The advantage and the disadvantage for 3-dimensional scientificvisualization with computer graphics
Tomohide Wada 111

Four-Dimensional Digital Universe Project, Center for Computatioal Astrohysics, National Astronomical
Observatory of Japan

Introduction

In scientific visualization for astronomical phenomena, wechoose 3-dimensional stereoscopic visualization with Computer
Graphics(hereafter, CG). Because CG has versatile
expressiveness, we can depict phenomena or physical law moreeducationally-valid and beautifully. Since 2005, FourDimensional Digital Universe project1 (hereafter, 4D2U) havebeen providing the instructive images which are originated bylatest numerical simulation for astrophysics. Especially,
stereoscopic viewing technique is helpful to understand theacademic significance and gives us immersive environment inuniverse. Recent years, in fashion 3D cinema made full use ofCG, scientific stereoscopic images attract rising attention.
2

The advantage of scientific stereovision

Our universe composed of 3-dimensional space and time. In
the universe, position and shape of object changes with time.
Ideally, stereoscopic view would express realistic 3-dimensional
space on the 2-dimensional screen or display. And therefore, we
can see phenomenon of nature which is regularly invisible suchas galaxy, Sun, neutron star and so on. (See Fig. 1.) Such images
will gives us aesthetic satisfaction. From now on, it is importantto produce the instructive images not only for entertainment ofpeople but also reliable information and intellectual stimulation.

visual recognition of human is sensitive about environment. In
other words, we can not always recognize the shape or color ofobject in 3-dimensional CG space. Here, we introduce someexamples of heteroptic in our works. It is noted that we could
not avoid heteroptic because heteroptic is mostly caused
physiologically.
3.1

Hollow face illusion
Fig. 2. shows time evolution of isosurface of entropy formagnetohydrodynamics simulation of supernova explosion3. For
visualization, it is important to draw the time evolution ofasymmetrical structure. View of camera directs the origin andrevolves around. To verify the asymmetric structure of insideisosurface, the half of isosurface is cutaway. From 2 to 6 in Fig.
2, some people experience the inversion of depth. This is called
hollow face illusion4. We confuse the depth and the structure ofisosurface.

Fig. 2. Cutaway view of isosurface
3.2

Misreading of Scale
CG can treat various size and shape of object. It would be
useful to distinguish the physical state. Fig. 3. shows misreadingof the scale. Although many people think (a) and (b) are
identical, (a) has two times larger radius than that of (b) but thedistance from camera is two times farther than that of (b). Somepeople would feel vertical length of (d) is larger than that of (b).
But the length of them is same. Slim structure causes
Fig. 1. Spiral Galaxy calculated by numerical simulation2.
Image credit 4D2U.
3Heteroptics by 3-dimensional drawing

CG can draw the object with quantitative parameters related
physical quantity or state. It is convenient to visualize the resultof numerical simulation. And therefore, the time evolution ofsystem could be expressed in 3-dimensional CG space, easily.
Although the stereoscopic view is useful to express the universe,
there is possibility to cause misreading in some situations. Theoverestimating of length.
Fig. 3. Example of misreading of scale

4Conclusion

We aim to produce reliable scientific images. And so, wefocus on the expression to explain phenomena from physicalstandpoint. Stereoscopic view with CG is one of the best method
to express the phenomena of nature. But we should not forgetsome situation leads misreading or heteroptics.
In Japan, Safety guidelines of 3D is proposed by 3D
CONSORTIUM5. Although the large depth of vision make us
eye fatigue in long time viewing of stereovision, discreet
rendering would make less enjoyable. If we enjoy short time
viewing in several minutes and eyestrain should be light, wecould try more impressive expression. It is difficult to define
the criteria of safety because the streoscopic effect andheteroptic is felt different degree each other. In the future work,
Improvement of images should be consider not just thegeometrical effect such as parallax but the psychological effect.
We will utilize the information gleaned from a questionnaire.
Acknowledgements
We would like to thank , Takeharu Seno, Hiroyuki Hagura andAkiyoshi Kitaoka for discussions and many helpful commentson the manuscript.
References
[1]
[2]
[3]
[4]
[5]

4-Dimensional Digital Universe project (4D2U), National
Astronomical Observatory, Japan. (http://4d2u.nao.ac.jp/)
Fujii, M., et al. Astrophysical Journal, volume 730, page 109 ,2011
Takiwaki , T., et al, Astrophysical Journal, Volume 749, page 98,
2007
Harold H.; Alan J,. Perception, volume 36, pages 199 -223, 2007
3D CONSORTIUM (http://www.3dc.gr.jp/jp/index.html)