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CHUNG-MIN YU AND CHUNG-MING WANG
Department of Computer Science and Engineering
National Chung Hsing University
Taichung, 402 Taiwan
In many multimedia applications such as computer games, flight simulation, and special
effects for movies, clouds play an important role. In this paper, we present a variety of
techniques for cloud modeling, cloud rendering, and cloud morphing in order to make the
visual appearance of clouds in these applications more effective and interesting. For cloud
modeling, we propose a polygon sampling technique that enables users to accurately model
various types of cloud shapes from a 2D image. Moreover, if a 3D model is available, we
provide a tetrahedron sampling method to model the cloud. In cloud rendering, we present
two line integral convolution (LIC) techniques. The first technique eliminates the Gaussian
blobs caused by the splatting algorithm that is commonly used in conventional cloud rendering
while the second one produces a sky plane which increases the visual appearance of
the cloud rendering. Finally, we present a ¡§greedy¡¨ morphing algorithm for the purpose of
cloud morphing. This algorithm allows a gradual transition of smooth cloud shapes during
the animation process with only a limited number of frames. Our techniques increase the
visual realism of the appearance of clouds.
Received October 19, 2009; revised March 13 & May 11, 2010; accepted June 10, 2010.
Communicated by Tong-Yee Lee.
* This paper was partially supported by the National Science Council of Taiwan, R.O.C. under Grant No. NSC
98-2221-E-005-073-MY3.