Keywords

1 Introduction

In recent years, head-mounted displays (HMD) have become widespread as systems that can be easily immersed in 3D space. Among them, games using HMD have also appeared. Various genres of games such as action games, shooting games, and games that reproduce sport have appeared. However most of these things simulate and experience only vision and hearing. In order to further improve the immersive feeling of HMD games and increase the breadth of experience, it is important to stimulate sensations other than vision and hearing. TACTSUIT [1] developed by bHaptics et al. has succeeded in stimulating the skin sensation using a vibrator and presenting the sensation of being touched or being shot with a gun. The system developed by Nippon Telegraph and Telephone Corporation [2] has succeeded in presenting the feeling of walking even while sitting by applying vibration stimulation to the sole. In everyday life, you may feel someone’s presence even without footsteps or touched sensations. This is thought to be due to the quasi-electrostatic field [3, 4] discovered by Takiguchi et al. In this paper, we propose a system that promotes the perception of the existence of objects according to the situation in 3D space, which has not been realized so far. In addition, when urging the perception of the existence of an object, the quasi-electrostatic field is used to promote the perception of the existence of the object. In addition to aiming at practicality of perception of signs using quasi-electrostatic field with the subject wearing HMD, we exhibited at Entertainment Computing 2019 [5] to find further possibilities of this research.

2 Purpose

In this study, the team proposed a method of perceiving a sign in an HMD using a quasi-electrostatic field as a perception of a sign that does not depend on vision andhearing. As described in Sect. 1, most of HMD-based games simulate only the visual and audio, leaving users only able to experience 2 senses. Using a quasi-electrostatic field, which is one of the factors causing this sensation, the team proposed a new way of perceiving a sign to further enhance the immersion of the HMD game and increase the range of experience. For example, considering the operation in a horror game, when a ghost is slowly approaching, a quasi-static electric field can be used to encourage the perception of the invisible ghost. Also, the usefulness of presenting a sign by using a quasi-electrostatic field emitted from a CRT television was evaluated by comments from users.

3 Related Work

An immersive auditory display Sound Cask [6] developed by Ito is one of the systems that promote the perception of signs. In this Sound Cask, it is possible to know the space while moving the head under the same conditions as in real space by generating a 3D wavefront around the head. The generated 3D wavefront allows you to hear sounds that are almost the same as in real space, that is, breathing and walking sounds of people around you. As a previous study using quasi-electrostatic field, according to Odagiri et al. (1989), in humans, the electrostatic field is perceived by minute vibrations of body hair caused by the electrostatic field [7]. Chen et al. (2014) investigated changes in pedestrian behavior due to quasi-electrostatic field [8]. In this research, we are experimenting with quasi-electrostatic field emitted from CRT(cathode-ray tube) television. The average distance to feel the quasi-electrostatic field when using a CRT television was 43 mm, indicating that the distance felt by women was about 10 mm longer than the distance felt by men. Suzunaga et al. (2019) proposed the presentation of fear using quasi-electrostatic fields and cold air [9]. In this research, a handset-type device is charged to stimulate the vicinity of the inner ear, which is one of the organs that are susceptible to a quasi-electrostatic field when placed on the ear, to give a thrill.

4 Method

4.1 Selection of Direction

In this experiment, the body hair is directly stimulated by a quasi-electrostatic field and the object’s sign is presented to the subject. Therefore, the presentation should be directed toward the feet where the skin is relatively easy to expose. In this paper, we adopted a method of stimulating using a CRT television used by Chen et al. (2014) as a transmitter that emits a quasi-electrostatic field [8]. Also, since it is necessary to distinguish between the quasi-electrostatic field emitted from the human body and the quasi-electrostatic field emitted from the transmitter, we created a mechanism as shown in Fig. 1 The servo motor can be used to turn on/off the transmitter so that the experiment can be performed without approaching the subject. In order to cut off the high-frequency sound generated from the transmitter, both subjects in experiments 1 and 2 were wearing headphones.

Fig. 1.
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System configuration

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4.1.1 Purpose

In experiment 1, the quasi-electrostatic field generated from a CRT television is stimulated from the front, back, left, and right of the foot to determine whether there is a difference in how the foot felt different stimulations and from where is the stimulation most pronounced. At the same time, we confirmed how much the quasi-electrostatic field can actually be felt.

4.1.2 Experiment

The system shown in Fig. 2 and 3 was constructed. A transmitter was installed at a position 40 mm away from the test subject, and the operation of turning off the power in 3 s after turning on the transmitter in the front, back, left, and right, and turning on the power 3 s after turning off the power were repeated four times. As a measurement method, when the subject indicates feeling any change, the team would ask the subject to describe the state at that time in detail. Counting was performed when subjects mentioned specific phrases such as “tingling”, “fluffy”, and “felt something”. In Table 1, we calculated the average of how many times subject could feel it during the 4th session, and the total average of the subjects and the sexes of the subjects and subjects.

Table 1. Ease of feeling of quasi-electrostatic field in front, back, left and right.
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Fig. 2.
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State of experiment 1.

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Fig. 3.
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Experiment 1 experience schematic diagram.

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4.1.3 Results and Discussion

The experiment shows that the effect of the quasi-electrostatic field can be felt more often when the power is turned on the left and right of the foot. Some people could not feel it at all. This is due to the fact that when humans feel a quasi-electrostatic field as described in Sect. 2: Related Work, they are perceived by minute vibrations of the body hair, and it is thought that they cannot be felt when there is no body hair.

4.2 Generation of Quasi-electrostatic Field

4.2.1 Purpose

In experiment 2, the research team investigated whether a quasi-electrostatic field was generated when approaching an object in the 3D space displayed on the HMD, and the direction of the object could be perceived and directed. In Sect. 4.1.2, it was found that there were people who could not feel the influence of the quasi-electrostatic field. For that reason, in this experiment, the experiment was conducted on two men and women who were able to feel the effect of the electrostatic field in Sect. 4.1.2.

4.2.2 Experiment

The system shown in Fig. 4 was constructed. The research team prepared a 3D space with low traffic dim streets and a T-shaped road with objects hidden in the alley. The subjects walked down the alley using the controller and turned on the device when approaching the T-shaped road. During the experiment. the experimenter would explained that, “from now on, I’ll have you walk in the alley. You might feel people’s eyes and signs from somewhere. If you feel them, please look over there.” Also, as in Sect. 4.1.2, the team asked the subjects to utter details of the situation at the time of occurrence. Figure 1 proved that stimulation of the left and right feet was effective, so the research team conducted experiments when placing the object on the left and on the right. When two males and two females were stimulated from the left and right of their feet, they performed the action such as they are directed to the direction of the object (the direction of stimulation), look around, and look into the T-shaped.

Fig. 4.
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Experiment 2 experience schematic diagram.

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4.2.3 Results and Discussion

Since the stimulation to the left and right of the foot was found to be effective in Sect. 4.1.2, it was confirmed that the effect of the quasi-electrostatic field could be presented in this experiment as well, and that it could actually be presented. Also, the result of looking around and looking into the T-shaped despite stimulating the foot was obtained. I think this is what Gary R. VandenBos showed, due to visual superiority [10], which is “the tendency to become aware of visual stimuli even when auditory and other stimuli are presented simultaneously”.

5 Application

5.1 System Configuration

5.1.1 Hardware Configuration

As a hardware configuration, the method of changing the power supply state using Solid State Relay was changed instead of the method (Fig. 5) of changing the power supply state by the servo motor implemented in Sect. 4.1. The reason for changing the configuration is that the method using the servo motor has problems such as the installation of the servo motor becoming unstable after being executed many times and the malfunction of the servo motor due to static electricity generated from the CRT television. Therefore, by using Solid State Relay to manage the power ON/OFF, the above problem was solved, and the software can be controlled stably from the software side.

Fig. 5.
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Improved control device.

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Fig. 6.
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Application configuration diagram.

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5.1.2 Software Configuration

The application software was created using Unity, a game engine. Creation of stages and quasi-electrostatic field presentation gimmick were done with reference to Sect. 4.2.2. The team also prepared a long corridor model in Scene. The subject advances the corridor with one button on the controller. The hallway was made dark to prevent light from entering. The end result is a stage that looks like a night school corridor that can be navigated using a flashlight controlled by the controller. An invisible ghost is placed on the way of the corridor and appears when subjects illuminate the place with the flashlight. Some people have a hard to feel the quasi-electrostatic field, and as a countermeasure for when the position of the ghost is not known at all, a button that displays a mark using particles is prepared. By doing so, the team designed as much as possible to find ghosts. Also, when the subject approaches the ghost, the system detects the location of subjects and ghosts and turns on the television. This operation is repeated about five times at intervals and the state of the subjects is observed. Within the experience, when the subject arrived at the end of the corridor, it automatically enters the door and loads the scene and ends the experience.

5.1.3 Application Configuration/Overview

Subjects wear HMD and sit on a chair with controller. Subjects start the experience with a CRT television installed on both sides of the feet. As an application story, subjects were instructed to go to the school classroom to collect forgotten items. There are many ghosts lurking in the school at night, so subjects get to safely collect forgotten items by searching for the ghost signs with their flashlight. Here, as described in Sect. 5.1.2, by presenting a quasi-electrostatic field where ghosts are to be present, it provides an experience where subjects can feel the ghosts that are invisible to the eye (Fig. 6).

6 Entertainment Computing 2019 Exhibition

To summarize the results and discussion of previous research, the research team actually exhibited what was created in Sect. 5.1.3 at Entertainment Computing 2019 to seek further opinions. Entertainment Computing 2019 is held every year as an academic conference since 2003. New technology for Entertainment Computing, new possibilities of Entertainment Computing, and relationship between Entertainment Computing and people and society, was a theme this year. Why the team chose Entertainment Computing 2019 was due to considering the operation of the game using HMD as the goal of this research. For that reason, because by presenting the research results at the famous Entertainment Computing Society in Japan, it was thought that the team could obtain valuable opinion from third parties about the possibility of further research and the problems of this research.

6.1 Experimental Result

6.1.1 Consideration

Positive feedback obtained throughout the exhibition include: “I could feel the quasi-electrostatic solution generated from the left and right a CRT television and perceive the direction in that direction” and “After feeling that sign, I was able to find a ghost quickly”.

6.1.2 Bad Point

On the other hand, negative opinions such as “Despite feeling sign to the feet, ghosts appeared not from where the sign originated from”, “Isn’t it possible to have such a strong static electricity against an ambiguous thing?”, “The ghost that comes out is too cute and scary”, and “I didn’t feel a quasi-electrostatic completely” were given.

6.2 Consideration

6.2.1 Good Point

While experiencing in state with only the HMD and controller attached, the subjects were able to feel the sign from a CRT television and notice the direction. From this result, the team felt that the presentation of the sign by a CRT television was useful.

6.2.2 Bad Point

The team thought that: “as a result of dragging the experiment in Sect. 4.2.2, there was a sense of incongruity due to the disagreement between the position of a CRT television and the appearance of ghosts in software”, “The strength of the quasi-electrostatic field when the television is turned on and off is too great as a cause of tactile presentation that jumps over the image that it may be ghosted”, “Some people thought of a scary ghost that just listen to the keywords ghost and sign”, “After all, the presence or absence of body hair to resonated greatly with whether or not we felt quasi-electrostatic field, and there was a lack of countermeasures” against bad opinions.

6.3 Improvements

As an improvement point, I thought that it would be necessary to review the presentation method of the quasi-electrostatic field and create content that matches it. In particular, instead of using a CRT television as a presentation method, the team thought that it would be necessary to create a small device that can easily present a quasi-electrostatic field other than a foot. In content, I thought that the position when presenting a quasi-electrostatic field to the subjects and the position felt in the content should be matched to make it easier to understand the position where you feel the sign.

Fig. 7.
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Future work

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7 Conclusions and Future Work

In this paper, the place the presentation of the quasi-electrostatic field which uses aCRT television in the main research and made the experience for the purpose of perception of signs, such as feel something also to the part that made the presentation of quasi-electronic field in a state of wearing the HMD. Inside, subjects were able to feel the quasi-electrostatic field and said “I left an impression that I feltsomething like “spring” and “fluffing” as revealed in Sect. 4.1.2. Based on these results, itwas shown that it is useful to the quasi-electrostatic field on a CRT television to promote the perception of signs to subjects wearing HMD as described in Sects. 4.1.1 and 6.1.1. However, as discussed in Sect. 4.1.3, people with little body hair did not feel the quasi-electronic field at all and this appears to be the problem of this device. It is difficult to feel when there is no body hair on the legs because the quasi-electrostatic field was presented toward the foot without contact. Furthermore, the parameter of the quasi-electrostatic field changes depending on how the object walks as originally mentioned in Sect. 2. To solve the problem from these experimental results, it was concluded that there would be a need for a device that could vary the capacitance and present it. From these findings, the first is a device that can be compact and fit so that many people can feel it. For that reason, the research team believed that it is necessary to provide a presentation method that a position closer to the downy hair to adhere with human skin, research on quasi-electrostatic field generation methods and presentation methods other than a CRT television, to create a device that allows one to perceive a sign with or without hair. Also, the team believed it is necessary to make a device that can present a quasi-electrostatic field other than the neck, such as presentation on the neck and back.

Furthermore, it was found in Sect. 6.1 that there are many software problems. In order to present an immersive feeling, one of the important factors in creating VR contents, the five senses that account for more than 80% of the perception of information is important. Accordingly, as mentioned in Sect. 6.2.2, it is necessary to modify the design so as not to give a sense of incongruity of the difference due to the position shift of the perceived position of the sign in the real world and the perceived position of the sign in the software. Also, by improving the visual to match the content, it was thought that it can be improved to be more convincing. Based on these findings, thefinal concept is a visual and immersive experience that matches the content. It was thought that it was important to finish things that are not to a sense of incongruity by having many people experience it (Fig. 7).