Balance Exercises for Seniors in Virtual Reality
Markéta Machová
Supervisor: Ing. David Sedláček, Ph.D.
May 2021
Department of Computer Science Faculty of Electrical Engineering Czech Technical University in Prague
I. OSOBNÍ A STUDIJNÍ ÚDAJE
486986 Osobní číslo:
Markéta Jméno:
Machová Příjmení:
Fakulta elektrotechnická Fakulta/ústav:
Zadávající katedra/ústav: Katedra počítačů
Softwarové inženýrství a technologie Studijní program:
II. ÚDAJE K BAKALÁŘSKÉ PRÁCI
Název bakalářské práce:
Balanční cvičení pro seniory ve VR Název bakalářské práce anglicky:
Balance exercises for seniors in VR
Pokyny pro vypracování:
1) Analyzujte požadavky na VR zážitek spojený s cestováním krajinou pro testování stability uživatele na zařízení zvaném posturomed.
2) Navrhněte 3 různé VR světy pro virtuální procházky o délce cca 5 minut dle požadavků z bodu 1. Dále navrhněte kontrolní aplikaci informující školený personál o postupu uživatele s možností kontroly zobrazovaného VR obsahu (výběr procházky, start, ukončení, zkrácení).
3) Obě navržené aplikace (VR a mobilní app) implementujte.
4) Otestujte s pověřenou osobou z domova pro seniory - Nová Slunečnice.
Seznam doporučené literatury:
1] Jason Jerald. 2015. The VR Book: Human-Centered Design for Virtual Reality. Association for Computing Machinery and Morgan & Claypool, New York, NY, USA.
2] Steven M. LaValle - Virtual Reality, Cambridge University Press 2016
Jméno a pracoviště vedoucí(ho) bakalářské práce:
Ing. David Sedláček, Ph.D., katedra počítačové grafiky a interakce FEL Jméno a pracoviště druhé(ho) vedoucí(ho) nebo konzultanta(ky) bakalářské práce:
Termín odevzdání bakalářské práce: 21.05.2021 Datum zadání bakalářské práce: 11.02.2021
Platnost zadání bakalářské práce: 30.09.2022
___________________________
___________________________
___________________________
prof. Mgr. Petr Páta, Ph.D.
podpis děkana(ky) podpis vedoucí(ho) ústavu/katedry
Ing. David Sedláček, Ph.D.
podpis vedoucí(ho) práce
III. PŘEVZETÍ ZADÁNÍ
Studentka bere na vědomí, že je povinna vypracovat bakalářskou práci samostatně, bez cizí pomoci, s výjimkou poskytnutých konzultací.
Seznam použité literatury, jiných pramenů a jmen konzultantů je třeba uvést v bakalářské práci.
.
Datum převzetí zadání Podpis studentky
This thesis aims to create a virtual reality application usable for balance training for older adults along with a mobile application for controlling the VR experience. The VR application mediates an experience of travelling through a landscape. The text analyses the theory regarding postural stability, motion sickness, and VR design guidelines. It de- scribes the process of design and implementation and outlines the used testing methods and their results for both applications.
Keywords:virtual reality, VR, stability, motion sickness, balance training, Posturomed
Tato práce si klade za cíl vytvořit aplikaci pro virtuální realitu použitelnou pro trénink rovnováhy pro seniory a mobilní aplikaci pro ovládání virtuálního zážitku. Aplikace pro virtuální realitu zprostředkovává zážitek cestování krajinou. Text analyzuje teorii týka- jící se posturální stability, kinetózy a osvědčených postupůpro návrh aplikací ve virtu- ální realitě. Popisuje proces návrhu a implementace a nastiňuje použité testovací metody pro oběaplikace spolu s jejich výsledky.
Klíčová slova:virtuální realita, VR, stabilita, kinetóza, balanční cvičení, Posturomed
I declare that the presented work was developed independently and that I have listed all sources of information used within it in accordance with the methodical instructions for observing the ethical principles in the preparation of university theses.
Prague, date ... ...
signature
I would like to thank my supervisor Ing. David Sedláček, Ph.D. for his guidance and valuable advices during the development of the bachelor thesis.
Introduction 1
1 Background 3
1.1 Virtual Reality . . . 3
1.2 General VR Design Guidelines . . . 3
1.2.1 Intuitive Interactions . . . 3
1.2.2 Experience Intensity . . . 4
1.2.3 Uncanny Valley . . . 4
1.2.4 User’s Body . . . 5
1.2.5 The Illusion of Physical Interaction . . . 5
1.2.6 Design for Emotions . . . 5
1.2.7 Create Personas . . . 6
1.2.8 Testing . . . 6
1.3 Motion Sickness . . . 6
1.3.1 Origin Theories . . . 6
1.3.2 Acceleration . . . 8
1.3.3 Measuring . . . 8
1.4 Locomotion . . . 9
1.4.1 Locomotion Techniques . . . 10
1.4.2 Locomotion Design Guidelines . . . 11
1.5 Latency . . . 13
1.6 Frame Rate and Refresh Rate . . . 14
2 Postural Stability 15 2.1 Posture . . . 15
2.2 Falls and Their Prevention . . . 15
2.3 Posturomed . . . 16
3 Design 17 3.1 System Background and Usage . . . 17
3.1.1 Target User Group . . . 18
3.1.2 User Roles . . . 18
3.2 System Architecture . . . 19
3.3 Software Requirements . . . 19
3.3.1 Functional Requirements . . . 19
3.3.2 Non-functional Requirements . . . 25
3.4 Prototyping . . . 28
3.5 Existing Solutions . . . 28
3.5.1 Epic Roller Coasters . . . 29
4.1.1 Unity . . . 31
4.1.2 Autodesk Maya . . . 31
4.1.3 Substance Painter . . . 31
4.1.4 Figma . . . 32
4.1.5 Unity Packages . . . 32
4.2 VR application . . . 33
4.2.1 Means of Transport . . . 33
4.2.2 Locomotion . . . 34
4.2.3 Scene . . . 35
4.2.4 Virtual Representation of Hands . . . 37
4.2.5 Calibration . . . 37
4.2.6 Optimisation . . . 39
4.3 Control Application . . . 41
4.3.1 Networking . . . 42
4.3.2 User Interface . . . 43
4.3.3 Localisation . . . 45
4.4 Challenges . . . 45
5 Testing 47 5.1 VR Application . . . 47
5.1.1 Performance . . . 47
5.1.2 User Testing . . . 47
5.2 Control Application . . . 50
5.2.1 Availability . . . 50
5.2.2 User Testing . . . 50
Conclusion 53 References 55 A Health Effects Questionnaire 63 B Installation Manual 65 B.1 Git Project Cloning . . . 65
B.1.1 Required Software . . . 65
B.1.2 Installation . . . 65
B.2 VR Application . . . 65
B.2.1 Required Hardware . . . 65
B.2.2 Required Software . . . 65
B.2.3 Installation . . . 66
B.3 Control Application . . . 66
B.3.1 Required Hardware . . . 66
B.3.2 Required Software . . . 66
B.3.3 Installation . . . 66
B.4 Unity Project Installation . . . 67
B.4.1 Required Software . . . 67
B.4.2 Installation . . . 67
Virtual reality (VR) is gradually maturing into a conventional piece of technology. With the arrival of mobile VR head-mounted displays, virtual reality progressively becomes more affordable and, therefore, more widespread in the commercial sphere. VR usage options vary, and its new use cases keep on arising. Entertainment, education, fitness, science, productivity, medicine, and expert training are all fields virtual reality is not only usable but also has the potential to excel in.
Balance training helps maintain postural stability, reduces reaction time for unex- pected events, and represents one of the numerous effective programs for fall prevention.
The main goal of this thesis is to create an application for virtual reality that serves as an auxiliary tool for proprioceptive exercises for seniors. The application is intended to be used in Nová Slunečnice retirement home, whose medical faculty decided to enhance the everyday exercises with virtual reality.
Incorporating stability exercises with virtual reality and older adults may seem sur- prising at first glance. The main idea of the application is to benefit from the sense of presence, which virtual reality facilitates.
Science fiction books and films often portray a prediction of virtual reality being a technology of immense possibilities. The inventor of the first virtual reality headset I. Sutherland [24] prognosticated his vision of the future appearance of virtual reality:
"The ultimate display would, of course, be a room within which the computer can control the existence of matter. A chair displayed in such a room would be good enough to sit in.
Handcuffs displayed in such a room would be confining, and a bullet displayed in such a room would be fatal."
For the purpose of this thesis, although, a convincing visual perception of motion is sufficient. When a person perceives themselves moving, they perform automatic body movements. These movements can sometimes be barely noticeable but play a significant role in the ability to stand or sit in a stable way. For instance, observing self-motion in a forward-rising direction, one slightly leans forward. These movements can be taken ad- vantage of on a balance platform, where one trains their stability once these movements occur.
The implemented application is intended to be used in a way that a user is wearing a VR head-mounted display, being immersed in a VR experience, while standing on a balance platform. This thesis also involves the development of a mobile application used by a physiotherapist to control the VR application during the exercises. The VR application is intended to be used on the Oculus Quest device, and the mobile application is developed for an Android device.
Structure
Chapter 1gives an introduction to topics of virtual reality. It presents design guidelines for the development of VR applications, examines the problematics of motion sickness, and analyses design guidelines to prevent motion sickness. It provides examples of com- mon techniques used for movement in VR.
InChapter 2, fundamental terms regarding postural stability and the Posturomed bal- ance platform are presented.
Chapter 3presents the functionalities of the applications and collates them into require- ments. Moreover, it defines the target user group and analyses an existing application with similar characteristics.
Chapter 4presents the technology stack, outlines the implementation process, and de- scribes the motivation between certain implementation approaches. Also, it presents a few challenges that have occurred during implementation.
Chapter 5presents the methods used for testing along with the gathered results.
Background
1.1 Virtual Reality
Virtual reality can be defined as: "an artificial environment which is experienced through sensory stimuli (such as sights and sounds) provided by a computer and in which one’s actions partially determine what happens in the environment"[15].
VR experiences can create a perfect illusion of being in a different place or even a world.
Thus, VR is immensely suitable for video games and immersive films. However, its po- tential far exceeds the entertainment industry. VR can be utilised in various domains.
With the capabilities of visualising abstract topics and simulating reality, VR can be utilised in various domains, from education to expert training, to architecture, to fitness.
Augmented reality (AR) is a term similar to virtual reality. Augmented reality, as opposed to virtual reality, does not intend to replace the real world with a virtual one, but rather adds virtual objects to the real world [8]. AR is commonly realised with smartphone cameras, in a way that the real world visible through a device is overlayed with digital information [15].
1.2 General VR Design Guidelines
In comparison with traditional media, VR experiences can multiply evoked emotions, including the pleasant, and the negative ones. For instance, uncanny content can become terrifying when one is seemingly present in the situation, or annoyance can become frus- tration when the experience is defective. On top of that, VR can induce medical side effects, as discussed in Section 1.3.
With that said, as enjoyable as VR experiences can be, they can have serious draw- backs when designed poorly. Since a user wearing a head-mounted display and all he sees is content of the VR application, a VR designer should strive to make the experience usable, comfortable, as well as keep the experience immersive to preserve the illusion.
This chapter collates best-practices for VR application design in terms of user expe- rience.
1.2.1 Intuitive Interactions
Intuitiveness is undoubtedly an essential quality every software product should have.
J. Jerald [8] defines intuitiveness as a trait of ease of use, understandability and pre- dictability.
A user is likely to find a VR interaction intuitive if they can find similarities with the interactions of other VR experiences he had experienced. Therefore, a developer should use standard button mapping for the device, the application is developed for [13]. Also, the default button mapping for the VR platform is usually supported by thorough user testing.
A convenient alternative to using VR controllers for interaction with virtual objects is using own hands for that purpose. The hand-tracking interaction technique is very intuitive, but is not yet fully standardised and can contain errors.
A VR developer should also acknowledge the fact that a user might be right or left- handed. Hence, the application should allow interaction with either hand [13].
Interaction should not be gazed based, controller input based variants should be cho- sen instead, as long as it complies with the application theme [13]. The reason for that is one might not have the intention to trigger a special action, as he might be just staring at one place for no reason.
1.2.2 Experience Intensity
VR experiences can be immersive to such extent, that a user might not be comfortable with. The discomfort rate may be multiplied for intense VR content. Hence, it is impor- tant to inform users in advance about explicit or in any way, intensive content [13].
Besides, VR experience should open into a calmer ambience together with gradually introducing users into intense experiences, so that they better accustom to the content of the application [13].
1.2.3 Uncanny Valley
M. Mori [18] states that our sympathy for human-like looking robots is not increasing linearly as the robot’s human likeness increases. In fact, the sympathy for human-like looking robot goes steeply down as the robot’s human likeness reaches a certain point.
Figure 1.1:Diagram shows the relation between a robot’s human likeness and a person’s sympa- thy for the robot [18]
.
The Uncanny valley phenomenon does not apply only for robots, any human-like character resembling human almost, but not yet perfectly can be found creepy for a per- son [8].
When designing for a VR experience, a designer should avoid creating characters resembling human too much and instead aim for simplicity or stylisation. This can be generalised for a VR experience scene design, as the goal of VR is not a photorealistic replication of reality. A VR experience immersiveness does not necessarily correlate with photo-realism, but rather with other aspects, such as responsiveness of the application or the illusion of physical interaction [8].
1.2.4 User’s Body
Although seeing our bodies looking down every day is an inseparable part of the real-life experience, for VR, it is not a necessary trait. A user, in fact, can feel present in the VR experience even if they do not see their own body [8].
However, displaying the user’s virtual body can add to the illusion of presence. Per- haps surprisingly, the user can feel comfortable even seeing a virtual body that does not quite look like his own real one. For instance, different skin color may not be much of a problem. This is likely to be possible, thanks to our habit of changing clothes daily [8].
Even though a user can be quite tolerant in terms of his virtual body looks, the motion of the body is significant, seeing that the virtual body moves should, to some extent, match the moves of the user’s own body [8].
Also, a developer should be cautious, regarding the virtual body and its motion, as quirky moves can add to the uncanny valley effect, as mentioned in Section 1.2.3 [18].
1.2.5 The Illusion of Physical Interaction
A user should physically feel a response to his interaction with virtual objects. This can be achieved either using real-world objects as a physical embodiment of the virtual ones or, more commonly, haptics controlled by computer resulting in vibrating feedback in VR controllers [8].
If haptics is not available, another form of feedback should be used - e.g., sounds or visually highlighting interacted objects. Note that too much feedback can be overwhelm- ing for the user [8].
The illusion of physical interaction is yet vanishing when VR controllers are used for manipulating weighty objects. In most cases, VR controllers cannot simulate the resis- tance physically felt when operating with heavier real-world objects. Therefore, a de- signer is recommended to either find ways to make up for the lack of physical resistance or not to use weighty objects interaction [13].
1.2.6 Design for Emotions
Emphasis on Introduction and Conclusion
In many cases, the introduction and conclusion of any artistic experience, e.g., a play or film are the parts, that make the biggest impression on us, either positive or negative.
According to [8], the same applies for a VR experience, as the whole experience can be ruined by poor initiation, or conversely elevated by a virtuous ending (and vice versa).
J. Jerald [8] proposes to design the end of a VR experience, such that it evokes positive emotions, as the end is likely to be remembered by the users.
Evoke memories
In general, evoking memories is a powerful method for inducing emotions in a person. A VR designer can embed objects in a scene that a user might know from past and therefore evoke memories [8].
1.2.7 Create Personas
A persona is a well-used technique for modelling an end-user in user experience design.
It helps a designer understand the end-user by defining the user’s personality, needs, motivation and struggles [6].
By creating personas, a VR designer can define typical end-users of the designed VR experience, shape their motivations and needs and pinpoint their struggles. This can be later useful for adjusting the experience so that it best fits the modelled end-user [8].
1.2.8 Testing
Discomfort and sickness, as discussed in Section 1.3, often fade away with experienced VR users [13]. A VR developer should always keep in mind that if the experience suits him, it might not be necessarily true for a novice VR user [8]. Thus, frequently testing the application with unexperienced VR users is crucial.
Additionally, defining the end-users of the application and study their characteristics with personas, as mentioned in Section 1.2.7, and thereafter testing the application with users reasonably similar to the personas can also be very beneficial [8].
1.3 Motion Sickness
Motion sickness can be defined as a sickness induced by motion, such as in a car, plane, or boat and characterised by nausea [15]. J. Jerald extends this definition such that the motion is not necessarily only being induced by travelling in a vehicle (referred to as physical), but also visual, which can be induced by VR usage [8].
Motion sickness resulting from visual motion is induced by visual perception of mo- tion and therefore can be stopped by closing one’s eyes. That does not apply for sickness caused by physical motion [8].
The frequent symptoms of motion sickness include nausea, dizziness or headache. In sparse cases, motion sickness can lead to vomiting [14]. Motion sickness is an unpleasant condition that can ruin any VR experience regardless of the rate of immersiveness, the quality of graphics or the liveliness of storytelling. Therefore, it is important for a VR de- veloper to understand the background of motion sickness and be aware of the situations in which it can be induced.
This section intends to explain the possible causes of motion sickness, as well as how motion sickness originates evolutionarily. Moreover, this section describes the means of measuring and testing motion sickness. As the motion sickness is broadly experienced among VR users, it is not by far the only health impact a VR experience can have. It finally presents other common adverse health effects.
1.3.1 Origin Theories
In spite of the fact, that motion sickness is a frequent ailment, whose occurrence is not limited to VR, the biological processes that human body undergoes prior to experiencing
motion sickness symptoms are not yet well understood. Nevertheless, the motion sick- ness is considered to be evolved genetically [14]. The theories described below explain how motion sickness possibly originates.
Sensory Conflict Theory
Sensory conflict theory asserts that there is a mismatch between what is perceived by our sensory systems. The sensory conflict results in motion sickness [8]. Commonly, the involved systems are the visual system (eyes) and the vestibular system. The vestibular system is located in the inner ear and serves for maintaining balance, coordination, as well as awareness of spatial orientation. The key part of the vestibular system determin- ing the induction of motion sickness is the otolith organs. The otolith organs can detect acceleration [4, 5].
Suppose reading a book while travelling in a car. One’s eyes perceive no motion, as one is focusing own vision on the book. The vestibular system, on the other hand, recog- nises physical motion, as one is moving along with the car. This resulting conflict be- tween two sensors is what causes motion sickness [8]. Motion sickness can be suppressed by looking through a car window, as the vision recognises motion and the conflict no longer exists.
In VR, the sensory conflict usually originates the other way around. When navigating through a virtual scene, a user perceives motion visually, but the vestibular system senses no motion. The conflict between sensors results in motion sickness. As mentioned before, this kind of motion sickness induced by visual sensing of motion can be stopped simply by closing the eyes [8]. However, this is not a permanent solution, and other precautions could be made to prevent motion sickness in VR.
Evolutionary Theory
Evolutionary theory suggests that the possible reason behind a sensory conflict resulting in motion sickness is an evolutionary adaptation for ingesting toxins. Since some toxins can cause malfunction of vestibular, as well as sensory systems, the conflict of sensors could be interpreted by the brain as an effect of poisoning. Therefore, the motion sickness symptoms such as nausea, sweating and vomiting would be the body’s attempts to get rid of ingested toxins [28].
Rest Frame Theory
Rest Frame Theory states that some, but not all sensory conflicts result in motion sick- ness. Instead, if a part of the scene that was perceived as stationary - rest frame, turned out not stationary and started moving, then this conflict between the perception of rest frames and the vestibular system would cause motion sickness [8].
For example, when a user is virtually moving in a VR experience, the virtual ground is moving beneath the user. Since the ground is considered as a rest frame and therefore should not move, then the user must be moving. However, the vestibular system per- ceives no movement of the user, so a sensory conflict occurs and motion sickness results [8].
A VR designer should therefore focus on parts of the scene that are usually perceived as stationary, such as background, and keep those, at least partially, stationary [8].
This theory also is in accord with the fact that augmented reality is less prone to motion sickness than entirely virtual reality. The reason for it is that the real world can be seen apart from virtual objects, which can be perceived as a rest frame [8].
1.3.2 Acceleration
In terms of visual motion, motion sickness does not result from apparent moving at a constant velocity. Instead, acceleration is what causes motion sickness [8]. The reason behind it is that the otolith organs that are part of our vestibular system can, in fact, detect acceleration, not velocity. Acceleration is a rate of change of velocity. For example, speeding up, slowing down, and even changing direction is acceleration [7].
1.3.3 Measuring
Since the motion sickness can result in multiple different symptoms with one person which on top of that vary from person to person, the techniques for measuring motion sickness are not straightforward. In addition, the symptoms of a user having a milder course of motion sickness can fade away quickly after the exposure to visually induced motion. Another issue obstructing objective measuring of motion sickness is the fact that users can adapt to alleviate motion sickness over time [8].
This section discusses the recommended means of collecting data and measuring mo- tion sickness. These techniques can also be generalised for measuring most forms of VR sickness [8].
Questionnaire
A commonly used technique for collecting data from a broad range of users is a question- naire. The main advantage of using a questionnaire is that it can reach a large number of respondents and collect answers effectively. However, a researcher must keep in mind to pose relevant questions and choose the wording well, in order to obtain information that is applicable.
Another disadvantage of using a questionnaire or any self-evaluation method, in gen- eral, is that a respondent’s answers are subjective [8]. Although subjectivity is often con- venient, as the participant himself usually knows the best how he is feeling, his answers might be biased. Therefore, involving another, more objective, method of measuring sickness can overall provide more accurate data.
The Simulator Sickness Questionnaire is the most widely used questionnaire for as- sessing simulator sickness [2]. The intent of the Simulator Sickness Questionnaire was to analyse sickness caused by flight simulators. However, the questionnaire objectives are applicable for sickness induced by simulators in general, including VR [8].
The Simulator Sickness Questionnaire collects answers regarding 16 symptoms of a sickness caused by simulators. Based on the respondents’ answers, the questionnaire can suggest information about the specific form of sickness [8].
Postural Stability Test
As opposed to a questionnaire, postural stability tests are considered to be more objec- tive and less prone to bias [8]. Postural stability tests measure functioning of sensory information from visual, somatosensory and vestibular systems that all participate in maintaining balance [22]. Inability to maintain balance can indicate dizziness or vertigo, which are both symptoms of motion sickness.
The Tandem Romberg test is a postural stability test which can detect problems in keeping balance [22].
Figure 1.2:During the Tandem Romberg postural stability test, a participant is standing upfront with his feet placed directly or partially in front of one another [22].
The Tandem Romberg test is performed in the following way:
1. A participant is standing upfront with his feet placed directly or partially in front of one another, as shown in Figure 1.2.
2. The participant’s arms are crossed over his chest.
3. The participant performs the test first with open and then with closed eyes.
4. The Tandem Romberg test is positive if the participant’s body sways, the participant cancels the tandem position of his feet or even falls down [22].
Note that, obese and elderly participants might be unable to maintain balance in the described position and therefore, a positive Tandem Romberg test might not directly indicate a malfunction of sensory systems [22].
Physiological Measures
Another objective form of testing sickness is a whole range of physiological measures.
The physiological indicators that point at an occurrence of sickness are heart rate, blink rate, electroencephalography results, or cold sweats. Note that it is usually not deter- mined if a change in a physiological measure caused by sickness is an increase or a decre- ment. It is due to the fact that those changes may differ across individual participants [8]. For example, when sickness arises, the heart rate of one participant may increase, but the heart rate of another participant may decrease. Therefore, it is suggested comparing changes in those measures relative to an individual, instead of analysing those measures among multiple participants [8].
1.4 Locomotion
Travelling, walking, or any sort of moving is essential in any real-life experience. A virtual experience is no exception, as the ability to move a user around a scene enhances immersiveness, or plays a significant part in story-telling or overall functioning of the VR application. Locomotion is an often-used term in VR sphere. Locomotion refers to the act of moving from place to another place [15]. In this thesis, the word locomotion refers to the process of moving a user through a virtual scene in a VR experience.
This chapter discusses frequent techniques used for locomotion, as well as design guidelines for locomotion in VR.
1.4.1 Locomotion Techniques
Navigating a user through a scene (locomotion) can be accomplished in multiple different manners. However, few of them are considered a good practise, as they reduce the risk of a user’s discomfort or motion sickness. Motion sickness is discussed in Section 1.3.
Also, none of the methods is regarded as the best practice, since all of them work to a certain extent in certain cases. It is recommended to consider offering users multiple options of locomotion techniques to choose from, in order to uplift user experience and reduce the risk of discomfort [13].
Real-world Walking
Real-world walkingsimply requires a user to walk in the real world, which then causes to update the position of the user’s viewpoint in the virtual world. The main benefits of using this method are intuitiveness, as well as the absence of motion sickness. However, this method works until the user reaches the boundaries of his real-world playground.
For that reason,Real-world walkingdoes not usually suffice as a locomotion technique by its own. Nevertheless,Real-world walkingcan be combined with other locomotion meth- ods in such a way that when a user reaches the real-world boundaries, he can continue with navigating virtually.
Artificial Locomotion
One of the most basic locomotion techniques is simply linear moving a user’s viewpoint in a virtual scene, while the user is stationary in the real world [13]. This method uses VR controllers and is not difficult to implement, as it can be achieved by mapping the user’s input from the controllers to translate the avatar, or the scene, respectively. The main drawback of using this method is the high risk of motion sickness [8], which is discussed in Section 1.3.
Teleportation
When usingTeleportation, a user indicates its desired location in the scene, in order to teleport to that location immediately. This method does not induce visual motion of the scene and therefore, does not cause motion sickness. In addition, this technique can be implemented effortlessly, as a default Teleportation solution is often provided by a VR platform the experience is developed for. Teleportationcan, on the other hand, cause a user’s disorientation. It is suggested indicating the direction which the user will be facing after the process of teleportation [13].
Walk About
Walk aboutis yet a pioneering locomotion technique that incorporates Real-world walk- ing. A user can freely walk until he reaches the borders of his physical area. Then, the user presses and holds a button to enter a special mode that freezes the VR experience.
This mode allows the user to turn around in the real world, having the boundaries be- hind his back. After, the user can leave the freeze mode and continue walking in the same direction in the virtual world [27].
Blink Turn
Blink turnis a technique used for rotating a user’s viewpoint when controllers are used for performing the viewpoint rotation. In order to reduce motion sickness caused by scene motion, viewpoint turns black, while the camera turns by a predefined value [33].
Note, that a user’s full body rotation in real world might be more suitable for per- forming viewpoint rotation. The reason for that is the absence of scene motion, as well as the intuitiveness of such action.
Tunnel Vision
By narrowing the field of view, motion sickness can be reduced. A developer can create tunnel vision by fading the scene peripherals or incorporating some peripheral-blocking objects, such as a helmet [13].
Walking in Place
Walking in placeis a technique allowing for locomotion in VR in a similar way that one is moving in the real world. A user is lifting his feet in a way that resembles walking, but the user is not displacing in the real world. This locomotion method can be achieved in various ways, for example, using an additional accelerometer to measure the movement of a user’s limbs, or even using only VR controllers [32].
Walking in place engages the vestibular system with the body movement and head bobbing, which can reduce motion sickness [32]. A downside to this method is an un- comfortable feeling a user might experience when pretending to walk, but not actually going anywhere.
An alternative to a user lifting legs in an unnatural way, as described above, is us- ing a motion platform as a piece of hardware integrated to the VR experience, where a user can walk freely. When using motion platforms, motion sickness can be reduced or suppressed completely.
Arm Swinging
Arm swingingis a locomotion technique that requires a user to sway his arms while gaz- ing at one direction, in order to move at that direction. Similarly toWalking in place,Arm swinging uses accelerometers attached to users’ arms to perform locomotion, or can be achieved using VR controllers [32]. Arm swingingcan be suitable for experiences simu- lating zero-gravity space.
Motion Platforms
Motion platforms are hardware devices on which a user is standing or actively walking while wearing a head-mounted display. Motion platforms can add to the immersiveness of a VR experience, as a user is allowed to roam freely in the virtual environment. Using motion platforms possibly prevents motion sickness. However, they have to be well- calibrated, as well as thoroughly integrated into the VR application design, in order to overcome sensory conflicts [8].
1.4.2 Locomotion Design Guidelines
Proper locomotion design and implementation are crucial for every VR application, as poor locomotion design can cause a user feeling discomfort or sickness, as discussed in
Section 1.3.
This chapter summarizes design guidelines for moving a user through a scene with- out causing health side effects.
Accommodation to Sickness
Having experience in VR, a portion of users is likely to adapt to various locomotion means and is, therefore, less prone to feeling sick. However, when designing a VR expe- rience, a designer should keep in mind users that may be a novice in VR or even sensitive to motion sickness. For example, a VR designer should allow for more variants of lo- comotion techniques in his VR experience, in order to reach a broader range of users [13].
Similarly to the effort, a VR designer should make not to overwhelm users with in- tense content at the beginning of his VR experience, a VR designer should initially avoid locomotion techniques plausible to inducing motion sickness.
No Locomotion
The most effective mean of moving a user through a scene is not using locomotion at all [13]. As long as it complies with an application narrative, a VR designer can invent ways that allow for a change of the scene by only mimicking the movement. In the Oculus VR Locomotion Design Guide [13], examples for no-locomotion design, such as riding an elevator or making a user’s view turn black by losing consciousness, are provided.
Acceleration
As discussed in Section 1.3.2, the main stimulus inducing motion sickness is considered to be an acceleration. In other words, when a user’s movement is speeding up, slow- ing down or even turning direction, the risk of motion sickness significantly increases compared to moving at a constant velocity. According to J. Jerald [8], the risk of mo- tion sickness might increase with a longer acceleration duration. Therefore, conversely to what one might think, if acceleration cannot be omitted completely, a VR designer should aim for greater acceleration, but for a shorter period of time.
Motion Speed
The risk of motion sickness does not correlate linearly with the size of velocity of the motion. In fact, a normal human pace velocity, between 1.4 m/s and 3 m/s, is considered to be more sickness-inducing than very slow velocity or unnaturally rapid velocity [13].
Motion Direction
The direction of a user motion can be sickness-inducing, as some movement directions are unnatural for a human in the real world. The forward movement is what one is used to in the real world, whereas moving backwards or even sideways is rare, therefore a VR designer should refrain from allowing moving a user in those directions [13].
User in Control of Viewpoint
People driving a vehicle rarely suffer from motion sickness [23]. Despite this fact, the same people can experience motion sickness when they are in a moving vehicle but not
actively controlling the speed and direction of the movement. Similarly, in VR, a user can feel less discomfort when he is actively managing his viewpoint [8].
Standing vs Sitting
The risk of sickness during a VR experience is higher for standing users, as opposed to users that are sitting [8]. Also, there is a risk of a user injuring himself when losing stability in a standing position.
Height of the Viewpoint
A user is more likely to feel discomfort when his viewpoint is situated at a different height than his real-world physical height [8].
Stationary Objects
Motion sickness is probably induced by a sensory conflict, as discussed in Section 1.3.1.
The risk of motion sickness can be reduced by providing some visual stimuli, that sup- port the information from the vestibular system. Looking back at the example of reading a book in a moving car, mentioned in Section 1.3, the discomfort can fade away when one looks out of the car window and perceives moving surroundings, which supports what is sensed by the vestibular system. In VR, inversely, when one is moving virtually, the eyes perceive motion, but the vestibular system does not. Similarly to the moving car ex- ample, adding some stationary objects to the scene that are in accord with the vestibular system can significantly reduce motion sickness [8].
Leading Indicators
When a user movement is following a predetermined trajectory, the motion sickness can be reduced by adding objects indicating the direction of the movement to the scene.
With these indicators, a user can predict the changes in the viewpoint, which can reduce discomfort [8].
1.5 Latency
Latency is the time taken by a system to provide a response to a user’s action [9]. Al- though no system can have exactly zero latency, a VR developer should strive to achieve as low latency as possible.
Latency in a VR system causes a user’s viewpoint to move with a delay when one is moving their head in real life. In such a case, the virtual world is moving while a user is still. This unintended world movement is called swimming [8] and can be the cause of inducing motion sickness. Since the user’s eyes perceive motion as the scene is swimming and the user’s vestibular system at the same time detects no motion, a sensory conflict occurs and possibly causes motion sickness [8], as discussed in Section 1.3.
Other latency consequences in VR include distracting from the sense of presence or degraded vision [8].
There is probably no ideal latency value developers should aim for, except that it should be as low as possible. The lowest perceivable latency value is around 3.2 ms.
Interestingly, users are sensitive to changes in latency, therefore a stable latency is im- portant even at higher latency rates. Also, latency can be easier detected with faster head movements [8].
Latency requirements are generally higher for augmented reality systems where it should not exceed 1 ms. The reason is that the user is able to objectively judge the dif- ferent behaviour of the real-world objects and the virtual scene [8], as one perceives the real environment and the virtual one at the same time.
1.6 Frame Rate and Refresh Rate
Frame rate is the frequency at which frames are displayed to a user [26]. Similarly, frames per second (FPS) is the number of frames displayed in a single second. Conversely to latency, the higher FPS is, the better the experience.
However, FPS can be limited by the refresh rate value. Refresh rate, similarly to frame rate, is the frequency of displaying frames on a device. The difference between the frame rate and refresh rate is that refresh rate is usually fixedly specified with monitors and projection devices [26]. For instance, the Oculus Quest device supports a 72 Hz refresh rate at maximum [13], allowing for a maximum of 72 FPS in an experience.
Postural Stability
Since this thesis involves implementing an application for proprioceptive training, the relevant terms of postural stability should be defined ahead. This chapter introduces the fundamental terms of postural stability and the information about the Posturomed balance platform.
2.1 Posture
Posture can be defined as the position of body segments, held against affecting forces, usually the gravity. Posture accompanies every motoric activity the body performs [30].
The human body in its standing posture is indeed an unstable system, with its base cov- ering a small surface and a high center of gravity. Posture is a complex system and does not only concern the muscle contraction and joints positions. It also involves the visual and vestibular system as a perceiver and the central neural system as a coordinator [30].
Optimal posture can be explained as the most efficient posture in order to stand up- right. The optimal posture requires minimal muscle contraction, as well as joint com- pression [17].
Postural stability is the ability to keep an optimal posture by reacting correctly to changes in both the inner and outer environment. Postural stability is a condition for reducing the risk of falls [30].
2.2 Falls and Their Prevention
Falls are a serious concern regarding older adults. Falls can cause minor and major in- juries, leading to motoric malfunction, loss of autonomy, or other falls. In the worst cases, injuries caused by falls can be fatal. In fact, "falls are the second leading cause of uninten- tional injury deaths worldwide," [21] with the greatest number of fall fatalities occurring among adults older than 60 years.
Falls may be caused by movement and balance disorders, unexpected events, vertigo, pain, terrain unevenness, inappropriate footwear, and so forth.
To reduce the risk of falling, fall prevention interventions can be taken. Some of the recommended interventions are consistent exercising, using an assistive or compensatory equipment, rehabilitation, or vitamin supplements [11].
Due to falls being a major public problem, strategies for fall prevention involving modern technologies have been emerging. The technologies utilised for fall prevention incorporate predictive analytics, monitoring technologies, wearable sensory devices, or robotics [20].
In addition, there are efforts to deploy virtual reality into fall prevention interven- tions. Several studies have examined the effects of virtual reality on postural stability and balance and presented contemplative results [10, 12, 16].
2.3 Posturomed
Posturomed is a neuro-orthopaedical therapeutical device invented by Eugen Rašev in cooperation with the Faculty of Physical Education and Sport at Charles University [3].
The Posturomed device generally consists of an unstable platform one is standing on and a pair of railings, which one can hold onto. The therapeutical device functions based on a method where the unstable platform is oscillating in the horizontal directions. Training with Posturomed can improve joint muscle coordination and, therefore, ameliorate the overall posture [3].
Figure 2.1:The Posturomed balance platform [31]
Design
This chapter discusses the design process of PhysioTrails. Firstly, it generally states the purpose and the intended usage of the system. Furthermore, this chapter analyses the requirements of the system, as well as the overall system architecture. It provides reason- ing why particular solutions were decided to be used with respect to the design guide- lines in VR, presented in Chapter 1.
3.1 System Background and Usage
The PhysioTrails is designed to be used in Nová Slunečnice retirement home. The pur- pose of the system is to aid a therapeutic process, during which an elderly patient per- forms proprioceptive exercises with a physiotherapist as a supervisor. This thesis intends to provide an application in virtual reality that inspirits the otherwise ordinary process and possibly improves a patient’s performance during exercising. In addition, this work’s result should provide the physiotherapist with a mobile application that allows them to observe and overall control the patient’s VR experience.
Already existing VR applications have been tested for this purpose in the retirement home and were proven beneficial. The already tested VR applications not only caused relief and made the exercise more pleasant for the patient, but also improved the patient’s proprioceptive performance in such way that the patient’s posture is more relaxed and so the exercises are more effective.
Figure 3.1:Schema of the PhysioTrails usage
3.1.1 Target User Group
The target user group consists of users of greater age, who may have minor postural stability difficulties. These users are supposed to have none or basic level of technical skills. However, the users have experience with VR usage, roughly knowing what to expect and, importantly, enjoy VR experiences.
3.1.2 User Roles
The system distinguishes two user roles in the following manner:
• Patientrepresents en elder performing proprioceptive exercises utilising the Pos- turomed balance platform. The patient is standing on the balance platform while wearing a VR head-mounted display during the whole rehabilitation process.
• Physiotherapistrepresents a physiotherapist conducting the rehabilitation process with a patient. The physiotherapist directs a patient in terms of exercising and observes a patient’s well-being and postural stability. The physiotherapist user role uses a mobile application to control the VR experience a patient is currently seeing in a head-mounted display.
3.2 System Architecture
The system consists of two distinct parts, namely a VR application and a mobile control application.
• VR applicationis run in a head-mounted display and provides a patient with a VR experience.
• Control applicationis run in an Android mobile device. It allows a physiotherapist to start and manage a VR experience run in the VR application.
3.3 Software Requirements
Software requirements are capabilities that must be fulfilled by a system to satisfy an agreement [29].
Software requirements can be generally classified into two types, the functional re- quirements and the non-functional ones. The functional software requirements state and describe the functionalities of the designed system. Non-functional requirements, also referred to as qualitative requirements, describe what is required of a system in terms of quality, such as performance, usability, or an overall user comfort.
Functional as well as non-functional requirements are further divided into the ones concerning the VR application and the ones concerning the control application. The re- quirements were defined mainly based on the needs of the Nová Slunečnice retirement home with regard to design guidelines for the Oculus platform [13]. A short clarification follows each requirement in order to explain the requirement itself as well as the motiva- tion behind it. Some of the requirements will not be implemented in the current versions of the applications. These requirements are marked with a star (*), and the reason why the specific requirement is not implemented follows.
3.3.1 Functional Requirements
VR Application
FRQ 1. The system allows a patient to immerse in a landscape travelling VR experience lasting 5 minutes
This requirement represents the core functionality of the VR application. The patient should be able to immerse themselves in a movement-visualising VR experience, as the apparent movement causes the patient’s body to move on the balance platform, which is indeed the desired proprioceptive exercise. The duration of the experience corresponds to the regular proprioceptive training schedule in the retirement home.
FRQ 2. The system allows a patient to select a specific VR experience
The ability to select a VR travelling scene is implemented in both VR and con- trol applications. The reason for that is the option for the physiotherapist to choose the preferred workflow and prevent the single point of failure in case of poor networking conditions or the control application not working. There should be three VR experiences to choose from.
FRQ 3. The system allows a patient to see a virtual representation of their hands that is accurate to their position and movement
During the proprioceptive exercising, patients usually hold onto the railings of the Posturomed balance platform. Hence, the use of hand tracking instead of VR controllers is essential. The absence of controllers may also ease the routine the physiotherapist undergoes during the proprioceptive exercising, as they have free hands during the process.
FRQ 4. The system allows a patient to pause and resume an ongoing VR experience*
This requirement is not implemented because there is eventually no need for patients themselves to pause a VR experience. This functionality is left on the physiotherapist, as they can pause and resume an ongoing VR experience with the control application. The presence of UI elements or any button objects in the VR travelling scene could also distract the patients.
FRQ 5. The system allows a user to calibrate the virtual world with the real world
Since the patient’s virtual hands are displayed during the VR travelling experi- ence, as already defined atFRQ3, a notional bridge between the virtual and the real world is created. The Posturomed balance platform, which the patient is standing on and hold onto during the experience, represents another notional bridge between the VR and the real world. Since the patient can feel the railings of the balance platform with their hands, the balance platform should also be present in the virtual world. However, in order for the feel sensation of railings in the patient’s hands to comply with the visual representation of the same rail- ings in VR, the virtual world should be properly calibrated. In other words, the virtual representation of the balance platform should be drawn at exactly the same position as it is in the real world, not to hinder the overall immersiveness of the experience.
The first idea of the calibration process represented a fully automatic one, with VR controllers permanently attached to the Posturomed balance platform.
That way, the application could use the data concerning the position of the VR controllers to draw the virtual balance platform at the correct place. How- ever, there is an overhead with either detaching the controllers when they are needed to be used or attaching the controllers every time the calibration of the PhysioTrails application is needed.
Instead, an approach when hand tracking is used for the calibration is chosen.
This way, a user indicates points on the real-world balance platform that are used to position the virtual balance platform correctly. The calibration process takes place each time the PhysioTrails application is started. This procedure should take no more than a minute and can be performed after defining the play area, which is required by the VR device, as it also should be completed regularly. The calibration process is meant to be performed by the physiothera- pist, as they usually start the VR application, but the process should be overall intuitive in a way that a patient with less technical skills can manage to com- plete it.
The calibration process can be seen in the activity diagram in the following Figure 3.2.
Figure 3.2:Activity diagram illustrating the calibration process
FRQ 6. The system allows a user to skip the calibration process
In case the accuracy of the position of the virtual vehicle is not crucial, e.g., a patient is not holding the railings of the balance platform during the exercises, the calibration process can be omitted. When the calibration is skipped, the vehicle is drawn at a default position.
Control Application
FRQ 7. The system allows a physiotherapist to connect to the VR head-mounted display This requirement is essential for the ability to use the control application, and therefore crucial for fulfilling the following control application requirements.
The process of the control application connecting to the VR application can be seen in the activity diagram in Figure 3.3.
FRQ 8. The system allows a physiotherapist to select a specific VR experience
As mentioned at theFRQ2, this requirement is the same for both VR and con- trol applications. The activity diagram Figure 3.4, representing the control application connecting during the scene selection illustrates this requirement.
Figure 3.3: Activity diagram displaying Scenario 1: Control and VR applications connection process
Figure 3.4: Activity diagram displaying Scenario 3: Control application joining VR application during scene selection
FRQ 9. The system allows a physiotherapist to start a specific VR experience
When the control application is connected to the VR application, the move- ment in the travelling VR experience is not started until the physiotherapist commands to start the training with the control application. The reason for that is for the physiotherapist to make sure the patient is ready and initialise the exercise only if it is true.
The activity diagram in Figure 3.4 illustrates this requirement.
FRQ 10. The system allows a physiotherapist to skip the calibration process
This requirement, similarly to theFRQ6requirement, allows a physiotherapist to skip the calibration process.
This requirement is illustrated in the activity diagram in Figure 3.5.
Figure 3.5:Activity diagram displaying Scenario 2: Control application joining the VR applica- tion during the calibration process
FRQ 11. The system allows a physiotherapist to join the VR application during an ongoing VR experience
The physiotherapist should be able to join the VR application when there is al- ready a VR travelling experience running. In that case, the control application should prompt the physiotherapist about the ongoing VR experience and allow displaying the patient’s viewport without waiting until the experience finishes.
This scenario is demonstrated in Figure 3.6.
Figure 3.6:Activity diagram displaying Scenario 4: Control application joining the VR applica- tion during an ongoing VR experience
FRQ 12. The system allows a physiotherapist to view a patient’s viewport in an ongoing VR experience
In order for the physiotherapist to see how the VR experience carries on and to better predict a patient’s movements on the balance platform in the near future, the physiotherapist should be able to display the patient’s viewport in the control application.
FRQ 13. The system allows a physiotherapist to view a patient’s current time progress in an ongoing VR experience
FRQ 14. The system allows a physiotherapist to view a patient’s current location in an ongo- ing VR experience environment
The physiotherapist should be displayed the time the ongoing experience has lasted so far and have at least a rough idea about how much time left there is until the VR experience finishes.
FRQ 15. The system allows a physiotherapist to end an ongoing VR experience
The VR user is automatically brought back to a landing scene after the VR experience finishes. Still, the physiotherapist should be able to end the VR experience anytime, in case it has to be quit prematurely.
FRQ 16. The system allows a physiotherapist to pause and resume an ongoing VR experience The physiotherapist should be able to pause and resume an ongoing VR expe- rience with the control application in a situation requiring this action, e.g., a patient suffering from motion sickness.
FRQ 17. The system allows a physiotherapist to set the speed of travelling in an ongoing VR experience
The physiotherapist should be able to change the travelling speed of an ongoing VR experience to adjust the experience to each patient individually. There are five different speed levels to choose from. The default value should be set to an optimal speed, which satisfies a broader range of patients.
3.3.2 Non-functional Requirements
VR Application Availability
NRQ 1. The system is available to use on the Oculus Quest VR headset.
Virtual scene
NRQ 2. The virtual scene represents a landscape situated outdoors
The landscape in the VR travelling should be situated outdoors, as the outdoors allow for multiple visually interesting stimuli and also justify unevenness of the terrain, which is discussed inNRQ3.
NRQ 3. The motion path in the VR experience should contain unevenness
The movement should contain multiple bends and bumps. When an appar- ent bump is ahead, the patient unintentionally changes their posture in order to compensate for the upward movement in the near future. The same also applies to bends and other terrain unevenness. These micro-movements and changes in the patient’s posture are essential for the proprioceptive training on the balance platform.
NRQ 4. The virtual scene represents a landscape familiar to a user
This requirement represents the need for a realistic landscape that possibly does not overwhelm the patient in any way.
NRQ 5. The virtual scene visualises pleasant landscape that should overall evoke positive emotions
The VR experience should evoke positive emotions, as the aim of the VR appli- cation is not only to aid the method of proprioceptive training but also to make a joyful experience from the ordinary process.
NRQ 6. The virtual scene contains unexpected stimuli for a user
Similar to the NRQ3, needing an uneven terrain, this requirement requests some unexpected stimuli that, distracting the patient to a small extent, may result in the change of the patient’s posture.
NRQ 7. User is navigated automatically through the virtual scene in a familiar means of transport
Since the patient typically holds onto the railings of the balance platform, they should not need to control the movement in any way. When the patient’s body is not displayed virtually, they still should be able to see some indication of where they are standing in the virtual world, so a means of transport indicating where they are standing can be a good option. The vehicle should be realistic and familiar to the patient in the same way as inNRQ4.
NRQ 8. User is navigated automatically through the virtual scene in a familiar means of transport
User comfort
NRQ 9. The system allows using an intuitive user interface suitable for non-experienced users
NRQ 10. The system allows using a user interface available in the Czech language
Performance
AllNRQ10,NRQ11andNRQ12performance measures were taken from the Oculus de- sign guidelines [13] and represent the quality traits necessary for an application to be published in the Oculus Store.
NRQ 11. The system performs less than 175 draw calls per frame NRQ 12. The system renders 750 000 - 1 000 000 triangles per frame NRQ 13. The system maintains 72 FPS at a stable state*
Although appropriate actions were taken, this requirement was not accom- plished, as discussed in Section 4.2.6.
Testing
NRQ 14. User testing on at least three users is performed on the system
The participants of the user testing of the VR application should correspond to the VR application target group defined in Section 3.1.1. The user testing process of the VR application along with its findings is discussed in Section 5.1.
Control Application Availability
NRQ 15. The system is available to use on an Android device
User comfort
NRQ 16. The system allows using an intuitive user interface
NRQ 17. The system allows using a user interface available in Czech and English languages
Testing
NRQ 18. User testing is performed on the system
The participants of the user testing of the control application should corre- spond to the control application target group defined in Section 3.1.1. The user testing process of the control application along with its findings is discussed in Section 5.2.
Figure 3.7: Use case diagram displaying the functionalities of the system. Grey functionalities are not implemented
3.4 Prototyping
Prototyping is useful for inventing how functionalities will be used via the user interface and laying out the overall design a final application will have. High-fidelity prototypes were created for the PhysioTrails control application.
The created prototypes can be seen in Figure 3.8.
Figure 3.8:High-fidelity prototype of the control application
3.5 Existing Solutions
When designing any software product, studying other already existing solutions can bring valuable information for the design and implementation phases of the develop- ment. Virtual reality for commercial use is certainly not yet expanded to its full poten- tial, so no application with similar use cases was found. Instead, an application already tested with the retirement home for the same purpose as PhysioTrails was decided to be analysed.
3.5.1 Epic Roller Coasters
Epic Roller Coastersis a VR application for the Oculus Quest platform, available inOculus Store. It offers a rollercoaster riding experience in various fictional and realistic worlds.
A user rides in a roller coaster cart-like vehicle on steep railways. The speed of the course is optimal, so a user can either enjoy the view of the world when taking lower speed, or feel the sensation of a rapid roller coaster experience another time. The application offers three different play modes. Firstly, in the classic mode, a user gets to ride a roller coaster and freely look around the surroundings. In the shooter mode, a user focuses on aiming and shooting on targets while riding a roller coaster. Finally, in the race mode, a user can take control of the velocity and, to a limited extent also the direction of the vehicle, and compete with their peers.
Epic Roller Coasters is free of charge, including 9 worlds but offers 17 paid ones as an extension.
The Epic Roller Coasters application was used in the retirement home during pro- prioceptive training along with the Posturomed balance platform, as it contains linear movement along winding paths.
Motion sickness
The Epic Roller Coasters application developers are aware of the possibility of inducing motion sickness, and the application thereafter provides motion sickness counter actions.
A user can virtually put on a helmet with voluntary blindfolds. The helmet, along with the blindfolds, covers the peripherals of the user’s vision, which can lead to reducing motion sickness, as discussed in Section 1.4.1.
The experience is designed for the sitting position, as in the experience a user is seated in a roller coaster cart. However, a standing position is also possible without interven- ing in the immersiveness, which can reduce the rate of motion sickness, as discussed in Section 1.4.2.
During the testing of Epic Roller Coasters for this analysis, I experienced multiple motion sickness symptoms. Apart from the fact that the motion sickness syndromes can partially result from speedy motion, the viewpoint shifting occurring when taking turns was found nauseating in both standing and sitting positions. The application performs viewpoint movements to orient a user in the direction of the railway. These changes in viewpoint rotation might have been the primary cause of motion sickness in this VR experience.
Multiple reviewers of this application on Oculus Store state they have experienced motion sickness, which perhaps leads to the application’s average rating.
It should be noted that during the application testing with the Posturomed balance platform in the retirement home, the patients did not experience any significant symp- toms of motion sickness.
Implementation
This chapter discusses the implementation of PhysioTrails. It presents the technology stack used for the implementation along with the motivation behind using the mentioned technology. The following sections describe the implementation of the both developed applications.
4.1 Technology Stack
4.1.1 Unity
Unityis a game engine for the development of 2D and 3D games [25], supporting vast amount of platforms. Unity covers typical problems of game development to which it provides solutions with premade integrable components. It offers a user interface for creating a scene and allows scripting using the C# programming language. In this thesis, Unity was utilised for the development of both the VR application and the control ap- plication. The unity engine was then further enhanced with packages that are described further in this section. Creating 3D games, especially those for virtual reality, is more efficient when facilitated through a game engine. Game engines have numerous bene- fits, from straightforward scene manipulation to the analysis and debugging options to the versatility of building the developed application on various platforms. Moreover, the Unity engine was chosen over other available game engines for its vast number of active users, possibly offering a troubleshooting discussion, a great collection of assets and existing solutions in its asset store, and supposedly better performance on mobile devices.
4.1.2 Autodesk Maya
Autodesk Mayais a graphics editor allowing for creation of 3D models, their animation and rendering. Models built inMayacan be then further utilised in the game industry or cinematography. Maya is supposedly profoundly utilised in the professional sphere. The assets created for the purpose of this application are rather simple, and Maya was used because of previous experience with the tool. In this thesis, assets used for creating a virtual scene were created using this tool, including a cart model as a means of transport in the VR application.
4.1.3 Substance Painter
Substance Painter is a 3D painting software for texturing and rendering 3D objects [1].
Substance Painter allows painting textures directly on a 3D model and thereafter ex- porting the textures in image formats. Substance Painter offers a modern and intuitive
solution of creating textures for a 3D model. In addition, Substance Painter offers a solid base of ready to use textures, either contained within the tool itself or being a product of the community of the substance painter users. Substance Painter allows exporting the textures in various templates, including the ones for Unity. In this thesis, Substance Painter was used for texturing assets created in Maya.
4.1.4 Figma
Figmais an online tool mainly for prototyping and creating vector graphics. During the implementation, Figma was used for creating elements for user interface in both control application and VR applications. High-fidelity prototypes of the control application were also made in Figma.
4.1.5 Unity Packages
In order to grasp the full potential of the Unity game engine, one may take advantage of the Unity Asset Store, which contains a great number of 2D and 3D assets, but also various ready-to-use tools, as existing solutions of common game development problems.
The list of used Unity packages accessible from the Unity Asset Store, can be seen in Table 4.1 below.
Table 4.1:Unity packages with their usage
Package Name Usage
Oculus Integration VR support for Oculus devices
Mirror Networking API, used for communication between
VR application and control application
ParrelSync Multiplayer testing directly in the Unity editor, used for testing of the communication between VR appli- cation and control application
Bézier Path Creator Editor for creating paths, used for camera movements and animations
Photoscanned Mountain Rocks Nature assets used for scene creation Rocky Hills Environment Nature assets used for scene creation Flooded Grounds Nature assets used for scene creation
Animal pack deluxe Animal assets used for scene creation and animations Outdoor Ground Textures Textures used for scene creation
Grass Flowers Pack Free Textures used for scene creation Conifers [BOTD] Nature assets used for scene creation HQ Autumn Dry Maple Trees Nature assets used for scene creation Snowy Mountain Nature assets used for scene creation Stylised Nature Pack Nature assets used for scene creation Nature Starter Pack Nature assets used for scene creation The Tales Factory Nature assets used for scene creation
AllSky Free Sky cubemaps for scene creation
Terrain Tools Sample Asset Pack Collection of for theTerrainobject sculpting Memory Profiler Tool for the analysis of allocated memory
Graphy Tool for displaying FPS, allocated memory and other analytics
