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Journal of Information Science and Engineering, Vol. 27 No. 3, pp. 891-913 (May 2011)

An Effective Framework for Cloud Modeling, Rendering, and Morphing*

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.

Keywords: cloud modeling, cloud rendering, cloud morphing, line integral convolution, Gaussian blobs

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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.