error” baserat på prototypens kapacitet att frigöra begränsat virtuellt utrymme och att bibehålla närvaro i åtanke. Användartesterna utformades som ”within-subject” tester med målet att exponera prototypens begrä nsningar genom att pressa två potentiellt kritiska faktorer: hastigheten användaren rörde sig i och prototypens kapacitet att frigöra begränsat virtuellt utrymme i alla riktningar. Resultaten antyder att den föreslagna rörelsetekniken har potentialen att möjliggöra ett större spelutrymme ä n det fysiska spelrummet samtidigt som en känsla av full närvaro upprätthå lls och att det Finns en optimal rotation emellan rotationerna medel och långsam. Däremot, eftersom deltagarna inte omdirigerades tillräckligt för att bevaras inom det fysiska spelrummet ä r det troligt att prototypen borde användas som ett verktyg snarare än som en omdirigeringsteknik.

Extended walking in room-scale VR via a subtle situation-based rotation of the virtual environment while maintaining a full sense of presence

Johannes Karlsson KTH Royal Institute of Technology Stockholm, Sweden [email protected]

may be used as a tool rather than as a redirecting ABSTRACT technique. Assuming that the emergence of inside-out positional tracking in commercially available VR systems indicate a CCS CONCEPTS future where room-scale VR is experienced more freely, • Human-centered computing → Virtual Reality there is a demand for adaptable and immersive VR KEYWORDS locomotion techniques that while enabling real walking Virtual reality, locomotion technique, redirecting overcomes the physical restrictions of a play space without the use of additional hardware. Hence, the purpose of this study was to explore the hypothesis that 1 INTRODUCTION a subtle situation-based rotation of the immersive virtual 1.1 Background environment (IVE) around the user can free up physically restricted virtual space and enable extended Since 2016, commercially available virtual reality (VR) real walking in room-scale VR, while a full sense of systems, such as HTC Vive1 and Oculus Rift2, support real presence is maintained. life motion and interactions to be reLlected in the virtual environment (VE), a new design paradigm named room- Based on Lindings of a literature study, a prototype of an scale VR. By using external sensors, these systems track adaptable and mobile locomotion technique the user (so-called outside-in positional tracking) while manipulating the IVE was developed and tested using who is physically moving around in a designated play three different rotations; a baseline medium rotation, a space and interacting with the VE. As these systems fast and a slow, all deLined through trial and error with require users to clear and dedicate a speciLic area in a the capacities of freeing up restricted virtual space, and room for the setup of static tracking hardware and a of maintaining presence, in mind. The user tests were powerful computer to calibrate the play space, room- designed as a within-subject test, aiming to expose the scale VR has faced criticism3. As of 2019, newer limits in the prototype by putting pressure on two commercial VR systems, such as HTC Cosmos4 and potentially critical factors: user velocity and the capacity Oculus Quest5, track the user through internal sensors, of freeing up restricted virtual space in all directions. so-called inside-out positional tracking. With play space The results imply that the proposed locomotion deLined through the internal sensors upon setup and technique has the potential of extending virtual walking calibration performed entirely by the head-mounted while maintaining a full sense of presence and that there display (HMD), VR can be experienced anytime and is an optimally balanced rotation between the medium anywhere within minutes, hence offering a more mobile and slow rotation used in the present study. However, use. since the participants were not redirected enough to be Immersion is a well-known technological term within VR preserved within the physical play space, the prototype research, and it is in this present study deLined as to which extent a VE can deliver an illusion of the reality to

1 https://www.vive.com/eu/product/#vive%20series 4 https://www.vive.com/us/product/vive-cosmos/features/ 2 https://www.oculus.com/rift/ 5 https://www.oculus.com/quest/ 3 https://www.roadtovr.com/htc-vive-review-room-scale-vr-mesmerising-vr- especially-if-you-have-the-space-steamvr/ the senses of a human user [17]. Immersive VEs (IVE) rotation of the IVE around the user can free up physically strives towards inducing as much presence as possible. restricted virtual space and enable extended real Presence is the subjective perception of immersion, the walking in room-scale VR, while a full sense of presence feeling of “being there” even though you are physically is maintained. not. An important factor is the match between the Due to the lack of similar studies, the following research proprioceptive (a person's ability to determine the question was investigated in an explorative manner: position of their body parts) sensory and visual feedback. Any delay can potentially decrease the level of How to enable extended walking in room-scale VR via a immersion [25]. In room-scale VR, virtually walking by subtle situation-based rotation of the virtual environment really walking is the default way of moving. Real walking while maintaining a full sense of presence? is ideal in the aspect of proprioceptive matching as it involves whole-body movements [14]. However, it 1.3 DelimitaFons leaves a challenge in cases where the IVE is larger than All development was limited to the Oculus Quest. the designated play space [19,29]. However, the discoveries apply to any VR System that uses an inside-out positional tracking system. The research aimed at Linding workarounds for these physical space restrictions has resulted in a plethora of proposed VR locomotion techniques 2 THEORY AND RELATED WORK [24,6,16,5,8,15,2,12,11,30,19,32,10,33,29,9], and several 2.1 Virtual Reality studies comparing these based on various factors [4,31,34,13]. While all controller-based and Virtual Reality (VR) has been used in many contexts and teleportation-based techniques are respectively hence been deLined in a variety of ways. Technologically cognitively [7,13] and perceptually [5] disadvantaged as it has been deLined as “[…] a particular collection of substitutes for natural walking, some motion-based technological hardware, including computers, head- shows promising and compelling results, such as the mounted displays, headphones, and motion-sensing walk-in-place (WIP) locomotion [14,31,34]. However, gloves” [27]. However, for the present study, VR is best since WIP demands additional hardware, the technique deLined as “[…] a medium composed of interactive might not be suited for a future in which commercial VR computer simulations that sense the participants’ is experienced more freely. In terms of resembling position and actions and replace or augment the reality, real walking is ideal, hence proposals within feedback to one or more senses, giving the feeling of redirecting techniques are favorable. While allowing being mentally immersed or present in the simulation (a users to naturally walk within the designated play space, virtual world)” [20]. In simple terms, VR entails exposing these techniques are overcoming the physical our senses to an explorable and interactable immersive restrictions by either manipulation of perceived self- virtual environment (IVE) in such a manner that we motion or manipulations of the spatial qualities of the perceive it as reality. IVE [29,3]. Though, as redirecting techniques often call To enhance the perception of reality, commercial VR for controlled manipulations and particular demands to systems have supported room-scale VR since 2016. the IVE, the Llexibility can be questioned, along with their Room-scale VR entails that physical motion and practical applicability in commercial markets. interactions inside a designated play space in the real world are performed correspondingly in the IVE. The 1.2 Problem statement setup of the VR system depends on its type of positional Assuming that the development and the implementation tracking, though a head-mounted display (HMD) and two of inside-out positional tracking in commercially hand-controllers are usually included. Positional available VR systems indicate a future where room-scale tracking is essential in room-scale VR, as this allows the VR is experienced more freely, there is a demand for VR system to estimate the users’ position relative to the adaptive and immersive VR locomotion techniques that IVE. In commercial VR, this is achieved through either while enabling real walking overcomes the physical outside-in or inside-out positional tracking. restrictions of a play space without the use of additional hardware. The motivation behind this paper is to 2.1.1 Outside-in positional tracking explore the hypothesis that a subtle situation-based

Previously mentioned VR systems HTC Vive and Oculus vividness, and proprioceptive matching [21,25]. These Rift uses outside-in positional tracking, and while both are variables that respectively describe; how effectively depend on stationary placed external hardware, the the physical reality is shut out, how many senses that are tracking technology differs6. Oculus Rift utilizes replaced by the IVE, to which extent the IVE is panoramic “Constellation”, an optical-based technology that tracks and how much of a match there is between the users’ both HMD and controllers using pre-deLined body movements and the visual feedback [25]. If an IVE constellations of infrared LEDs hidden under the effectively substitutes the sensory perceptions with plastics. By processing frames, provided by sensors computer-generated ones, the brain has no alternative connected through USB cables, a PC can recognize but to accept the IVE as reality and consciousness is constellations of IR-LEDs and identify the tracked object. transformed into the virtual scene even though the user Since the PC remembers the previous position of the knows that this is not real [22]. The speciLic feeling of object, it knows its direction and acceleration. The “being there”, in the environment presented by the VR tracking technology utilized by HTC Vive is called displays is referred to in the literature as the sensation of “Lighthouse” and is laser-based. The tracking uses presence, the subjective perception of immersion [22]. stationary placed base stations, or “Lighthouses”, that Presence is usually evaluated through questionnaires continuously alternates between emitting a Llash of IR [23]. light and emitting wide-angle two-dimensional IR laser beams across the room, one axis at a time. Utilizing IR 2.3 LocomoFon in VR photodiodes connected to a chip, each tracked device A fundamental problem in VR research is the determines its position by measuring the time between development of natural substitutes for real physical the Llash and being hit by a laser for each axis. interactions, and the big special case is locomotion through virtual space [4,11]. It is widely believed and by 2.1.2 Inside-out positional tracking research conLirmed, that virtually walking by really Unlike outside-in, inside-out positional tracking depends walking in physical space with a maintained high level of on sensors placed on the tracked device. Oculus Quest proprioceptive matching, strongly affects the presence uses the tracking system Oculus Insight7. By notifying [14,25]. In room-scale VR, this is the default way of unique static features of the physical room, Oculus moving, but it leaves a challenge in scenes where the IVE Insight tracks the HMD by comparing how these appear is larger than the designated play space [19,29]. To with rotations and accelerations provided by a built-in overcome these physical restrictions, research of accelerometer and gyroscope. Similarly, to Constellation, locomotion in VR has proposed a plethora of solutions the handheld devices are tracked constellations of LEDs that can be divided into two different interaction types: and cameras on the HMD. While the play space in artiLicial and physical [3]. outside-in positional tracking is often deLined by the Two techniques that fall under artiLicial interaction are orientation of the external sensors and the interceptions controller-based and teleportation-based locomotion, of their visual ranges, Oculus Insight lets the user deLine with the former being more researched and the latter the play space upon startup of Oculus Quest, by drawing more utilized. Controller-based locomotion artiLicially it in real space by looking through the cameras located moves the user by utilizing some kind of hand controller. on the HMD. However, as it allows for stationary physical use, it can 2.2 Immersion and presence cause cybersickness due to a mismatch between the visual and the proprioceptive and the vestibular senses Immersion and presence are two well-known terms [7,13]. Teleportation-based locomotion is the most within VR research. Immersion is a technological term commercially used technique of all [3]. By instantly that in this present study is deLined by to which extent an teleporting the user to a certain position in the IVE upon IVE can deliver an illusion of the reality to the senses of a pointing at it, the artiLicial movement is non-continuous human user [17]. Immersion is quantitative and essential which, compared to the controller-based locomotion, variables are inclusiveness, extensiveness, surrounding, limits the cognitive pressure to the extent it is less likely

6 https://venturebeat.com/2019/05/05/how-virtual-reality-positional- tracking-works/view-all/ 7 https://uploadvr.com/oculus-insight-details-quest/

to induce cybersickness, even though they are physically real and virtual movements to compress the larger stationary [31]. However, there are reports on users virtual environment into a limited tracking space”[3]. feeling disoriented using this type of locomotion [31]. Research of redirecting techniques can be broadly If considering the amount of reviewed studies, physical divided into two categories; manipulation of perceived interaction is far more explored and applied than self-motion and manipulation of the spatial qualities of artiLicial [3]. This might have its explanation in the vast the IVE [29]. While the latter is relatively new, the former number of proposed motion-based substitutes for has been extensively researched, and proposals can be natural walking that go under this category, with divided into three categories; translation gains, rotation minimal to no risk of being cognitive intense due to the gains, and curvature gains [29]. Translation gain lack of motion instructions. Locomotion techniques that techniques scale the change in tracked head position to continuously move the user, unconstrained by visual enable navigation through IVEs larger than physical play interferences such as “jumps” when teleporting, are also space, e.g. by translating one step in reality into seven in well-preferred over non-continuously ones, as those the IVE [10]. By using translation gain techniques, allow for consistent presence [3]. distances can be downscaled by 14 per cent and upscaled by 26 per cent, without being noticeable [26]. Instead of Walk-in-place (WIP) is the most researched technique tracking the head position, rotation gain techniques within motion-based locomotion [3]. This technique lets track changes in head orientation, and scale the virtual the user explore vast IVEs while physically stationary by rotation to keep the user within physical boundaries. stepping in place and moving in the direction of the gaze Razzaque et al. were able to redirect users into walking [30]. In 1995, Slater et al. developed the Virtual back and forth in physical space while believing they Treadmill, a simple WIP technique that detected steps by zigzagged through a virtual corridor using this technique tracking the HMD using a neural net [24] and found that [19]. Rotation gain techniques can physically turn users naı̈ve users experienced a higher level of presence using 49 per cent more and 20 per cent less than the perceived it, compared to controller-based locomotion [14]. An virtual rotation [26]. While the proposals that fall under almost equally old WIP technique that recently seen an the previous categories are multiplying gains with either upswing in commercial markets8 9 10 11 12, uses an translations or rotations, curvature gain techniques add omnidirectional treadmill to track user movement. offsets to real movements. By doing so, manipulations While this mechanical device lets the user perform are enforced if only one kind of movement is tracked, i.e. physical motion in any direction, there are reports on if the user turns the head while standing still or walks them being hard to enter and exit, limit freedom of straight with Lixed head rotation. Studies show that if the movement, and to cause cybersickness [6]. While several manipulations are small enough, curvature gain can studies comparing different VR locomotion techniques make users walk in a circle with a radius of 22 m or mark WIP as an overall good natural substitute for real greater while believing they are walking on a straight physical walking [14,34], it is impossible to use without line [26]. While it seems that curvature gain techniques additional hardware. require a quite large physical space, studies show that Some proposals that have shown promising and the radius can be signiLicantly decreased by designing compelling results go under the category of redirecting the IVE in a certain way [12] or by adding haptic as techniques. Due to allowing “[…] the user walks freely stimuli in the technique [15]. inside a limited physical space while being able to Redirecting techniques manipulating the spatial explore unlimited virtual environments […][3], they qualities of the IVE is not as extensively researched. A have a perceptual and cognitive advantage towards perceptually promising technique that uses change other techniques of VR locomotion [14,31]. With the blindness illusions managed to reorient the user by ultimate goal to prevent the user from exiting the instantaneously shifting between architectural states, physical play space, “[…] these techniques try to e.g. by Llipping a doorway about its vertical axis [28]. introduce an unnoticeable mismatch between the user’s Though, the technique requires speciLic strict demands

8 https://birdlyvr.com/ 11 https://www.kat-vr.com/ 9 https://www.virtuix.com/ 12 https://infinadeck.com/ 10 https://www.cyberith.com/

to the IVE in order to work. In 2012, Suma et al. proposed for the rotation by redirecting away from the boundary a promising technique called Impossible spaces that while maintaining a full sense of presence. utilizes self-overlapping architecture. By using rooms The situation-based rotation depended on three that are too large to co-exist by Euclidean laws, and variables composed into the following algorithm: switch between them depending on the users’ location, the technique enables the use of IVEs larger than $%&'()%*+ (*',,%(%'+) × -'.*(%)/ ! × physical space. While this technique does not impose any $%0)1+(' )* 2*3+$1&/ 4*%+) predeLined routes or motion, it is advantageous Similar to Razzaque et al. [19], the algorithm employed a compared to many previously mentioned redirecting direction coef?icient and user velocity. The direction techniques. However, the IVE still needs to be designed coefLicient consisted of ( 90 − |1+:.' *, %+(%$'+('| ) in a speciLic way in order to function. in which the angle of incidence is the angle between the forward direction of the HMD and the closest boundary 3 METHOD point. The direction coefLicient was essential to the algorithm as higher rotational speed was required if the 3.1 Literature study user approached the boundary straight forward than if A literature study was conducted in order to map out approaching along the side. However, if the boundary previous research within the subject (see Section 2 for point was on the left side of the user, the rotation was more details), and to investigate the research question performed clockwise, and otherwise anticlockwise. User properly. While real walking is preferable when velocity was necessary as the rotational speed was to be navigating an IVE, proposed locomotion techniques higher if the user approached at a fast pace. Additionally, enabling that, often comes with restrictions, such as distance to boundary point was added to the algorithm as reliance on external hardware or demands on the design a common denominator, since the rotational speed was of the IVE. These contradict a future in which VR is to increase as the user approached. experienced more freely. Nevertheless, redirecting However, while low rotational speed of the IVE is less techniques multiplying gains seem to be able to take on effective in terms of freeing up otherwise restricted an adaptable manner if keeping the sensory mismatch virtual space, high rotational speed may break the unnoticeable. However, while all researched redirecting sensation of presence. In order to Lind the optimal techniques aim to enable unlimited virtual walking, balance, a coefLicient k was added to the algorithm. studies focusing on enabling extended virtual walking Through trial and error, a medium rotation was deLined are non-existing. Hence, with the lack of research, this as a baseline. The same coefLicient also allowed for a slow present study will be conducted exploratory. Inspired by rotation to be deLined at the lower limit of how efLiciently the rotation gain technique proposed by Razzaque. et. al it freed up space, and a fast rotation was deLined at the [19], a prototype of an adaptable and mobile locomotion perceived upper limit of maintained presence. In order technique manipulating the IVE was developed and to Lind an objectively perceived optimal balance, these tested in order to investigate the research question. rotations were used in a user test. 3.2 Prototype 3.3 Recruitment In room-scale VR, consumer VR systems such as Oculus The participants were recruited through social media Quest, guarantee collision-free locomotion by visualizing platforms, such as Facebook and WhatsApp, or by word a grid along the boundary of the play space when the user of mouth, with no speciLic target group in mind. Nor was is approaching. While this grid is hidden by default, the any previous experience in VR required. Though, it was boundary points are yet accessible, and that was desired that the participants did not have any movement essential for this prototype to work. InLluenced by or vision impairments and that they were completely Razzaque et al. [19], the prototype was developed to free unaware of what the present study was about. up otherwise restricted virtual space by performing a subtle situation-based rotation of the IVE with the user 3.4 Study design as a pivot point. By continually locating the boundary The user tests were designed as within-subject tests and point closest to the user and using it to rotate the IVE, the conducted one by one with a supervisor and a aim was to cause the user to unknowingly compensate

participant, and to ensure consistency, they were all The three VR sessions used the same IVE and tasks, but conducted the same way. Due to ethical reasons, each the rotation used in the prototype differed. The medium participant was introduced to the fact that their baseline rotation was always used in the introducing VR participation was entirely voluntary, that they were session, and the permutations of the other two were allowed to discontinue the test at any time, and that their equally divided between the user tests. data is anonymized. After introducing, the participant The IVE was designed as a stripped-down environment signed a form of consent along with some background in order to lower the risk of details affecting the focus of data, such as name, age, gender, and whether or not they the participants, and it consisted of Live scenes, all had experienced VR before. containing identical 5x5 m squared rooms. Except for the Upon Linishing the form, the participant was introduced introducing, each scene had a task, and while the primary to the Oculus Quest and after that instructed to get purpose of the tasks was to distract the user, they acquainted with VR in a pre-test session. Before entering simultaneously urged certain movement in order to the Lirst out of three VR sessions, the participant was let expose the limitations of the prototype. All the tasks know that it was the prototype being tested, not their involved picking up items from the Lloor and putting performance or knowledge of VR. During the VR them in a wooden crate placed close to the users' original sessions, all instructions were provided virtually; hence position. Upon Linishing each task, the user was to push the supervisor only observed their behavior and a red button with the text “Done” written on it. transcribed any vocal expressions. After each VR session, the participant was urged to Lill in the presence questionnaire developed by Witmer et al. [35], while their experience was fresh. This questionnaire is well established in VR research and is used to quantify the level of presence in an IVE. A semi- structured interview was also held with the participant in the break between VR sessions. During this interview, questions like “Did you experience any trouble performing the tasks?” and “How realistic did you experience the virtual environment?” were asked. The Linal two VR sessions were identically conducted as the Lirst. Lastly, the study was explained, and further comments were noted.

3.5 SoOware and hardware All development of the present study utilized the game engine Unity3D13, with Unity XR Plugin14 and native Unity code only. The only necessary hardware was the Oculus Quest that was used as the VR system. Image 3.1: Scene used in Task 1-3 3.6 Environment and tasks The introducing scene was used for educational reasons The physical environment utilized in the user tests was a only, as tests on novel users may affect the results. The 4.5x4.5 m square, located outdoors due to government Lirst, second, and third scenes were identical both in recommendations during ongoing pandemic Covid-19. appearance and task. These scenes had eight The visual grid marking the boundary of the play space, hamburgers randomly scattered on the Lloor, and the remained activated for safety reasons, though adjusted task was to as quickly as possible put Live of them in the to the least sensitive level enabling users to be closer to wooden crate. The reason for repeatedly performing the the boundary without the grid appearing. same task was to statistically eliminate the potential confusion that may come with sudden stress. A

13 https://unity.com/ 14 https://docs.unity3d.com/Manual/XR.html

countdown timer was added to these scenes to 4.2.1 The tasks encourage a competitive spirit. The purpose of these The participants were all able to complete the tasks, scenes was to urge a high-speed movement in order to though all struggled to complete Task 4 at fast rotation. expose user velocity as a limiting factor in the prototype. Some were observed stopping for a while at the The fourth and last scene had a chicken leg placed in each boundary of the play space. Later they said that since the corner of the virtual room, and the task was to put them virtual space rotated out of reach, they had to wait for it all in the wooden crate. The purpose of this last task was to rotate back in order to proceed. One participant to expose limits to the prototypes' capacity of freeing reportedly got stuck in the corner of the physical play restricted virtual space in all directions. space as almost all virtual space had rotated out of range. 3.7 Data Some departing from the instructions occurred. For Both qualitative and quantitative data was gathered example, only one participant realized that the wooden during the user tests. Qualitative data was gathered crate could be picked up and brought with when through semi-structured interviews and by the presence collecting objects. The rest went back and forth, questionnaire [35], and analyzed thematically combined dropping off objects into the wooden crate. This caused with a deductive approach, meaning that the themes that one participant taking a unique route when were predetermined by the hypothesis of this present performing Task 4. Another example is that three study [18] and numerically, respectively. The participants were observed continuing with the high- quantitative data was gathered through logging a few speed movement urged on in Task 1-3 when taking on parameters while the tasks were performed. These Task 4. parameters included time, distance, and velocity. 4.2.2 Medium rotation While all participants expressed conLidence when they at 4 RESULTS a steady pace using large body movements unhindered explored the IVE, a temporary deteriorated conLidence 4.1 ParFcipants was observed in all participants when introduced to the The participants of the present study consisted of eight visual grid marking the boundary of the play space. As people, four females and four males between the ages 24- they quickly backed off, they seemed startled by the 31 years old, with mixed previous experience in VR. All disruption, and they started moving more carefully and participants lived in Stockholm, Sweden. at a slightly slower pace. With these effects lasting a while for some, others appeared startled by the grid each 4.2 ObservaFons and interviews time disrupted by it. Three participants mentioned that the grid reminded them of the real world, and two of these said they did not want to approach it and that they intentionally reduced their pace if they felt that they were close. “I became aware of the outside world as I knew I could not walk through the boundary” (translated) While half of the participants had trouble letting go of the real world, and two of them reported disorientation and nausea, the other half experienced the IVE as natural as reality.

“It felt like I could have started running in there” (translated) 4.2.3 Fast rotation Image 4.1: A participant in action The body language of the participants indicated that they all acted more careful than before.

PRESENCE QUESTIONNAIRE

Medium Fast Slow

4 SCALE

1 PQ 1 PQ 2 PQ 3 PQ 4 PQ 5 PQ 6 PQ 7 PQ 8 PQ 9 PQ 10 PQ 11 PQ 12 PQ 13 ITEMS

Figure 4.2: Box plots displaying the score from the presence questionnaires

“Something felt “off” when I moved quickly” (translated) Average experienced presence Three participants said they were more aware of the real 7 world than before. Another three participants mentioned that the IVE was rotating and one of them 6 reported trouble focusing on the tasks. All but one 5 participant reported either dizziness, disorientation or nausea. 4 5,8 4.2.4 Slow rotation 3 5,5 4,1 Six participants said they did not experience any 2 difference between this VR session and the medium, and 1 Live of these had previously stated that they experienced Medium Fast Slow the IVE using medium rotation as natural as reality. The remaining two said they felt safer and that they were not Figure 4.1: Bar chart displaying the overall score from the as afraid of approaching the boundary of the play space. presence questionnaires “I dared to run” (translated) Figure 4.2 displays the score on each item in the presence

4.3 Presence quesFonnaire questionnaire. The VR session using fast rotation As seen in Figure 4.1, the overall score from the presence resulted in a signiLicantly lower score than the other two questionnaire associated with the fast rotation was in items PQ3, PQ4, PQ6, PQ8, PQ9, and PQ13. Those are signiLicantly lower than the overall scores associated all questions that directly compare the prototype to with the other two. reality in terms of interaction, locomotion, and overall experience.

4.4 Logged data lower when performing Task 4 at fast rotation than at This section contains quantitative data that was logged the other. while the tasks were performed. As Task 1, Task 2, and Task 3 were identical within each VR session; these Medium Fast Slow values are merged and displayed as Task 1-3. 1,4 1,2 Medium Fast Slow 1 120 0,8 100 0,6 80 0,4 VELOCITY (M/S) 60 0,2 0 40 Task 1-3 Task 4 TIME TIME (SECONDS) 20 Figure 4.5: Box plots displaying the velocity for each task in m/s 0 Task 1-3 Task 4

5 DISCUSSION Figure 4.3: Box plots displaying the time of completion for each The purpose of this study was to answer the research task in seconds question by exploring the hypothesis that a subtle situation-based rotation of the IVE around the user can Medium Fast Slow free up physically restricted virtual space and enable extended real walking in room-scale VR, while a full 60 sense of presence is maintained. Based on Lindings of a 50 literature study, a prototype of an adaptable and mobile 40 locomotion technique manipulating the IVE was developed and tested using three different rotations; a 30 baseline medium rotation, a fast and a slow, all deLined 20 through trial and error with the capacities of freeing up restricted virtual space, and of maintaining presence, in 10 DISTANCE (METERS) mind. The results of the user tests are hence discussed 0 from the perspective of each of these capacities. Task 1-3 Task 4

5.1 Freeing up virtual space Figure 4.4: Box plots displaying the travelled distance for each Since the virtual space was larger than the physical play task in metres space and that all participants were able to pick up the As seen in Figures 4.3 and 4.4, respectively, the Ligures chicken legs in Task 4, the prototype was successful in shape a pattern regarding time to complete, and terms of freeing up physically restricted virtual space. distance traveled. While Task 1-3 is performed The logged data of Task 1-3 also indicates that user somewhat equally regardless of rotation, Task 4 could velocity had minor to no effect on the prototype, meaning be signiLicantly more consumable in both time and that quick movements are not a limiting factor in terms distance at fast rotation. Figure 4.5 displays that it was of freeing up virtual space. the velocity used performing Task 1-3 was similar However, the compiled data of Task 4 suggests that the between the rotations. However, the compactness of the prototype may be limited in freeing up virtual space in all boxes gives medium rotation the smallest spread and directions. While the participants required signiLicantly the fast rotation the most signiLicant spread. more time and distance completing Task 4 at fast Furthermore, the participants’ velocity was signiLicantly rotation compared to the other, they also navigated at a

slower pace. This data is undoubtedly affected by the fact the participants could have been redirected more by that one participant reported got stuck in the corner of higher rotational speed, the fact that the IVE reportedly the physical play space with almost all virtual space rotated out of reach at fast rotation proves a fundamental rotated out of reach. Though, as several participants problem with the prototype. A solution for this could be were observed stopping at the boundary of the play to place the pivot point for the rotation closer to the space and later the same participants reported that they center of the IVE. However, as fast rotation scored had to wait for the virtual space to rotate back within signiLicantly lower on the presence questionnaire than reach in order to proceed, the directional range appears the other rotations, a higher rotational speed could be to be a limiting factor in the prototype. While it is difLicult devastating immersion wise. Assuming that the test to pinpoint this limit without further research, the environment potentially affected the redirecting ability, compiled data indicates the prototype being successful the play space should perhaps have been drawn regarding directional range at the other rotations. As the circularly. Since the rotation depended on the closest logged data indicate that Task 4 was performed almost boundary point, corners may have caused trouble. While equal regardless of medium or slow rotation, the a thoroughly conducted research investigating the medium rotation should be preferred as a faster rotation redirecting contribution of each component of the is more effective in freeing up virtual space. rotation formula may improve the ability to redirect the user away from the boundary while causing the user to 5.2 Eﬀects on presence unknowingly compensate for the rotation, it is The results from the presence questionnaires imply that unreasonable to believe it will fully work. As curvature the experienced subjective presence, the sensation of gain can cause users to walk in a circle with a radius of “being there” in a virtually presented environment [22], 22 m or greater while believing they are walking on a varied between the rotations. While the overall score straight line [26], additional rotations must be included describing the average experienced presence in Figure in order to preserve the user within a smaller play space. 4.1 is just slightly higher at slow rotation than medium, For example, add a situation-based rotational gain on the the score associated with fast rotation is signiLicantly substantial vestibular stimulation caused when rapidly lower. These results are in line with the qualitative data turning our head [19]. acquired through the observations and interviews. As the body language of the participants was observed 5.4 The opFmal rotaFon expressing less conLidence at fast rotation, the With the medium rotation being advantageous to slow in behavioral presence, which is the observable response to terms of freeing up virtual space, it is unclear whether stimuli [25], this further implies that fast rotation was the small difference in presence is crucial. Depending on not as immersive as medium and slow. Furthermore, as desired abilities, the results indicate that with the all but one participant experienced adverse effects on prototype as it is, there is an optimally balanced rotation their well-being, fast rotation potentially caused a between the medium and slow rotation used in the noticeable mismatch between the proprioceptive present study. Regardless of the choice of rotation sensory and the visual feedback [1]. The slight difference between these, the prototype seems to enable quick in presence between slow and medium rotation is also movement and while not being limited by directional present in the data derived from the interviews as Live range. However, since the participants were continually participants stated that they experienced both rotations disrupted by the boundary, they were not redirected as natural as reality, but another two said they felt safer enough to be preserved within the physical play space. at slow rotation. Hence, suggesting this prototype may be used as a tool rather than as a redirecting technique. 5.3 RedirecFng ability Unfortunately, there is still a lot to ask for in the 5.5 Method criFcism redirecting ability of the prototype, at least if the user is 5.5.1 Covid-19 to unknowingly compensate for the rotation. Since the Due to government recommendations following ongoing participants, regardless of rotation, were continually pandemic Covid-19, the present study was limited in disrupted by the grid marking the boundary of the play terms of participants. Even though the user test was space, they were not redirected enough. Assuming that adapted according to ofLicial safety measures, destined

participants chose to be careful and not participate, and 6 CONCLUSION due to the time frame of the study, waiting out the The research question for this present study was: pandemic was not an option. Therefore, the statistical reliability of the conclusions of this study can be How to enable extended walking in room-scale VR via a questioned. subtle situation-based rotation of the virtual environment while maintaining a full sense of presence? 5.5.2 Test design A prototype of an adaptable and mobile locomotion As the baseline medium rotation was used Lirst in each technique manipulating the IVE was developed and user test and that the order of the other two rotations tested using three different rotations; a baseline medium was randomized, there is reason to question the rotation, a fast and a slow, all deLined through trial and objectivity of this study. The order of all rotations should error with the capacities of freeing up restricted virtual have been randomized, with each permutation of the space, and of maintaining presence, in mind. The user three being equally utilized. For the same reasons, no tests were designed as a within-subject test, aiming to rotation should have been applied to the introducing expose the limits in the prototype by putting pressure on scene in which the users were to be acquainted with the two potentially critical factors: user velocity and the VR-system. capacity of freeing up restricted virtual space in all 5.5.3 The visual grid marking the boundary directions. The results imply that the proposed locomotion technique has the potential of extending Since the visual grid that marks the boundary of the play virtual walking while maintaining a full sense of area remained activated for security reasons during the presence and that there is an optimally balanced rotation user tests, it likely affected the sense of presence. between the medium and slow rotation used in the Although hidden by default, it becomes visible when present study. However, since the participants were not approaching it. As it does, it brings a hint of reality by redirected enough to be preserved within the physical indicating the users' physical position. Furthermore, as play space, the prototype may be used as a tool rather this grid is static, a rotational IVE becomes very than as a redirecting technique. Nevertheless, more noticeable. research needs to be conducted. 5.5.4 Logged data The logged data could have been expanded. As it is likely ACKNOWLEDGEMENTS that the distance parameter was affected by the rotation, There are some very special people whom I would like to a parameter logging the amount of rotation could have acknowledge. Without these people, this thesis would improved the analysis of the user tests. not have become what it is. Firstly, a big thank you to Björn Thuresson for being an amazing supervisor.

5.6 Future work Secondly, I wish to thank my parents for supporting me, Since this present study was conducted in an exploratory both in terms of being respectful and motivating, but also manner, future research can be conducted in several for offering accommodation and babysitting during the Lields in order to improve the prototype as a whole or any most stressful of times. Finally, I wish to give my biggest of its components. With the results indicating the thanks to my wonderful girlfriend Hedvig Fahlstedt and existence of a rotation balancing the capacities of my loving daughter Louie, whom I would not be sitting maintaining presence and of freeing up restricted virtual here without. space, an essential suggestion would be a thoroughly performed study deLining it. Another suggestion would be to break down the formula used in the prototype and REFERENCES investigate the role of each component in terms of 1. Balk SA, Bertola MA, Inman VW. Simulator rotating an IVE while maintaining a full sense of Sickness Questionnaire: Twenty Years Later. presence. Furthermore, future research could 2013;257–63. investigate how this technology could be improved to be 2. Bhandari J, Tregillus S, Folmer E. Legomotion: used as a tool, rather than as a redirecting technique. Scalable walking-based virtual locomotion. Proc ACM Symp Virtual Real Softw Technol VRST.

2017;Part F1319. Influence of a Walking Technique on Presence in Virtual Reality. ACM Trans Comput Interact. 3. Boletsis C. The new era of virtual reality 1995;2(3):201–19. locomotion: A systematic literature review of techniques and a proposed typology. Multimodal 15. Matsumoto K, Ban Y, Narumi T, Yanase Y, Technol Interact. 2017;1(4):1–17. Tanikawa T, Hirose M. Unlimited corridor: Redirected walking techniques using visuo 4. Bowman DA, Koller D, Hodges LF. Travel in haptic interaction. ACM SIGGRAPH 2016 Emerg immersive virtual environments: an evaluation Technol SIGGRAPH 2016. 2016;16–7. of viewpoint motion control techniques. Proc - Virtual Real Annu Int Symp. 1997;45–52. 16. McCullough M, Xu H, Michelson J, Jackoski M, Pease W, Cobb W, et al. Myo arm-swinging to 5. Bozgeyikli E, Raij A, Katkoori S, Dubey R. Point & explore a VE. Proc - SAP 2015 ACM SIGGRAPH Teleport locomotion technique for virtual reality. Symp Appl Percept. 2015;107–13. CHI Play 2016 - Proc 2016 Annu Symp Comput Interact Play. 2016;205–16. 17. Mestre D, Vercher J-L. Immersion and presence. Virtual Real. 2011; 6. Darken RP, Cockayne WR. The Omni-Directional Treadmill: A Locomotion Device for Virtual 18. Pope C, Ziebland S, Mays N. Analysing qualitative Worlds. UIST ’97 Proc 10th Annu ACM Symp User data. Br Med J. 2000;320(7227):114–6. interface Softw Technol. 1997;213–21. 19. Razzaque S, Kohn Z, Whitton MC. Redirected 7. Fernandes AS, Feiner SK. Combating VR sickness Walking. Proc EUROGRAPHICS. 2001;289–94. through subtle dynamic field-of-view 20. Sherman WR, Craig AB. Understanding Virtual modification. 2016 IEEE Symp 3D User Reality: Interface, Application, and Design. Interfaces, 3DUI 2016 - Proc. 2016;201–10. Understanding Virtual Reality: Interface, 8. Ferracani A, Pezzatini D, Bianchini J, Biscini G, Del Application, and Design. Morgan Kaufmann Bimbo A. Locomotion by natural gestures for Publishers; 2003. 1–580 p. immersive virtual environments. AltMM 2016 - 21. Slater M. A Note on Presence Terminology. Proc 1st Int Work Multimed Altern Realities, co- Emotion. :1–5. located with ACM Multimed 2016. 2016;21–4. 22. Slater M, Sanchez-Vives M V. Enhancing our lives 9. Harris A, Nguyen K, Wilson PT, Jackoski M, with immersive virtual reality. Front Robot AI. Williams B. Human joystick: Wii-leaning to 2016;3(DEC):1–47. translate in large virtual environments. Proc - VRCAI 2014 13th ACM SIGGRAPH Int Conf 23. Slater M, Steed A, McCarthy J, Maringelli F. The Virtual-Reality Contin Its Appl Ind. 2014;231–4. Influence of Body Movement on Subjective Presence in Virtual Environments. Hum Factors J 10. Interrante V, Ries B, Anderson L. Seven league Hum Factors Ergon Soc. 1998;40(3):469–77. boots: A new metaphor for augmented locomotion through moderately large scale 24. Slater M, Steed A, Usoh M. The Virtual Treadmill: immersive virtual environments. IEEE Symp 3D A Naturalistic Metaphor for Navigation in User Interfaces 2007 - Proceedings, 3DUI 2007. Immersive Virtual Environments. Virtual 2007;167–70. Environ ’95 Sel Pap Eurographics Work Barcelona, Spain, 1993 Monte Carlo, Monaco, 11. Iwata H. Walking about virtual environments on 1995. 1995;135–48. an infinite floor. Proc - Virtual Real Annu Int Symp. 1999;286–93. 25. Slater M, Wilbur S. A Framework for Immersive Virtual Environments (FIVE): Speculations on the 12. Langbehn E, Lubos P, Bruder G, Steinicke F. Role of Presence in Virtual Environments Mel. Application of redirected walking in room-scale Presence Teleoperators Virtual Environ. 1997; VR. Proc - IEEE Virtual Real. 2017;2:449–50. 26. Steinicke F, Bruder G, Jerald J, Frenz H, Lappe M. 13. Langbehn E, Lubos P, Steinicke F. Evaluation of Estimation of Detection Thresholds for locomotion techniques for room-scale VR: Redirected Walking Techniques. 2010;16(1):17– Joystick, teleportation, and redirected walking. 27. ACM Int Conf Proceeding Ser. 2018; 27. Steuer J. Defining Virtual Reality: Dimensions 14. Martin Usoh MS, Steed A. Taking Steps: The

Determining Telepresence. J Commun. 1992;42(4):73–93.

28. Suma EA, Clark S, Krum D, Finkelstein S, Bolas M, Warte Z. Leveraging change blindness for redirection in virtual environments. Proc - IEEE Virtual Real. 2011;159–66.

29. Suma EA, Lipps Z, Finkelstein S, Krum DM, Bolas M. Impossible spaces: Maximizing natural walking in virtual environments with self- overlapping architecture. IEEE Trans Vis Comput Graph. 2012;18(4):555–64. 30. Templeman JN, Denbrook PS, Sibert LE. Virtual Locomotion: Walking in Place through Virtual Environments. 1999;8(6):598–617. 31. Usoh M, Arthur K, Whitton MC, Bastos R, Steed A, Slater M, et al. Walking > Walking-in-Place > Flying , in Virtual Environments. 1999;359–64. 32. Williams B, Narasimham G, McNamara TP, Carr TH, Rieser JJ, Bodenheimer B. Updating orientation in large virtual environments using scaled translational gain. Proc - APGV 2006 Symp Appl Percept Graph Vis. 2006;1(212):21–8. 33. Williams B, Narasimham G, Rump B, McNamara TP, Carr TH, Rieser J, et al. Exploring large virtual environments with an HMD when physical space is limited. ACM Int Conf Proceeding Ser. 2007;253(212):41–8. 34. Wilson PT, Kalescky W, Maclaughlin A. VR Locomotion : Walking > Walking in Place > Arm Swinging. 2015;243–9. 35. Witmer BG, Singer MJ. Measuring Presence in Virtual Environments: A Presence Questionnaire. 2008;(1996):225–40.

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