Water Dome -An Augmented EnvironmentYuki Sugihara and Susumu Tachi
Dept. of Mathematical Engineering and Information Physics,
The University of Tokyoyuki @star:t.u-tokyo.ac.jp, tachi@star:t.u-tokyo.ac.jp
Abstract

Recent investigations have demonstrated that a threedimensional screen can play an important role in a virtualenvironment. It has been proposed that a wide-angle
display such as Omnimax, a spherical screen, might beused to create a virtual immersion experience for its
viewers[ I]. It is clear that these cubic displays are suitable
for the creation of three-dimensional space[2] [3]. Whilefountain technology has been developing for water screen
applications over the past 15 years, projected images havebeen used in conjunction with mist and streaming water atsome theme parks. Figure 1 shows examples of screen
sizes. The sense of being surrounded and immersed
depends on how much the screen is enlarged. Recent
trends in screen shapes are three-dimensional. Large
screens emphasize the feeling of being entertained. Domeshaped displays have been developed primarily to enhancethe visual field by surrounding a participant with a curved
surface. However, this system offers more than the senseof sight alone. For instance, the screen walls eliminate
outside sound and amplify inside sound. Therefore, we
proposed that water serve as a display material. The use of
a water dome enables participants to really experience thespace.
Visitors may see the real world as it is projected through athin wall of water with the sound of the rain. The water
dome is proposed as a method to challenge all five senses
in a virtual reality experience.

The purpose of this research is to demonstrate theinfluence that a water dome has on a person. The
following approach was used for this study:( I ) A water display was used as a projection screen;( 2 ) The illusion of being under water was created; and(3) Experiments with water domes of various sizes werecarried out.
Water display is a head mounted type water membrane.
When the display is projected, the inside surface acts as aconcave mirror that can reflect the hand and face of aparticipant. Water dome is a hemisphere eight meters indiameter. Participants were allowed to see the real world
through a transparent wall of water on which computergenerated images were projected. A water dome has theadvantage of engaging a participant's five senses as itenhances the surrounding environment. We developed awater dome that incorporates the points of view of boththe artist and the engineer.

1. Introduction
1.1 Background.
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2. System Design%

2.1 The size of the water display
Falling water creates a water display when it strikes anobject. In particular, a laminar flow creates a smooth andthin water membrane. A turbulent flow such as watergushing from a pipe does not create a membrane. Figure 2
lists the technical elements of a water display. We first
verified the six prerequisites for a water display. The
construction of a water dome has its roots in fluid
dynamics. We observed a combination of a flat and areality
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The water dome creates a transparent film of water
upon which lights may be projected[5]. Figure 4 shows thereflection on the water display. When a projector is set up
in the rear of the display, onlytibarticipants who stand in
front of the display may observe the lights. Projected
images are invisible to the visitor who is located next tothe projector. The light reflection depends on the angle ofincidence to the surface of the water. As the angle ofincidence increases, the percentage of the light reflection
on the surface of the water increases as well. Therefore,
the top arc of the water display reflects half of the light sothat it shines the brightest. The center of the display
becomes the screen, which shows penetrated and diffusedlight that makes up the projected images. A participant
who faces the projector through the water display may see
the images clearly. Consequently, it is advantageous to set
up the projector at an oblique angle in order to avoid
having any participant directly face a light source.

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Figure 2. Elements of water membrane"r---/

Figure 4. Reflection on the water display

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3. Presentation
3.1 Water display

circular surface, and we concluded that a gentle stream isthe best for constructing a hemisphere with a water
membrane[4]. We next collected data and examined therelationship between the quantity of the water to be used
and the diameter of the water exhibit.
Figure 3 demonstrates that as the flow rate of a pumpincreases, the diameter of the water dome increases aswell. We experimented with water displays ranging in
diameter from ten centimeters to eight meters. A water
membrane loses its smoothness when the diameter of thefountain exceeds two meters. At that point, its formchanges into streaming water. Regardless of how the waterflow is changed, the water display retains a hemispherethat can be entered. In addition, a curtain of water formedby multiple water jets forms a background suitable forimage projection.

The water dome is empty inside. We examined theinner water display for the sense of sight, hearing, touch,and feelings that it would convey. Figure 4 shows a headmounted water display that we developed in 1998[6]. The
water circulates through the pipes with a 50-liter perminute pump. The water display is formed on a doughnutshaped pool that is 70 centimeters in diameter. A
participant may duck under the edge of the pool and standbeneath the water. The viewer's head remains dry because
the inside of the dome is empty; however, the water
display sometimes creates a refreshing light rain thatmoistens the face of the viewer. Visitors can enjoy seeing
and hearing the water from549

Figure 5. Head mounted water display

Figure 6. Projected image

inside the display. The sound from the dome isconcentrated inside the dome, and the falling water blocks
the sound from outside the dome. The water display
provides an unusual experience providing a viewer with awatery 360-degree view.
We would first like to explain how the water reflectsfrom the display. When the display is illuminated, theinside surface acts as a concave mirror that can reflect thehand and face of a participant. Figure 6 shows thereflection of a hand as it is raised to the surface. As a handcomes closer to the water membrane, its image becomeslarger, and as a hand is withdrawn, the image becomes
smaller.
We next examined the projection effect. Figure 7 (left)
shows projected letters of the alphabet that are scatteredon the water display. Only vague images can be seen on
the water. The display area requires medium ambient
light. Too bright an environment is not suitable for a water
dome. Considering the nature of the reflected images andthe need for low ambient light, we designed a new way toview the images on the water display. Figure 7 (right)
shows reflected images of a user’s hand emerging on thewater display. By moving the hand closer to the reflected
images, the images became clearer. The proximity of thehand to the water makes a reflection even in a brightly lit
environment. By moving one’s hand, one can search forinvisible information. The reflected images cannot be seenfrom the outside of the display

because the phenomena are virtual images.
A public demonstration of this display was given
during the SIGGRAPH[7] 1999 exhibit in Los Angeles,
CA, U.S.A. In a dark room, projected images may beobserved directly on the water display. A high beam
projects a sharper image on the water membrane. We
prepared a variety of images from a variety of sources. A
high-contrast source is easy to see on a water membrane.
For instance, white letters on a black background or
yellow stars on a blue background both project well. We
projected the word for “water” in many languages: Aqua
(Interlingua), dus Wusser (German), Vodu (Czech), andMizu (Japanese). The projected letters stand out crisply
against the background makmg an inviting and artistic
statement. The projections were changed every fiveseconds. Since the water display is created with circulatingwater, attention is first paid to the falling water. Because
the image on the water membrane is so weak and blurred
due to the speed of the falling water, the image is notclearly recognizable. Participants approached the water
display, read the letters, and told us what feelings thewater display evoked. Figure 8 shows another sample of
the water display with projected images. A projected star
figure was most popular with the visitors. They were
reminded of a planetarium and experienced a fresh feeling.
When people stood under the water display, the moment
they noticed the images, they were actually moved. This
demonstration brought

Figure 7. Reflected image

Figure 8. Projected image

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Figure 9. Water dome project in Spiral, 1999

effect. If the animation moves across the dome, it seems
like more depth is acquired. The flowing water created aliquid dome vivid with color and sparkling on the water. In
addition, the water dome permits double images to bereflected because the dome has front and back layers.
Figure 10 shows the projected images on the dome.
Therefore, participants could be observed standing under
the projected water hemisphere. They appeared to becolored with floating blue waves, pink flowers, and whiterings. Participants inside the dome watched the images
that were being projected on the inner side of the dome
while they simultaneously experienced a fresh windblowing from the floor. The impressions that the
spectators reported are sensual. The feelings arise withwater ever present. They report sensations that often
accompany deep breathing, and the pleasures associatedwith dream-like sights. The display makes it possible tosuperimpose images on the surface of the dome. Actually,
the water dome is a see-through screen, The scene on theinside of the dome may be clearly seen from the outside ofthe dome. Participants on the inside of the dome mayforget that people on the outside of the dome may see

attention to the water display as a new medium, one thatcan serve as an information source because of the
projected images.

3.2 Water dome
Finally, we studied the effects of a large version of
the water dome. The first exhibit was a system forpersonal use. The head-mounted water display covers aviewer’s head. It does not support users in communication
with other people. Therefore, we created a water domethat many participants may enter simultaneously. A space
was created that was surrounded with images and water.
Figure 9 shows the water dome project on exhibit at the
Aoyama Spiral Garden. The water dome was exhibited inTokyo in November 1999. In order to accommodate 20
people, a stable stage with an eight-meter diameter and awater pipe with a four-meter height were used. A
temporary pool was built under the stage. Two 1000-liter
per-minute pumps spread the water out into the shape of adome. The jets of water gushed out of the top creating ascreen of water droplets. A screen of droplets produces abetter screen than the seamless membrane produced by atransparent, continuous flow of water. Although the water
form is changed, the light reflection and diffusion on thewater surface remains unchanged. For this reason, thesame images on the water surface could be seen from any
angle, and four projectors were placed around the water
dome. The content and the animation speed depend on thesize of the water display. Because a water dome has acurved surface, the projected images are distorted. Taking
that into account, geometric patterns of animation images
were projected in high-contrast. The distortion of theimages on the side of the water dome created a uniqueFigure 10. The projected image on the dome

them. The inside of the dome is much more stimulating

55 1

water dome under the stars. An outdoor use[8] of thewater dome is a logical next step. During the day, a water
dome serves as playground equipment that allows people
to experience what it would feel like to stand at thebackside of a waterfall. When evening comes, it will work
as a screen for graphic images.
It is especially important to emphasize the conceptthat water domes are transparent displays. The aspect oftransparency distinguishes the water dome from cubic
screens that may simultaneously be observed from insideand outside. Using water as a display material enables
projection from either side. Therefore, if we prepare two
projectors and project another image source on the water
display from an opposite side, we could see both images
on each surface because the light does not interfere andpenetrate the water display. At this point, a new water
dome system that consists of plural images with multiple
projectors is being investigated. It is possible to divide
water dome surfaces into screens for multiple projectors.
In the future, it is not inconceivable that every town might
have a fountain functioning as a medium for presenting
information. Moreover, it may be possible to project theactions of participants onto the water screens of the dome.

than the outside. The exhibit of the water dome in Tokyo
attracted 13,323 people. People of all ages andnationalities enjoyed the water dome. The project provided
people with sensations of fun, comfort, surprise, andrelaxation.

4. Augmented Reality
4.1 Use of a water screen
Since the baroque era in Europe, fountains have been
constructed in the center of cities. Italy has many
examples of such fountains that still serve as gathering
places. Such fountains still serve to light up the nights.
Fountains were popular gathering places because of theirrelaxing atmosphere. Water has a comforting power. In
addition, it can now be used as a medium for graphic arts.
There is a good example of a water screen currently
in use at Disneyland. It has a fan-shaped stream that iscreated by multiple jets of pulsing water. The fountain istransparent so that images may be projected on it. When I
saw the fountain at Disneyland, a real actor portraying
Mickey Mouse had a fight with a virtual witch projectedon the fountain. Mickey sometimes appeared in front of
the fountain and sometimes hid behind the fountain. This
was a good example of the entertainment potential of theuse of the water screen as an augmented reality. At thistime, not much thought had been given to the role thatspectators might play. Spectators currently watch the show
passively from a distance. Therefore, the following section
focuses on special features of the water dome.

5. Conclusion
This paper is a description of water domes that havebeen investigated and implemented. A water dome has theadvantage of engaging a participant’s five senses as itenhances the surrounding environment. In addition, thepossibility of image projection, interaction, andenlargement was also examined. Participants were allowed
to see the real world through a transparent wall of wateron which computer-generated images were projected. The
water dome proved to be popular with spectators. A
spherical screen provides a person with deep involvement.
Furthermore, it has the capacity to serve a small audience.
The potential of the water dome might be compared toinventions such as the Imax projection system andplanetariums. Fountains may take many forms; however,
we would like to continue to develop the water dome
because of its special characteristics. A dome was built in
London as a part of the recent millennium celebration. It isin that same spirit that we are creating our current water
domes. Literally, an artist often tries to change prevailingpoints of view. Our hope is that the water dome will makea contribution to the quality of life. Future water domes
could be used by the entertainment industry in amusement
parks or as exposition presentations, and they might evenfind uses in common towns as fountains for the projectionof information.

4.2 Water display and interaction
Water dome visitors may view a variety of images
while surrounded by water. Spectators can become
participants and play active roles in the water dome
experience. Participants’ opinions have ranged from“amazing,” “wonderful,” and “cool” to ‘‘I don’t know how
to describe it.” The water display presents multiple
elements regarding water, and participants feel fresh
sensations involving all five senses. It is reasonable tosuppose that the water dome is an interactive art on the
grounds that it prompts people to respond independently.
Interactive art and virtual reality share certain similarities
in that both deal with experiences of representation. The
water display demonstrates an augmented reality. The
water dome changes the environment for the viewer. Even
when the exhibition was held in a simple atrium of the
Aoyama Spiral Garden in Tokyo, participants felt as if theworld were altered. Some people wanted to experience the552

the Virtual Reality Society of Japan, 1999. [in Japanese]

6. References[l] Bolt,R.; “The Human Interface”, Lifetime Learning
Publications. 1984

[6] The First Intemational Symposium on Mixed Reality,“Media Art Gallery.” “Water display”, Yuki SUGIHARA,
Yokohama, Japan, March 9-11,1999[2] Cruz-Neira,C. et.al., “Surrounded-Screen Projection
Based Virtual Reality”, Proceedings of SIGGRAPH, U.S.A.,
1993.

[7] Yuki Sugihara and Susumu Tachi. “Water Display”,
Emerging Technologies at SIGGRAPH 99, Los Angeles, CA,
U.S.A., 1999. Conference Abstracts and Applications, pp. 183.

[3] Hiroo Iwata, “Rear-projection-based Full Solid Angle
Display” Proceedings of the Sixth Intemational Conference on
Artificial Reality and Tele-existence (ICAT ‘96), Tokyo, Japan,
pp.59-64[81 Ronald T. Azuma, “The Challenge of Making
Augmented Reality Work Outdoors”, Mixed Reality-Merging
Real and Virtual Worlds, 1999 Ohmsha, pp.379-399.

Acknowledgement
The Water Dome Project in Spiral is supported by the Japan Art
Scholarship Sixth Grand Prix Award.

[4] Yuki Sugihara, Keigo Yamamoto, and Hideki Hashimoto. “Aproposal for a Water Display” Proceedings of the Seventh
Intemational Conference on Artificial Reality and Tele-existence(ICAT ‘97), Tokyo, Japan, pp.63-70.

[5] Yuki Sugihara, Masahiko Inami, Naoki Kawakami, andSusumu Tachi, “Development of Water Display (2nd Report)- Image Projection Characteristics -”,The Virtual Reality Societyof Japan, Nara, Japan. Proceedings of the Fourth Conference of553