[其它] Visual Simulation of Aurora Movement

彬彬

797 主题	1 听众	1万积分

资深设计师

Rank: 7 Rank: 7 Rank: 7

纳金币: 5568
精华: 0

电梯直达

楼主

发表于 2012-1-3 10:38:50 |只看该作者 |倒序浏览

1 Introduction

This paper proposes a new modeling method for visual simulation

of aurora.The proposed method generates an aurora animation

based on the simulation of the electromagnetic field and emission

principles. The proposed method has two major advantages (1) it

can mimic the phenomena including splitting and rotation, which

are observed in actual aurora, and (2) the color of aurora images

generated by the proposed method closely matches the actual aurora.

The proposed method can create realistic aurora animations.

Baranoski et al. have proposed a method for simulating and rendering

aurora based on the average approximation of the actuallyobserved

data [G. V. G. Baranoski 2003].This method was, however,

limited to static images, and there were some limitations

in the color of the aurora.Baranoski et al. later proposed

another method for modeling aurora-dynamics simulation

[G. V. G. Baranoski 2005].This method can reproduce a rotation

of aurora on thin sheets by simulating forces of electrically

charged particles.This method, however, could not reproduce

a splitting.Ishikawa proposed a method for predicting the region

over the earth where aurora is visible based on the observed

data [Tomokazu Ishikawa 2011].Although this method was effective

for predicting global movement of aurora, it could not generate

a detailed image of aurora.

2 Modeling The Aurora

The proposed method reproduces the aurora movement by simulating

the motions of charged particles.The rest of the paper denotes

y as altitude, and xz plane corresponds to the earth surface.The

proposed method defines the aurora curve, which is a linear combination

of B`ezier and sine curves defined on the xz plane.A width

is also defined at every point on the aurora curve.The aurora curve

with width information is given as input to the proposed method

and is used for calculating the initial positions of the charged particles.

The initial particles are randomly placed above the domain

defined by the aurora curve and the width, and y is 500km which

is the maximum altitude that aurora appears. The proposed method

creates a rectangular grid that encloses all the charged particles on

e-mail:kojima.takafumi0@gmail.com

ye-mail:s2rita@nifty.com

ze-mail:soji@andrew.cmu.edu

xe-mail:earth@media.teu.ac.jp

{e-mail:mikami@media.teu.ac.jp

xz plane and calculates Lorentz forces acting on the charged particles

at the grid points by simulating the electromagnetic field.The

particle positions are iteratively updated, and the grid size is also

updated after every iteration so that all the particles are always

within range of the grid.

The proposed method simulates charged particles falling through

Earth’s magnetic field. The proposed method determines the type

of the atmospheric particle that collided with a charged particle

based on the colliding position and the composition of upper atmosphere.

The method then calculates the wavelength of the light

radiated from the atmospheric particle based on the generation rate

of the excitation of each wavelength.If the atmospheric particle collides

with another atmospheric particle before emitting the light, it

loses energy and does not emit the light.

The proposed method renders the image of the aurora by projecting

the colliding positions to the screen and calculating the intensities

of emissions.The decrement of the light can be calculated from

the distance between the screen and the colliding position.Gaussian

filter is applied to the light intensities so that the aurora image is

smooth and continuous.

3 Conclusion

This paper has proposed a new modeling method for visual simulation

of aurora.Figure 1 shows snapshots of an animation generated

by the implementation.It successfully visualizes a band of

aurora fluttering.The method can reproduce the aurora movement

such as splitting and rotation and can render the aurora emission in

color. Future work of this research includes improving the modeling

method for simulating the magnetic variations and real-time

processing.These enhancements will make the proposed method

useful for wider variety of visual simulations.

References

G. V. G. BARANOSKI, JON ROKNE, P. S. T. T. R. B. 2003.

“simulating the aurora”. Visual. Comput. Animat, 43–59.

G. V. G. BARANOSKI, J. W. 2005. “simulating the dynamics of

auroral phenomena”. ACM Transactions on Graphics 24, 37–59.

TOMOKAZU ISHIKAWA, YONGHAO YUE, K. I. Y. D. T. N. 2011.

“modeling of aurora borealis using the observed data”. Proc. of

SCCG, 35–38.