Virtual Reality in Physical Mirrors

Seunghyun Woo∗ Takafumi Aoki∗ Hironori Mitake∗ Naoki Hashimoto∗ Makoto Sato∗Precision and Intelligence Laboratory, Tokyo Institute of Technology

ABSTRACT

Sometimes, mirrors provide illusions that distort physical laws. Inthese methods, the illusions become ”real” as your visual, tactile,and auditory senses are immersed in the world inside the mirror.Our methods allows you to experience a mirror illusion throughthree modalities of feedback (visual, haptic, and auditory) and per-ceive a boundary less transition between the real world and theworld inside the mirror. This approach is expected to open newpossibilities for using mirrors in the fields of media art or virtualreality.

Keywords: Interactive Interface with Physical Properties, Aug-mented Reality Perspective

Index Terms: H.5.2 [Information Interfaces and Presentation]:User Interface—Interaction styles; H.5.1 [Information Interfacesand Presentation]: Multimedia Information Systems—Artificial,augmented, and virtual realities

1 INTRODUCTION

We suggest methods which amplify a mirror illusion and expand itto the real world, surprising and amusing you through experiencethat mirror illusions realized outside of the mirror.

Some methods are being suggested which focus on mirror appli-cations in the fields of media art or virtual reality. Most only payattention to the relationship between the actual object and its reflec-tion. For example, they imitate the mirror [2] or a different imagefrom the actual object[1]. However, mirrors can also create illu-sions which seem to distort physical law: leaning of the horizon,twisting a solid object, cloning an object, and so on. Our meth-ods apply three modalities of feedback that make the alteration ofphysical law caused by the mirror illusion become real. These aremotions of a real object with respect to the horizon in the mirror,haptic feedback that seems to twist the object, and an increase ofa canon song’s complexity as the number of reflections increase.Through these methods, you can feel the world inside of the mir-ror, existing, connecting with, and affecting the real world. Yourbelief that the mirror realm is an illusion will change. Our methodswill surprise and amuse you through such feelings that you have notexperienced before.

2 MIRROR ILLUSION AND AMPLIFICATION METHOD

If you lean the mirror forward or backward, the horizon in the mir-ror also appears to lean. Similar to the real world which has gravity,the world inside the mirror also has gravity. For example, if gravityexists in the world inside the mirror in the same direction as the realworld, objects inside the mirror should slide down.Our first method focuses on objects inside the mirror, which seemto slide down when the mirror is leaned, allowing you to experienceanother world inside the mirror with gravity(Fig1). Through this,you can feel as if another world, like the real world, exists insidethe mirror.

∗e-mail: {stamwoo, aoki, mitake, naoki, msato}@hi.pi.titech.ac.jp

Figure 1: Variation in the horizon of the leaned mirror. (left:notleaned, right:leaned forward)

If you put an object underneath the mirror, the object in the realand the mirror realms seem like one linked object. At this time, ifyou lean the mirror forward or backward, the object underneath themirror appears to bend(Fig2). Our second method focuses on anillusion in which the object underneath the mirror seems to bend,and gives an opposing force allowing users to feel the bending ofthe object. Through this, you can feel as if the mirror realm isconnected with the real realm.

Figure 2: Variation of the object underneath the mirror when the mir-ror is leaned. (left:not leaned, right:leaned forward)

If you put an object underneath the mirror, the object in the realand the mirror realms seem like one linked object. At this time,if you lean the mirror forward or backward, the object underneaththe mirror appears to bend(Fig3). Our second work focuses on anillusion in which the object underneath the mirror seems to bend,and gives an opposing force allowing users to feel the bending ofthe object. Through this, you can feel as if the mirror realm isconnected with the real realm.

Figure 3: Variation of reflections when two mirrors fold V-form.(left:not folded, right:folded)

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3 IMPLEMENTATION OF THE REALITY IN PHYSICAL MIR-RORS

To prove the availability of our methods, we developed an applica-tion named ”Heaven’s Mirror”. ”Heaven’s Mirror” consists of threeparts : visual feedback, haptic feedback and auditory feedback.Our first work(visual feedback) focuses on objects inside the mir-ror, which seem to slide down when the mirror is leaned, puttingreal objects in motion with respect to the horizon in the mirror. Thisallows you to experience another world with gravity inside the mir-ror (Fig4, left). In this work, we measure the angle of the mirrorwith a rotary encoder and apply a conveyor belt and magnet systemto move the object (Fig4, right).

Figure 4: Left:variation of an object placed before the mirror whenthe mirror is leaned, Right:visual feedback system

Our second work(haptic feedback) focuses on an illusion inwhich the object underneath the mirror seems to bend, and givesan opposing force allowing users to feel the bending of the object(Fig5, left). In this work, we use a wire and DC motor with a ro-tary encoder for haptic feedback. Angle of the mirror is measuredwith the rotary encoder and opposing force is presented by the DCmotor. Haptic feedback varies with the width of the object, whichis measured by counting the number of photo-reflectors that go off(Fig5, right).

Figure 5: Left:variation of the object underneath the mirror when themirror is leaned. Right:haptic feedback system

Our third work(auditory feedback) focuses on variation of reflec-tions when two mirrors are folded V-form (Fig6, left). A music boxallows users to experience a canon song (Pachelbel’s Canon), whichincreases in complexity as the number of reflections goes up. Forexample, if you see two music boxes, two parts of the canon songwill be played. However if you see five music boxes, five parts ofthe canon song will be played. In this work, we measure the an-gle between the mirrors with a rotary encoder and use speakers topresent a canon song (Fig6, right).

Figure 6: Left:variation of the canon song complexity with the numberof reflections when two mirrors fold V-form. Right:auditory feedbacksystem

4 USER EXPERIENCE

”Heaven’s Mirror” has been presented several times in Japan andabroad. At these times, we collected interesting user reactions andreceived many comments through the exhibitions(Fig7).

Figure 7: View of exhibition (ACM SIGGRAPHASIA2008)

Most of the participants commented favorably on our works, es-pecially the concept of linking mirror illusions to real world effects.As one participant commented : ”Tangible interface that uses a mir-ror to play with physical objects in unexpected ways.” Some partic-ipants commented that this work can highlight a way of thinkingabout interfaces. They commented that these methods allow to re-alize the importance of considering the physical properties of thedevices as much as the digital leverage. Some participants com-mented that these methods have lots of potential applications. Someof them suggested about museum installations or pedagogical appli-cations.In case of visual feedback, many participants surprised at rolling theobjects. Even it is a simple principle but it is very effective to allowthe participants to immerse the work. In case of auditory feedback,many participants mistaked that they are using a real music box.They were confused by ”Turning the lever” and ”Playing the canonsong with speed of music box’s disk”.

5 CONCLUSION AND FUTURE WORK

We suggested three modalities of feedback that make the alterationof physical law caused by the mirror illusion become real. Threemodalities of feedback allows you to feel as if the boundary be-tween the real world and the world inside the mirror is continu-ous. To prove the availability of our methods, we developed anapplication named ”Heaven’s Mirror”. ”Heaven’s Mirror” has beenpresented several times in Japan and abroad. The participants com-mented favorably on our works.

It is very interesting fact that the mirror is recognized by tacileand auditory senses not only visual sense. Since the mirror is closedwith us from ancients time, interaction with the world inside themirror not only visual sense but also tacile and auditory sensesthrough VR technologies will be great amazement. We will con-sider the reason why they feel the illusions become ”real” and applyour methods. We also continue to hold exhibitions. We hope ourmethods will open new ways for the use of mirrors in virtual realityand stimulate future interactive creations.

REFERENCES

[1] Y. Kakehi and T. Naemura. Through the looking glass: you can playagainst your own reflection. In ACE ’05: Proceedings of the 2005 ACMSIGCHI International Conference on Advances in computer entertain-ment technology, pages 373–374, New York, NY, USA, 2005. ACM.

[2] D. Rozin. Wooden mirror. IEEE Spectr., 38(3):69, 2001.

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