Tomas Sokoler
email: sokoler@itu.dk

Naveen L Bagalkot
email: naveen@srishti.ac.in

Watching Your Back While Riding Your Bike

Keywords: Motorbike Riding, Embodied Self-monitoring, Constructive Design Research, Interactive Sketching

de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

"If you know bikes at all, you can tell a lot about a man by how he rides. Abdullah rode from reflex rather than concentration. His control of the bike in motion was as natural as his control of his legs in walking. He read the traffic with a mix of skill and intuition. Several times, he slowed before there was an obvious need, and avoided the hard braking that other, less instinctive riders were forced to make. Sometimes he accelerated into an invisible gap that opened magically for us, just when a collision seemed imminent." [START_REF] Roberts | Shantaram. Abacus. 19. The Motorcyclist's Workout[END_REF].

In this paper, we explore the design of digital technology aimed at mitigating the risk of lower back pain injuries caused by the physical stress experienced as part of the daily motorcycle commute through dense urban traffic. In particular, we look into the design of a system that, by making cues on the rider's back posture available seeks to enable and encourage bike riders to carry out preventive measures as an integrated part of riding.

A large number of people use motorcycles to commute in India. As per Bangalore Traffic Police, Bangalore had about 3.8 million two-wheelers (which includes both motorbikes and scooters) in March 2015. Commuting in Indian traffic involves not only negotiating dense traffic, but also traffic that is erratic with no lane-discipline, and bad road conditions (see figure 1). Motorbike commuting in such conditions is physically stressful, as the rider has to ride for longer durations by sitting in uncomfortable positions required to balance the motorbike in slow moving and erratic heavy traffic [START_REF] Sai Praveen | A study on Motorcycle usage and comfort in urban India[END_REF]. It requires the rider to continuously adjust the steering utilizing the upper body [START_REF] Either | Motorcycle-Rider Servomechanism Steering Theory[END_REF]. The constant adjustments of the upper body lead to high repetitive loading on the musculoskeletal system, particularly in lower back region [START_REF] Sai Praveen | A study on Motorcycle usage and comfort in urban India[END_REF]. Furthermore, research has shown that maintaining the same lean-forward posture for longer duration, while navigating the city traffic causes fatigue in lower back muscles [START_REF] Velagapudi | Muscle Fatigue due to Motorcycle Riding[END_REF]. Orthopedics and physiotherapists suggest the riders to strengthen their core back muscles to reduce the musculoskeletal strain through core strengthening exercises [START_REF] Akuthota | Core Stability Exercise Principles[END_REF]. However, adhering to this kind of traditional exercising require that the riders take time out of their busy schedule to exercise as a distinct activity beyond, and detached from, the daily commute. Realising this challenge, therapists suggest that the riders perform back stretching exercises while sitting on the bike either during a break or immediately before or after riding (see figure 2). We see this as an example of a general move in the field of physiotherapy towards a more individualized approach (for e.g. [START_REF] Mastos | Goal-Directed Training: Linking Theories of Treatment to Clinical Practice for Improved Functional Activities in Daily Life[END_REF][START_REF]National whitepaper on rehabilitation[END_REF][START_REF] Nicholls | The body and physiotherapy[END_REF]) aiming to better integrate exercising as part of existing everyday activities. Saving time, one could imagine that riders, for example, would do the stretching exercises while holding still at traffic lights. However, as we observe in Indian city traffic most bike riders do not make a complete stop at traffic lights, but instead push the bikes using their feet to get in position (see figure 1).

Taking the suggestions by the physiotherapists even further we want to explore if and how part of the most basic lower-back strengthening exercises could be integrated with the activity of actually riding the bike. Grounded in related research on the design for physical rehabilitation [START_REF] Bagalkot | Designing for Lived Informatics in Out-Of-Clinic Physical Rehabilitation[END_REF][START_REF] Bagalkot | Reride: Performing Lower Back Rehabilitation While Riding Your Motorbike in Traffic[END_REF][START_REF] Bagalkot | Embodied-self-monitoring: Embracing the context for adherence to physical rehabilitation in the design for self-monitoring[END_REF][START_REF] Bagalkot | Integrating physiotherapy with everyday life: exploring the space of possibilities through ReHandles[END_REF][START_REF] Bagalkot | Unboxing the tools for physical rehabilitation: embracing the difference between the clinic and home[END_REF] we speculate that presenting the riders with an opportunity to perform preventive self-care as part of riding will lead to a higher degree of adherence. In particular, guided by the theoretical construct of 'embodiedself-monitoring' [START_REF] Bagalkot | Designing for Lived Informatics in Out-Of-Clinic Physical Rehabilitation[END_REF][START_REF] Bagalkot | Embodied-self-monitoring: Embracing the context for adherence to physical rehabilitation in the design for self-monitoring[END_REF], we explore if and how, digital technology could help bring forward opportunities for the riders to perform basic adjustments to their ride posture while riding. As a first principle, our design to support in-situ body posture adjustment obviously has to take second place to the primary task of navigating the motorbike safely through dense traffic. Hence, basic adjustment of posture involves simple stretching and activation of the muscles of the lower back while leaving the hands free for the most crucial task of steering.

Without having any clear preconceived constraints to our design, other than the before mentioned first principle, and general therapist input on relevant basic adjustments, we set out to explore and narrow in on the kind of experience and interaction a system like this should enable. We did so by engaging in a process of co-exploration with riders experiencing our interactive sketch while riding. In terms of a broader research framing, the work reported is part of a series of research-through-design studies guided by the overall vision of mobile&pervasive digital technologies designed to encourage and enable people in turning mundane activities of everyday life into opportunities for preventive self-care.

Design exploration

We take a construction oriented research-through-design approach [START_REF] Koskinen | Design research through practice from the lab, field, and showroom[END_REF]. In particular, we engage in a process of sketching where interactive soft&hardware sketches act as our main vehicle for inquiry as the key facilitator of in-situ co-exploration with actual riders and while riding. Hence, we seek to engage stakeholders in a dialogue, and process of co-exploration, anchored in actual, however brief and sketchy, first hand experience.

In line with Buxton [START_REF] Buxton | Sketching User Experiences: Getting the Design Right and the Right Design[END_REF] we emphasize the evocative nature of sketching throughout this process and how what we look for in the collaboration with the riders are suggestions and openings for further design rather than conclusive statements on usability and particularities of our sketch. Informed by initial observations of motorcycle rides and guided by the theoretical construct of embodied self-monitoring, we started to envision, through scenarios, how data on back postures could be made available to encourage acts of preventive self-care while riding. In parallel, and as a fully entangled part of the envisioning process, we started work on the interactive ReRide soft&hardware sketch that would allow us to engage four riders as in-situ coexplorers.

Adding cues on back posture to the experience of motorbike riding

To get an initial report on the world of motorbike commuting in dense traffic one of the authors wore a GoPro camera on his helmet to video-record a ride from work to home. Inspection of the video soon turned our attention to the ways the rider, like Abdullah, constantly engage with a range of cues as he weaves in and out of traffic. The most easy to identify cues at play had to do with the presence and movement of nearby vehicles, the condition of the road, and of course the movements of the motorcycle experienced through the rider's direct bodily interaction with the bike.

What if data on Abdullah's body posture were made available alongside the many other cues that he experiences from the environment and the bike as he skillfully moves through traffic? How would Abdullah experience this? Could taking in visual cues on his back posture and adjusting his back accordingly be fully worked-in as part of Abdullah's driving?

Looking further to the rider's interaction with the bike we notice how cues from the environment, in many cases experienced as direct bodily interaction with the bike, is combined with visual cues taken in by the occasional glance at the dashboard with its selection of standard gauges (speedometer, tachometer oil pressure, fuel level, etc.) availing data on the state of the motor cycle. This seems to suggest a presentation of cues designed for continuous presence in the rider's field of view but at the same time, most important, designed with a low demand for attention along the lines of the design for glanceability [START_REF] Consolvo | Activity Sensing in the Wild: A Field Trial of Ubifit Garden[END_REF], as we aim for a minimum of interference with the primary task of navigating the bike safely through traffic. In a first attempt, this made us look for ways to piggyback on the dashboard design and placement as well as the rider's familiarity with the reading-at glance of the standard gauges. In effect, this in fact opened a much broader space of opportunity for design as it, in general, encouraged us to expand the kind of information made available on a motorbike to encompass not only data on the state of the bike but also data on the condition of the rider.

The ReRide scenario

As one of the very first steps in the process of sketching we formulated the idea of ReRide, as captured by the following scenario: Diva commutes to her work on her motorbike daily. She has been doing so for the past 5 years, and now is in the danger of developing repetitive strain injury of her lower back. To prevent the injury she has to perform stretching exercises, but she does not have the time or the energy at the end of day to do so. She then starts using ReRide. ReRide consists of two parts: a) A belt that is worn on the lower back sensing the position of the back (see figure 3) and b) a display unit that displays this information real-time, next to the motorbike's speedometer. As Diva rides her bike through the traffic she gets continuous feedback of her lower-back posture and adjusts her riding position in accordance with advice from her physiotherapist on preventive exercising.

The ReRide Interactive Sketch

In line with the open-ended nature of our early explorations we constructed a very basic interactive soft&hardware sketch using the Arduino platform. We fixed a passive resistor based flex sensor on a back support belt as the sensing unit (see figure 3). Data from the belt was input to the Arduino and in turn used to drive a LED bar display. When the rider bends their lower-back, resistance of the flex sensor increases. The Arduino board detects this increase as a change in analog input signal level and lights up a LED on the LED bar; the more the rider bends their lower-back the more number of LEDs light up on the LED bar. Our mapping of the increase in resistance in the flex sensor to the LED bars is an approximation aimed purely at exploring the basic experience of riding with the data. The data measured this way clearly lacks the precision needed if they were to be considered as 'true' measurements of the rider's lower-back posture.

The LED bar display was placed on the dashboard of the motorbike (see figure 4).

Experiencing ReRide

The interactive sketches helped us establish a dialogue with riders grounded in actual in-situ, however brief, first hand experience of what it would be like to have data on your lower-back posture available as visual cues while riding your bike. We asked four daily motorbike commuters, two men and two women, to go for rides with our ReRide sketch. One of the authors was riding pillion during this trial, with a video camera focusing on the rider and the ReRide display. Each ride lasted about 20 minutes and was followed by a brief discussion about the experience. Reiterating the intent of bringing forward our interactive sketches in the first place, we were not looking to test the particular design but rather trying to tap into riders reflections on the overall experience while aiming to get further input on where to take the general notion of making information on lower-back posture available as part of the riding experience.

What the Riders Did & Said

All the four riders mentioned that having access to their lower back data helped them to get a sense of their posture during the ride. One participant said, "Being able to see (data about) my posture helps, as I am usually aware of my bad posture only when it (lower back) starts to hurt." While the riders' opinions varied on how they will actually engage with the data while riding, they agreed that it added another layer of information for them to consider during the short ride with the sketch. In summing up the riders' experience of riding with ReRide we focus on two points brought forward across riders when discussing the role of lower-back cues as part of the act of riding.

"How About the Time Spent in the Same Posture?".

During the post-ride interview riders suggested that some kind of indication of the accumulated time spent in the same 'bad' back posture would help them make the decision on whether to adjust their back posture or not. Further, riders suggested that combining these accumulated back posture data with some sort of measure on time left to reach their destination would help them prioritize their decision to change posture in relation to their primary goal of reaching their destination safe and on time.

We observed several instances where preventive self-care clearly took second place to getting to the destination on time.

In one such instance, the rider had to brake as he approached a parked car and hence had to bend his back to balance the bike. This was reflected by the ReRide display increasing the lit LEDs from one to two. Slowing down could have been an opportunity for him to change his back posture, straightening it. However, as he at the same time identified a gap in oncoming traffic he immediately started to speed up, again stressing his back, and the LEDs increases further from two to three. Later, he was very explicit when explaining how it is more important for him to overtake, than worry about posture when in busy traffic. He went on to mention how he would sit in the right posture, if there were no traffic. This statement however, was contradicted by our video observations showing how after seeing a clear stretch of road with no traffic, he did not slow down and sit with back straightened. Instead he accelerated till he got close to the car ahead, and 4 LEDs lit up. When he was showed this video, he commented that if he had known for how long he was sitting in a bad posture, and how he was doing on making it to his destination on time, he would have adjusted his posture. Future sketching and in-situ enactments with a modified ReRide system making available the data the rider asked for will have to show whether this is the case or not.

All together, these observations, further emphasizes to us, that any design seeking to enable preventive measures for self-care as part of riding needs to present itself as subtle and suggestive, but by no means demanding or directive, if they are to be considered relevant by the riders in the first place.

"Vibration May Help, But I Will Have to Learn to Drive With It".

Also during the post-ride interview with riders the idea of having of non-visual cues of back posture made manifest by means of haptic and audio was brought forward.

One rider in particular suggested that non-visual presentation would be helpful for her. She was quite experienced in navigating the traffic, as she was a rider for 20 years. She never looked at her speedometer, which by the way, had stopped working. However, she was a very cautious rider, anticipating bumps and potholes well in time to slow down and correct her posture immediately after she hit a speed-breaker. She kept glancing at the display before correcting her posture. During the discussion she mentioned that even though she hardly looks at the dashboard when riding, she did look this time, as she wanted to know her lower-back posture. As part of the study we did not insist that the riders look at the display, but we had explained that it displays the data about lower-back posture, which may have influenced her actions.

She mentioned how over time she would stop looking at the display, as she will develop a habit of adjusting her posture whenever she slows down. Further she mentioned that an on-body haptic feedback maybe better to develop such a habit. However, when asked if such a display would disturb her riding experience, she mentioned that it might initially, but over time she will have to learn to ride with it. We take these suggestions as an important indication that we should work on broadening the notion of 'glanceability' to make cues available by means other than visual display.

Concluding Remarks

We engaged in an open-ended exploration of the idea of making back posture data available as visual cues to motorbike riders in order to encourage them to do in-situ adjustments of their lower back while riding to prevent lower-back injuries.

Using our ReRide interactive soft&hardware sketch we asked four riders to go for a ride and experience first hand what it is like to engage with data on their lower-back posture while riding. In subsequent interviews we asked the riders to reflect on their experience and through this bring forward suggestions for where to take the design of a ReRide system. Overall, we got promising feedback from the riders encouraging us to further explore the design of digital technology in support of preventive basic lower-back exercising while riding. In particular, all the four riders mentioned the importance of having access to lower back information while riding, while offering suggestions for future directions the work could take. As such, our interactive sketches successfully made it possible for the riders to directly engage as co-explorers based on actual experience rather than de-contextualized speculations on what it might be like to ride with systems the like of ReRide.

The riders' experience & feedback brought forward two concrete suggestions both pointing out the need to prioritize concerns for a healthy riding position with concerns for safe and effective driving. Based on these suggestions we will start exploring how to present real-time lower-back posture data in combination with data on the duration spent in an unfavorable posture and the estimated time left to reach the destination. Further, we will explore the use of alternative modalities in the interaction with posture data looking emphasizing that such an exploration clearly need to also focus on how the riders could learn to ride with such systems, without compromising the safety and ability to navigate traffic. Beyond an immediate response to the four riders, we are currently expanding our initial design exploration to 1) Include more sensor data acquired through a Bluetooth based personal area network of pressure and movement sensors. Some wearable and some integrated with the bike. 2) Integrate data on bike and rider condition in one and the same display space. 3) Build on a cloud-based Internet-of-Things architecture (e.g. Amazon Web Services IoT) where data generated across rides and riders are accumulated, analyzed and made available for inspection to riders before and after the rides across personal devices.

Finally, our work on ReRide demonstrated to us that the theoretical construct of embodied self-monitoring can be successfully transferred as a generative design ideal in support of people turning mundane activities of everyday life into opportunities for preventive self-care.

Figure 1 :

 1 Figure 1: Riding in Traffic

Figure 2 :

 2 Figure 2: Recommended Preventive Self-care Exercises for the Motorbike Riders 1

Figure 3 :

 3 Figure 3: ReRide Interactive Sketch. Rider with the belt. The display next to speedometer

Figure 4 :

 4 Figure 4: Riding with the ReRide display positioned as part of the existing dashboard

From: http://www.bmf.co.uk/news/show/7-tips-to-reduce-motorcycle-pain

Acknowledgements

We thank the four riders who spent time exploring the idea with us.


George E Raptis
email: raptisg@upnet.gr

Christina Katsini
email: katsinic@upnet.gr

Christos Fidas
email: fidas@upatras.gr

Nikolaos Avouris
email: avouris@upatras.gr

Effects of Image-Based Rendering and Reconstruction on Game Developers Efficiency, Game Performance, and Gaming Experience

Keywords: evaluation study, video games, image-based rendering and reconstruction, game development efficiency, game performance, gaming experience

Image-based rendering and reconstruction (IBR) approaches minimize time and costs to develop video-game assets, aiming to assist small game studios and indie game developers survive in the competitive video-game industry. To further investigate the interplay of IBR on developers' efficiency, game performance, and players' gaming experience we conducted two evaluation studies: a comparative, ecologically valid study with professional game developers who created games with and without an IBR-based game development pipeline, and a user study, based on eye-tracking and A/B testing, with gamers who played the developed games. The analysis of the results indicates that IBR tools provide a credible solution for creating low cost video game assets in short time, sacrificing game performance though. From a player's perspective, we note that the IBR approach influenced players' preference and gaming experience within contexts of varying levels of player's visual intersections related to the IBR-created game assets.

Introduction

The video game industry is continuously growing with revenue over $90 billion worldwide [START_REF] Newzoo | Top 100 Countries by 2015 Game Revenues[END_REF][START_REF]Essential Facts about the Computer and Video Game Industry[END_REF]. Thousands of people worldwide work on creating video games for entertainment, as well as for education, business and art [START_REF] Fuchs | The video game industry: Formation, present state, and future[END_REF]. The video game market is very competitive, with an increasing demand for sophisticated and more realistic games. Such requirements are barrier for small game studios and indie developers, as they need more resources, in terms of cost, time, expertise, and technology, to keep up with the competition. Therefore, small game studios and indie developers struggle to survive, and this has a direct negative consequence on the video game industry and the economy, as these developers bring in creativity and innovation.

One way to overcome this, is to introduce novel cost-effective technologies which are primarily based on image [START_REF] Ackermann | Photometric stereo for outdoor webcams[END_REF][START_REF] Laffont | Rich intrinsic image decomposition of outdoor scenes from multiple views[END_REF][START_REF] Chaurasia | Depth synthesis and local warps for plausible image-based navigation[END_REF][START_REF] Goesele | Ambient point clouds for view interpolation[END_REF] and video [START_REF] Tompkin | Videoscapes: Exploring Sparse, Unstructured Video Collections[END_REF][START_REF] Lipski | Virtual video camera: Image-based viewpoint navigation through space and time[END_REF][START_REF] Ballan | Unstructured Video-Based Rendering: Interactive Exploration of Casually Captured Videos[END_REF][START_REF] Levieux | Interactive viewpoint video textures[END_REF] reconstruction techniques. The users of such techniques can capture real-life scenes and objects with conventional apparatus (e.g., smartphones, photo cameras). The captured images/videos are then used to build the 3D realistic models of assets. Image-based reconstruction (IBR) seems to produce better results [START_REF] Starck | Objective Quality Assessment in Free-Viewpoint Video Production[END_REF].

Motivation and research question. Although it is known that IBR and photogrammetric methods provide a short-cut for creating 3D assets for video-games development [START_REF] Ackermann | Photometric stereo for outdoor webcams[END_REF][START_REF] Laffont | Rich intrinsic image decomposition of outdoor scenes from multiple views[END_REF][START_REF] Chaurasia | Depth synthesis and local warps for plausible image-based navigation[END_REF][START_REF]Capturing Reality[END_REF][START_REF]Meerstone Archa eological Consultancy: 3D Modelling with AgiSoft PhotoScan -Tests to determine the suitability of AgiSoft PhotoScan for archaeological recording[END_REF][START_REF] Raof | Three dimensional modeling of archaeological artifact using photomodeler scanner[END_REF], to the authors' knowledge, there is no thorough ecological study involving different stakeholders (game developers and game players) and investigating the interplay of a state-of-the-art IBR game development pipeline on game developers' efficiency, game performance, and gaming experience. In the context of the reported study a fully integrated research-based state-of-the-art pipeline for games development bootstrapped to game developers' requirements [START_REF] Fidas | Requirements Elicitation for new Video Game Development Tools : A Case Study[END_REF] was used.

Hence, the research questions investigated in this paper are: a) to explore the effects of games created with IBR on game developers' efficiency, in terms of time required to create video-games by also considering game performance metrics (game size, loading time, and scalability), and b) to explore the effects of games created with IBR on gaming experience, in terms of gamers' preference and graphics quality.

2

Method of Study

Procedure

We conducted two user studies: a) a comparative evaluation study during which video game prototypes were developed with the traditional vs. IBR methods aiming to gather quantitative and qualitative feedback related to efficiency and performance measures, and b) an eye-tracking A/B testing study with gamers playing the game prototypes created during the comparative evaluation study.

Comparative study of creating game assets with and without IBR. For this study, two professional game developers participated and developed two different games over a period of six months (May to October 2016). The participants developed their games within their own working conditions (i.e., ecologically valid conditions), without the intervention or help of our research team. They were asked to keep track of their activities and the time needed to perform the necessary tasks, adopting an activity diary-log approach. We provided them with a diary template. Moreover, several semi-structured interviews were conducted during and after the game development phase.

Comparative study of playing games created with and without IBR. For this in-lab study twelve gamers were recruited (5 females, 7 males), aged 20-32, and played different versions of the games created with the traditional and the IBR approach. They were recruited through email invitations, and they were undergraduate and postgraduate university students. All individuals were experienced gamers, playing video games more than twelve hours per week, and they had never played any of the games used in the study before. After the recruitment of the participants, twelve in-lab sessions were scheduled (i.e., one for each participant). In each session, the participant was asked to play the four game versions, wearing the eye-tracking apparatus. To avoid bias effects, six gamers played first the one game, and the other six played the other game first. In both groups, three participants played the traditional version first, and the rest three played the IBR version first. After the play-session, each participant was asked to fill a user experience questionnaire. Finally, each participant was asked to provide feedback and comments on their gaming experience through an unstructured interview. The participants were not informed that the two versions were developed using different technologies until the end of the interview.

Instruments and Apparatus

IBR-based game development integrated pipeline. The IBR pipeline used in our study was the CR-PLAY environment [START_REF][END_REF][START_REF] Cayon | A Bayesian Approach for Selective Image-Based Rendering Using Superpixels[END_REF][START_REF] Fuhrmann | Floating scale surface reconstruction[END_REF][START_REF] Gryka | Learning to Remove Soft Shadows[END_REF][START_REF] Langguth | Guided Capturing of Multi-view Stereo Datasets[END_REF]. CR-PLAY is a state-of-the-art mixed pipeline for creating game assets and integrating them in the game development workflow, using IBR techniques [START_REF] Cayon | A Bayesian Approach for Selective Image-Based Rendering Using Superpixels[END_REF][START_REF] Fuhrmann | MVE-An image-based reconstruction environment[END_REF]. CR-PLAY users follow a three-step approach to build a game asset: a) capture real-life objects (e.g., a building) by taking a sequence of photos from multiple angles; b) reconstruct them as 3D point cloud models; c) and import them into their standard game development workflow.

The games. Two video-games were created and played in our studies: Survive the Weekend and Basketball Stars. Survive the Weekend is a hidden object game in which the player is asked to find a number of items in a play-room within a given time. Basketball Stars is a first-person sport shooting game, and the players' goal is to shoot as many baskets as possible in a predefined amount of time against an opponent. The two games have a different intersection between the game assets and the game play in terms of visual search and visual attention, as Survive the Weekend requires constant visual attention of players through the whole scene, because they are searching for the hidden items; while Basketball Stars requires players' attention on specific game assets.

Apparatus: Game developers used their own computer systems to develop the games. Gamers played the games on a desktop computer (with Intel Core i7-4500U at 2.40GHz, and 8GB RAM). The screen used was the LG 22MP48D, at a screen resolution of 1920x1080 pixels. To investigate the participants' visual behavior, Tobii Pro Glasses 2 were used to record their eye movement patterns.

Gaming experience questionnaire. To measure gaming experience, we used the Immersive Experience Questionnaire (IEQ) [START_REF] Jennett | Measuring and defining the experience of immersion in games[END_REF]. IEQ is a credible and highly validated tool to evaluate players' experience [START_REF] Denisova | The Convergence of Player Experience Questionnaires[END_REF][START_REF] Nordin | Too Many Questionnaires: Measuring Player Experience Whilst Playing Digital Games[END_REF]. It consists of 31 questions of Likert type, including questions about graphics quality.

Results

Effects of IBR on game developers efficiency in creating video-game assets

The development of a game prototype with IBR took approximately 12 man-hours, regardless of the complexity of the scene. However, the time needed to develop a game prototype with the traditional approach was highly dependent on the number of assets to be included in the game, their complexity, and whether they have been used in other projects or were available from third-party providers. In our case study, the game developers were free to re-use any game asset and/or use third-party assets, as they would normally do, strengthening the ecological validity of the study. To create a game based on a simple scene with few items (N = 3), approximately 26 man-hours were required, while for a game based on a complex scene with many items (N = 19), 160 man-hours were required. In both cases, the developers required less time to create the IBR version.

The interviews revealed that IBR reversed the process the game developers followed to develop a game, as the IBR game scenario was based on the reconstructed scene, while traditionally they created the scenes based on the scenario.

Survive the Weekend Basketball Stars

Fig. 1. Game developers created the IBR game versions in less time than the traditional game versions, in both complexity levels.

Effects of IBR on game performance (size, loading-time, and scalability).

Game performance is a multidimensional variable, which can be measured on game file-size, loading-time, and scalability. In terms of file-size, the executable was bigger for the IBR versions (300MB for a simple scene, and 330MB for a complex scene) compared to the traditional versions (15MB for a simple scene, 20MB for a complex scene). The loading times were in-line with the file-size findings, and they were increased for the IBR versions (10 seconds for a simple scene, 20 seconds for a complex scene) compared to the traditional versions (2 seconds for both a simple and a complex scene). The aforementioned results reflect on the scene complexity and the size of point cloud models, introduced in IBR. Therefore, this has an impact on the scalability of a game, as developers could not build many levels. Fig. 2. IBR games were bigger in size than the traditional versions for both simple and complex scenes (left). IBR games had also longer loading times than the traditional versions for both simple and complex scenes (right).

Effects of IBR on gaming experience

Effects of IBR on game players' preference. The game players were asked to state which version they preferred: IBR or traditional. Ten participants stated that they preferred the traditional version of Survive the Weekend, a significant difference according to binomial statistical test (p = .019). In contrary, eleven participants stated that they preferred the IBR version of Basketball Stars, a significant difference according to the binomial statistical test (p = .003). When playing the IBR version of Survive the Weekend, the participants had to explore the whole scene to find and collect the hidden items, and they stated that most of the game elements were blurry when they were navigating through the scene. They also stated that many objects were not naturally placed and lighted in the scene. On the other hand, the Basketball Stars scene was more static, as the players could not navigate through the scene. Therefore, no blurring objects were noticed in the IBR version, and the participants found it to be more photorealistic, with smooth transitions and nice interaction.

Graphics quality. To measure how much the players valued the graphics quality, we conducted an independent-samples t-test for each game, with the technology factor (traditional and IBR) as the independent variable, and the graphics quality score (calculated using IEQ) as the dependent variable. In both tests, the assumptions were met. Regarding the Survive the Weekend game, the participants preferred the graphics of the traditional version (5.11 ± 1.48 vs. 4.01 ± 1.42, p = .046). Regarding the Basketball Stars game, the participants preferred the graphics of the IBR version (5.09 ± 1.34 vs. 4.32 ± 1.17, p = .042). This was also reflected on the overall immersion score, as the participants were more immersed when playing the traditional version of Survive the Weekend Eye-tracking analysis. The eye-tracking analysis verified the aforementioned finding, as the participants fixated many times and for long time periods on the whole backdrop scene, visually scanning for the hidden objects, in both versions of Survive the Weekend. On the other hand, they fixated intensively in specific areas of interest (i.e., basket, shooter, power bar) when playing Basketball Stars, as their goals was to shoot and score. The heat-maps of both versions of both games are depicted in Fig. 4.

4

Findings and Discussion

The findings of our studies are summarized into three categories: a) efficient creation of game assets with IBR, b) the bottleneck in performance when using IBR, and c) effective use of IBR depends on game type (Table 1).

Efficient creation of game assets with IBR. The IBR technology provided a faster method to create photorealistic game assets in comparison to the traditional approach (Fig. 1). The main benefit for the game developers is that IBR time to delivery is independent of the assets complexity, as our study indicated that the asset creation times were similar for creating games of varying game elements complexity.

The bottleneck in performance when using IBR. In the presented study, the game performance reflects on the executable file-size, the loading time, and the scalability of the game. In both games, the IBR versions were bigger in size, had longer loading periods, and were less scalable than the traditional ones (Fig. 2). Despite the fact that some of the aforementioned issues are technology-related and can be resolved (e.g., reduce file-size by incorporating sophisticated image compression algorithms), the IBR game performance will remain poor since game assets are not based on polygons. Game developers can create gamers quickly when they use IBR, but the game performance (in terms of file-size, loading time, and scalability) is a bottleneck.

Game genre affects preference of IBR video-games. Game players preferred the graphics quality of traditional Survive the Weekend (i.e., a game with heavy interaction with assets throughout the scene) than the graphics of the IBR version; and the graphics of IBR Basketball Stars (i.e., a game with light interaction with the scene), than the graphics of the traditional version. This was also reflected on their answers when they were asked explicitly which of the two versions (traditional or IBR) they preferred.

Games that require players to interact with the largest part of the scene or with most of the game assets (e.g., hidden objects games) require high visual attention. Therefore, as users visually explore the game environment, they can detect IBR-related flaws (e.g., bad lightning, non-normal position of an object, blurred assets), which influence their gaming experience (Fig. 3). On the other hand, when the players are engaged with a video game with more static scenes (e.g., point-and-click games), visually focusing on specific areas of the scene, they typically do not detect IBR-related flaws, and they enjoy the game more, as it is more realistic and aesthetically pleasant (Fig. 3).

Our eye-tracking analysis reflects on this finding (Fig. 4), as the players tend to fixate on various spots of the visual scene evenly, when playing a visual search game. On the other hand, their fixations are more intense and focused on specific areas of interest (e.g., the game assets they interact with) when playing games which use the background scenes to provide a more photorealistic perception, but they are not part of the gameplay or the players are not required to interact with them. Overall, the effect of IBR on gaming experience depends on the game type and the degree of the visual search activity (e.g., traditional methods will be preferred for games with heavy visual search, while IBR will be preferred for games with lighter visual interaction).

Metric Finding

Developers' Efficiency

IBR provided a faster approach for creating video-game objects, for both simple and complex scenes. However, traditional approaches can be considered for simple scenes.

Gaming Performance

Traditional approach outperformed IBR in terms of file size, loading times, and scalability. IBR games scenes and objects were bigger in size, had increased loading times, and were less scalable.

Gaming Experience

The game type plays an important role on the effective use of IBR.

Gaming experience was better for traditional games which require heavy visual interaction with the game assets and the scene (e.g., hidden-objects games). However, gaming experience was better for IBR games which require light visual interaction effect with the game scene (e.g., point-and-click at a static target), as they provide a more photorealistic environment.

Table 1. The main findings of our studies on developers' efficiency, gaming performance and gaming experience

Limitations and future work

The main limitation of our work is the relatively small sample sizes used in our studies. However, the statistical tests performed met all the required assumptions, providing credible results. Another limitation is the use of a research, but state-of-the-art IBR game development pipeline (CR-PLAY). As a future work, we will engage more endusers to evaluate the quality of the produced game elements and measure the gaming experience on games of varying types and characteristics.

Conclusion

In this paper, we investigated, through two evaluation studies, the impact of imagebased rendering and reconstruction (IBR) on game developers efficiency, games performance and game players' experience. In the first study, we engaged two professional game developers who created, during a six-month period and within ecologically valid conditions, two versions (traditional and IBR) of two different games. In the second study, twelve experienced gamers played the four game versions in the context of an in-lab, A/B testing, eye-tracking approach. The analysis of the results revealed benefits of the IBR approach, such as reduced time and costs for creating photorealistic game assets. Drawbacks were also revealed, such as increased loading times, huge file sizes of deployed games and scalability issues which can be credited to the very nature of the IBR technology. Regarding, the players' gaming experience, the analysis of the results revealed mixed outcome regarding players' preference of games created with the traditional vs. IBR approach which should be further investigated.

( 4 .Fig. 3 .

 43 Fig. 3. Gamers liked more the graphics of the traditional version of Survive the Weekend, and the graphics of the IBR version of Basketball Stars (left); Study participants preferred the traditional version of the visual-search games (e.g., Survive the Weekend), and the IBR version of the point-and-shoot games (e.g., Basketball Stars).

Fig. 4 .

 4 Fig. 4. The participants visually interacted with the whole scene when playing Survive the Weekend; but, they visually focused on specific areas of interest when playing Basketball Stars.


Jeffrey C F Ho
email: jeffreycfho@gmail.com

Practice in Reality for Virtual Reality Games: Making Players Familiar and Confident with a Game

Game designers include training levels in video games to prepare players so that they can enjoy the game. The training levels of virtual reality (VR) games are typically assumed to be within the virtual world of the game. New players must learn about a new game in such an unfamiliar virtual world. A tutorial in the real world offers a potential way to enable players to learn about a new game and to practice the skills in a familiar world. To explore any effects of a real-world tutorial in VR games, an experiment was conducted, the results of which show that a real-world tutorial is effective in helping new players feel confident about and familiar with a VR game before playing it. However, it is not as effective as virtual-world tutorial in increasing game performance.

Introduction

Virtual reality (VR) headsets have become popular in recent years. VR technologies enable game designers to explore new forms of gameplay. Many players may be new to VR games and may require assistance in getting familiar with virtual environments and gaining basic skills. Therefore, game designers design tutorials in video games to prepare new players for a game.

Unique challenges arise when designing tutorials for VR games. Video game tutorials are typically presented within the video game environment. If the same approach is used in VR games, the tutorials would be presented in a VR environment that is new in every VR game. Players must wear a VR headset and fully immersed in an unfamiliar environment while simultaneously acquiring basic skills for the game. This is similar to someone new to basketball preparing for a basketball match that will be played on an unfamiliar court. Receiving training in the court may be helpful; however, he or she may feel more comfortable receiving basic training in a familiar place (e.g., his or her own backyard). In VR games, whether players can receive basic tutorials in a familiar place (e.g., their own living room) instead of the unfamiliar virtual environment of a VR game should be considered. This paper focuses on real-world tutorials for VR games.

Tutorials in the real world can help new players learn how to play a game. In the real world, designers can replicate certain objects (e.g., tools) from VR games. Such objects provide new players with an opportunity to experience the settings and interactions in a manner similar to that in the VR game. Thus, players can learn about a new game in a familiar, real setting while acquiring some basic skills on how the game is played. Then, when they start playing a VR game, they can feel familiar with the game mechanics and achieve goals with the basic skills that they have acquired. This raises a concern of whether real-world tutorials can fulfill two purposes of game tutorials: 1) letting new players become familiar with the game, and 2) allowing them to acquire the necessary skills to play.

Tutorials in the real world provide opportunities for players to familiarize themselves with a new VR game because they are given in a familiar setting. Full immersion into the virtual world is not required until the players are prepared and start playing the VR game.

Another purpose of in-game tutorial is the acquisition of basic skills. An obvious concern about transferring game tutorials to the real world is whether the skills acquired in reality can be transferred to a VR world. VR simulation training for real-world tasks has become a common approach in training in many applications (e.g., military and aviation training). This suggests that skills can be transferred between virtual and real worlds. In other words, skills acquired in the real world are potentially transferable to a virtual world.

Real-world tutorials for VR games have practical benefits in certain applications. In most public VR public installations, such as those in shopping malls, few VR devices are available for people to use. Moreover, people must queue for a long time, yet they are typically allowed to enjoy the installation for only a few minutes. Tutorials in the real world would allow participants to practice while waiting and thus ensure that they are ready when it is their turn to play the VR applications.

This approach involves players' participation in two realities. The tutorial is given in a familiar setting (the real world) but the actual gameplay occurs in a virtual world. The research question in the present study thus concerns whether and how a tutorial in reality is effective in aiding new players with becoming familiar with and acquiring basic skills for playing a VR game.

Related Work

Tutorials and Practice in Video Games

A tutorial is a common feature in video games. A tutorial prepares players for gameplay by providing instructions and letting the players practice. The players' abilities must match the challenges in the game so that they can enjoy it [START_REF] Csikszentmihalyi | Flow: The psychology of optimal experience[END_REF]. If a tutorial is not available, new players can start with the first or second levels. However, players may spend their attention experimenting and developing skills during their gameplay in the initial levels instead of engaging themselves in the game content (e.g., narratives, visual aesthetics). Tutorials provide an opportunity for new players with limited ability to gain knowledge and ability before playing the main part of a game. Practice in the tutorial provides the same mechanism as the game, but with fewer constraints, such as the absence of a time limit. Examples include Tom Clancy's Splinter Cell (2002) and Portal 2 (2011).

Tutorials have different formats. Some tutorials are aimed at providing information to new players. Tutorials that are mainly based on images and text can engage players in relatively complicated games [START_REF] Andersen | The impact of tutorials on games of varying complexity[END_REF]. Players may be able to learn how to play a game through experimentation [START_REF] Iacovides | Player strategies: Achieving Breakthroughs and Progressing in Single-player and Cooperative Games[END_REF].

When players play a VR game, they must become familiar with the virtual environment and how to use tools (e.g., shotguns) to interact with objects in the virtual world (e.g., shooting zombies). Practice-based tutorials may assist in overcoming this problem. Through practice, players can become accustomed to a tool, hold it, and use it as an extension of their body. Moreover, knowing the rules and tasks of a VR game is insufficient (e.g., an information-driven tutorial based on images and text); new players must be given an opportunity to actually practice using the tools (e.g., weapons in a game) to face challenges they encounter in the game (e.g., killing zombies).

A typical approach involves designing a training sequence in a VR game that enables players to experience the game before enjoying the main game content. This means that practice occurs in the virtual environment, which is new and unique in every VR game.

Influences Between Reality and Virtual Reality

Researchers in various disciplines have examined the relationship between experiences in real and virtual worlds. In human-computer interaction (HCI), researchers have explored training in a virtual environment with virtual human influence behavior in the real world [START_REF] Chollet | An interactive virtual audience platform for public speaking training[END_REF], [START_REF] Chollet | Exploring feedback strategies to improve public speaking: an interactive virtual audience framework[END_REF], [START_REF] Jones | Expressing social attitudes in virtual agents for social coaching[END_REF]. For example, Chollet et al. [START_REF] Chollet | An interactive virtual audience platform for public speaking training[END_REF], [START_REF] Chollet | Exploring feedback strategies to improve public speaking: an interactive virtual audience framework[END_REF] used a virtual audience to train people in public speaking skills. In their user studies, they found that training with a virtual audience can improve trainees' public speaking skills. Trainees were also found to have improved eye contact and fewer unnecessary pause fillers in their talks.

In media studies, researchers have investigated the effects of media content on audiences' behavior in the real world. One research focus concerns whether and how violence in video games influences children's and adolescents' behavior [START_REF] Anderson | Violent Video Game Effects on Children and Adolescents[END_REF]. The relevant findings have implications on policymaking and regulation. Such an influence can be perceptual to some gamers, rather than being behavioral. Ortiz de Gortari et al. [START_REF] Ortiz De Gortari | Game Transfer Phenomena in Video Game Playing[END_REF] interviewed gamers and found that some of them experienced difficulties in the perception of real-life events, elicitation of automatic thoughts, sensory perceptions, and dissociative experiences. This is called the game transfer phenomenon.

Most previous studies examining the relationship between experiences in the virtual world and the real world have mainly focused on the effect of the virtual world on experiences and behavior in reality, but not the converse. One exception is a study by Ho [START_REF] Ho | Effect of Real-World Experience on Immersion in Virtual Reality Games: A Preliminary Study[END_REF], who investigated the influence of real-world experiences on immersive experiences in the virtual world. The result suggests that the experience of a game in the real world causes experienced players to become more immersed in the VR game simulating it. The effect on inexperienced players is the opposite. However, the statistical result was not sufficiently strong to be conclusive.

One research area that evidently shows influences of VR on the real world is simulation training in motor learning literature, which is reviewed below.

Motor Skills and Practice

Playing VR games often involves some motor skills such as turning the head to inspect the environment and avoid obstacles. Thus, practice for VR games can be considered a type of motor skill training. According to research on motor learning [START_REF] Schmidt | Motor Learning and Performance: From Principles to Application[END_REF], a skill is any ability that facilitates task completion with maximum certainty and minimum costs. Costs involves physical and mental energy as well as time. All skills comprise three elements: perception of the environment, decisions of what muscular actions to perform (and when to perform them), and the actual execution of such actions to achieve a goal.

Practice is the most crucial activity in learning a motor skill [27, p. 199]. A primary goal of practice is for learners to acquire a skill. They can improve their abilities to selectively perceive information that is crucial to achieving a goal and detect errors by themselves. Through the process of practicing, they can also reduce the amount of attention required to complete a task.

Another crucial goal of practice is skill transfer (also known as skill generalization), which refers to the concept that skills acquired from practice or experience with one task can be applied to another task. Learners are expected to transfer their skills from practice scenarios to novel scenarios that they have not encountered before. The transfer of a skill is referred to as positive if the skill is enhanced by practice but negative if the skill is reduced.

The degree of transfer depends on the similarity between the practice task and a target task [START_REF] Schmidt | Motor Learning and Performance: From Principles to Application[END_REF]. The similarity between tasks can be decomposed into three aspects: (1) fundamental movement pattern, (2) perceptual elements, and (3) strategic and conceptual similarities. Fundamental movement patterns refer to the movement patterns involved in a task. If the fundamental movement pattern (e.g., arm movement in throwing a baseball) of practice and actual tasks are similar, skill transfer are likely to be successful. Moreover, if the perceptual cues involved in a practice task (e.g., perceiving a ball trajectory) are similar to those in the actual task, learners can react appropriately to different situations and thus the skill can be transferred. Skill transfer also depends on the similarity of strategic and conceptual elements. Different activities can have similar rules, strategies, guidelines, and concepts. For example, the similarity in road rules between commonwealth countries assists tourists from one commonwealth country when traveling in another commonwealth country, but this may cause a negative transfer effect if they travel to North America, where the road rules are different.

One application area that depends on the principles of skill transfer is simulation practice. A simulator is a device that replicates the features of a real-world target task in a virtual environment. Simulator training can be essential in situations where training with real-world tasks is expensive, when facilities are limited, or where practice in the real world is not feasible (e.g., surgery).

Researchers on training simulations have examined whether the skills acquired in VR training for serious tasks can be effectively transferred to the real world. Gallagher et al. [START_REF] Gallagher | Prospective, Randomized Assessment of Transfer of Training (ToT) and Transfer Effectiveness Ratio (TER) of Virtual Reality Simulation Training for Laparoscopic Skill Acquisition[END_REF] conducted two studies that involved surgical training-one in a VR simulation environment and one in the real world. They found that VR simulation improved skill levels in the real world, regardless of the level of previous experience of the trainees. Similar studies on the effects of training in a virtual simulation environment have also been conducted in military and aviation training [START_REF] Bell | Evaluating the Effectiveness of Flight Simulators for Training Combat Skills: A Review[END_REF], [START_REF] De Winter | Training Effectiveness of Whole Body Flight Simulator Motion: A Comprehensive Meta-Analysis[END_REF].

If the quality of a simulation is high, skill transfer to real-world application is expected to be effective. In the discussion of quality of simulation, two types of fidelity are concerned [START_REF] Kozlowski | A Psychological Fidelity Approach to Simulation-based Training: Theory, Research, and Principles[END_REF]. Physical fidelity refers to the extent to which the surface features (e.g., audiovisual elements) of a simulation and the target task are replicated. Psychological fidelity refers to the extent to which a simulation can produce behaviors and processes required for a target task. This type of fidelity is more concerned with the skills and behaviors required to perform a target task. The two types of fidelity should be complementary to each other.

Methodology of Studying Digital Games

An experiment is a standard research method in digital games (such as [START_REF] Cairns | Who but not where: The effect of social play on immersion in digital games[END_REF], [START_REF] Cairns | Immersion in Digital Games: Review of Gaming Experience Research[END_REF], [START_REF] Depping | Trust Me: Social Games are Better than Social Icebreakers at Building Trust[END_REF]). Researchers use this method for studying very specific aspects [START_REF] Cairns | Research Methods for Human-Computer Interaction[END_REF]. It is often done in a relatively controlled environment and carefully manipulate specific aspects of the stimulus (i.e. a game in game research). Researchers either select an existing game and modify the settings (e.g., [START_REF] Cairns | Who but not where: The effect of social play on immersion in digital games[END_REF], [START_REF] Iacovides | Removing the HUD: The Impact of Non-Diegetic Game Elements and Expertise on Player Involvement[END_REF], [START_REF] Denisova | First Person vs. Third Person Perspective in Digital Games[END_REF]) or custom make their own game to suit specific purposes (e.g., [START_REF] Depping | Trust Me: Social Games are Better than Social Icebreakers at Building Trust[END_REF] , [START_REF] Depping | How Disclosing Skill Assistance Affects Play Experience in a Multiplayer First-Person Shooter Game[END_REF], [START_REF] Gutwin | Does Helping Hurt? Aiming Assistance and Skill Development in a First-Person Shooter Game[END_REF]). In some cases, a custom-made game can be relatively simple such that one specific aspect can be focused in a study. For example, Depping and his colleagues ( [START_REF] Depping | Trust Me: Social Games are Better than Social Icebreakers at Building Trust[END_REF]) created a game called Labyrinth for their experiment aiming to study how players build trust in a game environment. Labyrinth was a 2-player game that requires cooperation to collect all the gems in a maze. The two players had different roles (so-called pusher and collector). They needed to communicate via voice chat to cooperate. The authors reported each pair of participants completed a round in 2 minutes. The game deliberately made simple such that they can be focused on how the challenges and cooperation in games can influence interpersonal trust. We took a similar approach in creating a simple game for our experiment.

Investigating Practice in Real World for VR Games

The real world is familiar to players and presents opportunities for practice sessions. On the basis of the perspectives covered in the previous section, the approach of realworld-based practice is analyzed in this section to examine its effectiveness in enhancing new players' confidence, familiarity, and skill learning. The research hypotheses are then proposed.

Practice in the real world provides a familiar environment for players to prepare themselves for a game. Players in a familiar environment may be more comfortable in learning about the mechanics of a game. As shown in previous research on and applications of simulation training, skills can be transferred from VR to the real world, which suggests that skills can be transferred between realities. Thus, real-world training for VR games should be effective as well.

Practicing in reality for VR games can involve tools and objects that replicate their counterparts in a VR game. Players can attempt challenges similar to those in the VR game. During practice, players can hold replicas of tools in the VR games, attach them to their bodies, and perform tasks similar to the challenges in the game. This attachment is considered a coupling process in the embodied interaction perspective [START_REF] Dourish | Where the action is: the foundations of embodied interaction[END_REF].

Practice in virtual worlds and the real world differ in their strengths and weaknesses. Practice in a virtual world may be more effective for skill learning and transfer because of the high level of physical and psychological fidelity in simulations. The audiovisual effects in a VR practice environment can replicate those in a VR game (physical fidelity). Basic game rules and mechanics that require new players to strategically think and behave in a manner similar to how they would in a VR game can also be replicated in VR practice (psychological fidelity). The drawback with this approach is that it requires new players to be immediately immersed in an unfamiliar virtual world that they must learn about. By contrast, practice in the real world may be limited in creating a simulation with a high level of physical fidelity because recreating the audiovisual effects used in VR games may be impractical in the real world. However, a certain level of psychological fidelity can be realized if the real-world practice requires new players to think and behave in a manner that is similar to what is required in a VR game.

From this viewpoint, the key questions of the present study concern whether the experience gained in reality can help new players in a VR game, and if so, whether such practice is better offered in the real world or within a VR game itself.

Can Real-World Practice Prepare Players?

Practice-based tutorials enable new payers to experience a game's gameplay. If the challenges and tools in the practice-based tutorial are consistent with those in the VR game, players can attempt to use the tools. This paper focuses on three aspects of gameplay: confidence in playing the game, familiarity with the game, and game performance. To facilitate answering this question, hypotheses were formulated.

Confidence. Confidence refers to the extent to which players believe they can perform well in the game. Psychologists refer to this concept as self-efficacy [START_REF] Terlecki | Sex Differences and Similarities in Video Game Experience, Preferences, and Self-Efficacy: Implications for the Gaming Industry[END_REF]. The focus involves preparing new players for a VR game and therefore their confidence after any practice and before actual gameplay. Practice in the real world should develop new players' confidence in a VR game as long as the challenges and tools in the VR game are replicated in the real world. Thus, the proposed hypothesis is as follows:

H1.1: New players who practice in the real world will feel more confident playing a VR game than those who do not have any practice.

Familiarity. Familiarity refers to the extent to which players are familiar with a game before they actually play it. Although it is a different reality from the virtual world, the real world is a familiar reality to the players; therefore, they may benefit from such practice.

H1.2: New players who practice in the real world will be more familiar with a VR game than those who do not have any practice.

Players' familiarity with a game can also be observed form their behavior. If players are familiar with a VR game, they should be prepared to start the game as soon as they affix a VR headset. Players who are less familiar with a VR game will require more time to prepare. H1.3: Once new players who practice in the real world enter a VR game, they will take less time to prepare and start the game than those who do not have any practice.

Game performance. Game performance refers to players' actual measurable performance in playing a VR game. Practice in reality can enable players to gain certain basic skills. Skills acquired in the real world should be transferrable to a virtual world provided that the real-world practice simulates the game rules and mechanics of a VR game with a high level of psychological fidelity. Therefore, real-world practice should be an effective form of practice for VR games. Thus, H1.4: New players who practice in the real world will perform better in a VR game than those who do not have any practice.

How Does Real-World Practice Compare with VR Practice?

The real world enables players to practice in a familiar reality. New players use tools with their body in the real world. By contrast, in VR practice, players must use tools in the virtual world with their characters' body in the virtual world using their own body and any game controllers in the real world.

Confidence. Practice in the real world enables players to face challenges in the VR game with concrete and realistic sensory-motor experience, similar to how they learn a new skill in their daily lives. However, the advantage of practice in the virtual world is that the players understand that they are practicing in the same world as that in which the actual gameplay takes place. The proposed hypothesis is as follows:

H2.1: New players who practice in the real world will feel more confident playing a VR game than those who practice in the virtual world.

Familiarity. In terms of familiarity that players can gain from practicing, the difference between real-world practice and VR practice is that the real world is a reality that new players are already familiar with. Arguably, players who receive practice in the real world should be aware that actual gameplay will occur in a different, virtual world. They might still be unfamiliar with the game after such practice. However, given that players understand that the challenges and tools are the same as those in the VR game, the concrete experience of touching these tools in the real world should provide them with a higher sense of familiarity.

H2.2: New players who practice in the real world will be more familiar with a VR game than those who practice in the virtual world.

The more familiar they are, the faster they can prepare once they enter the virtual environment. Following the same argument about familiarity, the following hypothesis is proposed: H2.3: Once new players who practice in the real world enter a VR game, they will take less time to prepare and start the game than those who practice in the virtual world.

Game Performance. Regarding game performance, the key focus concerns whether practice in the real world trains players more effectively than that in the virtual world. Compared to practice in the real world, practice in the virtual world of a VR game provides a high level of physical and psychological fidelity. Therefore, virtual-world practice should be more effective than real-world practice.

H2.4: New players who practice in the virtual world will perform better in a VR game than those who practice in the real world.

The first three hypotheses concern about confidence and familiarity while the forth hypothesis is about game performance. We argue that practice in the real world benefits new players better in terms of confidence and familiarity because the real world is where people acquire skills since birth. It should allow people to feel confident about and familiar with a task (playing a game in this case) that they are going to engage in. In contrast, game performance here is concerned about how well new players actually perform in a game. Regarding performance, practice in virtual world should benefit new players better because the virtual world is more similar to the environment where the game takes place than the real world. This is based on the literature in motor learning regarding the influence of similarity between training environment and task environment.

Study Design

To test the hypotheses, an experiment was designed and conducted. Practice was the independent variable, which resulted in three conditions: no practice (Control Condition), practice in reality (Reality Condition), and practice in VR (VR Condition). The effects of treatments in preparing players for a VR game were investigated. Specifically, four areas corresponding to the hypotheses were examined: confidence with the game, perceived familiarity with the game, initial exploration time and game performance. Confidence and perceived familiarity were measured using a survey question with a 7-point Likert scale. The initial exploration time was measured according to the time after participants wore a VR headset and before they indicated that they were ready to start the game.

Regarding measuring players' performance, there are many different choices (e.g., [START_REF] Loh | Predicting expert-novice performance as serious games analytics with objective-oriented and navigational action sequences[END_REF], [START_REF] Murias | The effects of video game use on performance in a virtual navigation task[END_REF]). Studies use different measures for different types of games [START_REF] Jentzsch | Correlation Between Arthroscopy Simulator and Video Game Performance: A Cross-Sectional Study of 30 Volunteers Comparing 2-and 3-Dimensional Video Games[END_REF]. In our custom-made game, the task was to put five balls into the target container. If they have the skill to transfer balls to the target, they should be able to do so efficiently. In this experiment, the purpose of measuring performance is to investigate the effect of skill transfer across different realities. The game performance was measured according to the time each player required to complete the game (possible score: 5 points).

Sixty participants (52 women) with different levels of gaming experience were recruited. Their ages ranged from 19 to 28 years (mean (M) = 21.6, standard deviation (SD) = 1.9). Among these participants, 51 had experience playing video games, which ranged from 4 to 18 years. All of them indicate they have zero years of experience in playing VR games.

The Game

A VR game called "Hospital On Fire" was designed for this experiment. In the game narrative, the player is trapped in a hospital that is on fire. The player must extinguish the fire by triggering water sprinklers. However, the player can only move his or her head. A spoon-like tool is attached to the player's head. The player must move his or her head to catch a ball from a dispenser on his or her left and then transfer the ball to a target container on his or her right. For every ball the player puts into the target container, a water sprinkler is triggered to extinguish a portion of the fire. To complete the game, the player must put five balls into the target container. The game was developed using Unity and Oculus Rift DK2. Screenshots of the game are shown in Fig. 1. Two types of practice were created for the game: practice in reality and practice in VR.

Practice in Reality

For practice in reality, a replica of the spoon-like tool was created (see Fig. 2). The tool was attached to a pair of goggles. A small plastic bucket was placed on the right-hand side of the participant and was used as a physical replica of the target container. A researcher stood on the left-hand side of the participant. During practice, the participant affixed the goggles (with the tool attached). Every time the participant turned left, a researcher placed a ball in the spoon-like tool. The participant was asked to practice transferring balls to the small plastic bucket. Each participant was given 1 min to practice.

Practice in VR

For practice in VR, a VR program was created (see Fig. 3). In the practice program, a spoon-like tool similar to that in the actual VR game was placed in front of the participant's face. The participant controlled the tool by moving his or her head. A target container and a ball dispenser were placed on the player's right-and left-hand sides, respectively. During practice, every time the player turned left, a ball was dispatched.

The participant was asked to transfer balls to the target container. Each participant was given 1 min to practice.

Procedure

Participants were randomly assigned to the three conditions. A total of 20 participants were included for each condition. When a participant arrived the laboratory, he or she was briefed and asked to read and sign a consent form. The participant then completed a questionnaire regarding background information, such as gender and age. A PDF document introducing the VR game was then shown to the participant. The introductory document presented the story, rules, and gameplay instructions with some screenshots.

Participants in the Reality Condition then practiced within the reality program. Participants in the VR Condition practiced with the VR practice program. Participants in the Control Condition did not have any practice. Before playing the VR game, participants were asked about their confidence and familiarity with the game. They then affixed the VR headset. The game did not start immediately. The participants were reminded to explore the game environment. When the participant was prepared, he or she told the researcher to start the game. The researcher then helped the participant start the game, and the participant began playing the VR game. When they finished the game, they removed the VR headset. Finally, they were debriefed.

(

Results

An analysis of variance (ANOVA) on the confidence before gameplay showed significant differences among the conditions (F(2, 57) = 7.40, p < .005, n 2 = . Confidence in the VR Condition was found to be higher than that in the Control Condition, with statistical significance (p < .05). Tukey's-b test for homogeneous subset was performed to examine if there are additional groupings among the conditions. The result is shown in Table 1. It shows that the Reality Condition and VR Condition statistically belong to the same group with a higher level of confidence, whereas the Control Condition belongs to its own group with lower confidence.

An ANOVA on the self-reported familiarity before gameplay indicated significant differences among the conditions (F(2, 57) = 8.08, p < .005, n 2 = .22). In the post-hoc analysis, the Bonferroni test showed that familiarity in the Reality Condition (M = 4.40, S.D. = 1.39) was significantly higher than (p < .005) that in the Control Condition (M = 2.81, S.D. = 1.27). This supports H1.2. No statistical difference was identified between the Reality Condition and the VR Condition (M = 4.25, S.D. = 1.37). This does not support H2.2. Familiarity in the VR Condition was found to be significantly higher than that in the Control Condition (p < .01). Tukey's-b test for homogeneous subsetoffered groupings is shown in Table 1. It shows that the Reality and VR Conditions statistically belong to the same group with higher familiarity, whereas the Control Condition belongs to its own group with lower familiarity.

An ANOVA on the exploration time showed significant differences among the conditions (F(2, 57) = 3.78, p < .05, n 2 =.12). In the post-hoc analysis, the Bonferroni test showed no statistical significance between the Control Condition (M = 20.55s, S.D. = 5.55s) and the Reality Condition (M = 20.00s, S.D. = 7.67s). Therefore, H1.3 is not supported. Exploration time in the VR Condition (M = 15.45s, S.D. = 6.03s) was found to be shorter than that in the Reality Condition, with marginal significance (p = .09). This does not support H2.3. Exploration time in the VR Condition was found to be significantly shorter than that in the Control Condition (p < .05). Tukey's-b test for homogeneous subset-offered groupings is shown in Table 1. It shows that the Control Condition and Reality Condition statistically belong to the same group, whereas the VR Condition belongs to its own group.

An ANOVA on the game performance showed significant differences among the conditions (F(2, 57) = 10.85, p < .001, n 2 =.28). In the post-hoc analysis, the Bonferroni test showed no statistical difference between the Control Condition (M = 65.30s, S.D. = 18.38s) and the Reality Condition (M = 53.75s, S.D. = 19.09s). Therefore, H1.4 is not supported. Game performance in the VR Condition (M = 38.75s, S.D. = 16.65s) was found to be significantly higher than that in the Reality Condition. Therefore, H2.4 was supported. Tukey's-b test for homogeneous subset-offered groupings is shown in Table 1. It shows that the No Practice and Practice variables in the Reality Condition statistically belong to the same group, whereas Practice in the VR Condition belongs to its own group. Table 2 shows a summary of the results.

Discussion

Real-World Practice is Effective in Increasing Confidence and Perceived Familiarity

Practice in reality helps players feel more confident and familiar with a VR game. This is in line with our earlier discussion regarding the potential benefits of practice in a familiar reality. This suggests that our common understanding about practicing can be applied to reality and VR: practicing in a familiar place increases confidence and familiarity with the challenge to be faced in an unfamiliar place. Even if the players have not played the VR game, practicing in a familiar reality makes them feel as confident and familiar as someone who has practiced in the VR (as reflected by the groupings shown in Table 1).

However, the results show that even if practice in reality helps new players feel more familiar with a VR game, they still require time to prepare for the game when they first enter it. Their actual familiarity with the game is similar to conditions that they have no practice. This suggests that their perception of familiarity differs from their actual familiarity. Practice in reality makes them feel that they are familiar with a VR game before playing it, whereas they are actually not that familiar with it. This enhancement in perceived familiarity can potentially encourage new players to try out a VR game for the first time, which is crucial in game design [START_REF] Cheung | The First Hour Experience: How the Initial Play Can Engage (or Lose) New[END_REF].

This also implies that the effects of practice-based practice can be multidimensional. Future research in practice should investigate the effects of practice in different aspects.

Practice in Reality vs. Practice in VR

Our study provides evidence of the effects of experience in the real world on experience in VR. The results show that practice in VR is more effective than practice in reality in terms of actual familiarity and game performance. Practice in reality and VR are equally effective in increasing new players' confidence and familiarity.

These results do not show that the skills acquired through reality-based practice is applicable in confronting the challenges in a VR game. The acquired skills was not shown to reduce players' performance in VR games in this study; in other words, no negative skill transfer was observed. The results suggest that player performance can be improved through practicing in the virtual environment of a VR game. This is consistent with the skill transfer principles. Similarity is a determinant of skill transfer between reality and VR. This raises a concern of whether skill transfer between realities can be effective. If every VR game had its own version of reality, the skills acquired in one VR game might not apply to other VR games.

The effect of practice in reality on confidence is as beneficial as that of practice in VR. This means that practice in the real world helps players to be confident, as if they have practiced in VR, whereas their game performance is as if they had no prior training. This interesting finding suggests that practice in reality is beneficial to players in emotional and motivational aspects. Further research on psychological effects of real world practice is warranted.

Practical Implications

To game designers, this opens new opportunities for practice design. As mentioned, VR games are relatively new in major markets. The first experience is crucial in retaining players [START_REF] Cheung | The First Hour Experience: How the Initial Play Can Engage (or Lose) New[END_REF]. Encouraging new players to try out a VR game is crucial for success. One possibility involves helping them feel confident and familiar with a new game before they purchase it. Therefore, they would not be apprehensive. This result suggests that designing the practice to be experienced in reality helps new players feel more confident and familiar with it. Such practice may encourage players who are new to a VR game or VR games in general to try one. For example, in public VR installations, practice or some experience in the real world might encourage people who are new to, or even afraid, of an unfamiliar VR environment to gain confidence and become familiar with that environment.

This points to a potential new direction for tutorial design. The present paper suggests that practice in reality improves players' perceptions of their own confidence and familiarity. Game designers can consider including practice in tutorials in the real world. They can also explore the advantages of the real world, such as tools with materials other than plastic (which is often the case with VR headsets and controllers).

Limitations

Similar to other studies, the present study is not without limitations. The game designed for the experiment was relatively simple; it contained only one challenge (transferring balls) and one level. A typical VR game may contain different types of challenges and multiple levels. The key in the present study is to investigate the relationships between practice in reality and gameplay experience in VR. The simplicity of the game enables the isolation of the two factors being concerned through a high degree of control in the experimental conditions. The result offers evidence to support a causal relationship in certain aspects of gameplay experience.

In the experiment, the majority of the participants were female. This may reduce the generalizability of the results. We would like to point out that the game used in the study did not show nor imply the gender of the player character. The experimental procedure did not involve any gender-specific materials. We would argue that the influence of gender, if any, on the results would be very limited. Future studies may examine if gender moderates effects of practice in reality.

In the present study, the tasks in practice are assumed to be identical to those in actual gameplay. This means that practice in reality can only cover tasks in VR games that can be replicated in the real world. Therefore, this limits the applicability of this approach to VR games that contain challenges not replicable in reality, such as magic spells and killing zombies. However, practice in reality can be emphasized in the challenges that can be made available in the real world. Future research should focus on the influence of practice in reality on virtual experience in areas not covered by the practice.

Conclusion

The experiment reported offers evidence to show that practice can help new players of VR games in certain aspects, even if the practice is performed in the real world. Future research is required to further investigate the influences of such practice in other aspects of gameplay experience. Nonetheless, the result suggests a new approach to tutorial design for game designers to consider.

Fig. 1

 1 Fig. 1 (a)-(f) Screenshots of steps to gain one point in the game

Fig. 2

 2 Fig. 2 (a) Equipment for practice in reality, (b) demonstration of wearing the goggles with the tool, and (c) demonstration of transferring a ball with the tool

Fig. 3 .

 3 Fig. 3. (a)-(f) Screenshots of steps in practice in VR.

  21). Bonferroni test was performed to examine how the conditions compare with each other. The Bonferroni test revealed that confidence in the Reality Condition (M = 4.75, S.D. = 1.45) was significantly higher (p < .005) than confidence in the Control Condition (M = 3.20, S.D. = 1.24). Therefore, H1.1 is supported. No significant difference was identified between the Reality Condition and VR Condition (M = 4.40, S.D. = 1.31). Therefore, H2.1 is not supported.

Table 1 .

 1 Result of Tukey's-b test for homogeneous subsets based on four dependent measures. Means and standard deviations (in brackets) of respective measurements of three groups are shown in the table cells

		Confidence	Perceived		Exploration	Performance
				Familiarity	Time
	Conditions	Subset	Subset	Subset	Subset	Subset	Subset	Subset	Subset
		1	2	1	2	1	2	1	2
	No Practice	3.20		2.85		20.6s		65.3s
		(1.24)		(1.27)		(5.55s)		(18.4s)
	Practice in Reality		4.75		4.40	20.0s		53.7s
			(1.45)		(1.39)	(7.57s)		(19.1s)
	Practice in VR		4.40		4.25		15.4s		38.7s
			(1.31)		(1.37)		(6.03s)		(16.7s)

Table 2 .

 2 Summary of results

	Question 1		Question 2
	Is practice in reality effec-	How does practice in reality
	tive?		compare with practice in
	Dependent Variables		VR?
	Confidence	H1.1^	H2.1
	Perceived Familiarity	H1.2^	H2.2
	Exploration Time	H1.3	H2.3
	(Actual Familiarity)
	Performance	H1.4	H2.4*
	^ supported with statistical significance (p<.005). * supported with statistical significance (p<.05).

Acknowledgements

We thank all the participants for their participation and all the reviewers who have read and given feedback on the earlier versions of the manuscript.