Kei Iwasaki Keichi Matsuzawa Tomoyuki Nishita The University of Tokyo
7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
Phone: +81.3.5841.4096 Fax: +81.3.5803.7288
{kei-i, keichi, nis}@nis-lab.is.s.u-tokyo.ac.jp
Abstract
In the field of computer graphics, simulation of physi- cal phenomena is of great interest. We focus on the optical effects of soap bubbles. Soap bubbles have fascinating col- oration and interesting physical properties. Therefore they are useful for the entertainment such as movies and games. Soap bubbles change their shapes by surface tension and external forces, and therefore their surface thickness also changes. Since the thickness of the soap bubble is several hundred nanometers, interference of the light occurs. This paper proposes a fast rendering method for the soap bub- bles taking into account light interference and dynamics. In our method, the reflectivities of the thin film that is the cause of the light interference are calculated in advance and stored as textures. This makes it possible to render the de- formable soap bubbles in real-time.
Keywords: light interference, graphics hardware, real-time animation
1. Introduction
The simulation of natural phenomena is one of the most challenging research fields in computer graphics. Soap bub- bles have interesting physical properties and attractive col- oration [15]. In this paper, we propose a real-time render- ing method for soap bubbles taking into account light in- terference. Soap bubbles form very thin layers. Since the thickness of the soap bubble is close to the wavelength of the visible light, fringes due to the light interference can be seen. Several methods have been developed to render the fringes [1, 2, 11, 12]. These methods employed a ray tracing algorithm to render the soap bubbles. Although re- alistic images can be generated by the ray tracing method, the computational cost is expensive. Thus, it is only suit- able for images and movies that do not require real-time response. However, applications such as virtual reality and games require real-time response. Therefore, the demand to accelerate the rate of rendering is high.
To address this problem, this paper presents a real-time rendering method for deformable soap bubbles taking into account light interference. In the proposed method, the re- flectivities of the thin film are calculated in advance and stored as textures. Moreover, the rendering of objects re- flected at the bubble surface is performed by using the dy- namic cubical environment map method.
2. Previous Work
Several methods have been proposed to simulate and ren- der the soap bubbles.
Dias [1] developed a method that modeled the interfer- ence light phenomenon and displayed the soap bubble with fringes. Li and Peng [11] extended Dias’ method to take the polarization of light into account. Icart et al. [9] simulated two dimensional soap froth. Glassner [4, 5] modeled the clusters of two or three soap bubbles by using analytical so- lutions for the geometry of soap bubble clusters. Dˇ urikoviˇc [3] treated a bubble as a set of particles and triangle patches. He simulated the deformation of soap bubbles due to wind forces and contacts with other objects. Ku ?ck et al. [10] sim- ulated and rendered the liquid forms by representing foam bubbles as fixed-size spheres. Realistic images of soap bub- bles can be generated by using these methods. However, these methods used a ray tracing algorithm whose compu- tational cost is expensive. There have been several related work about rendering light interference. Dias [2] proposed a rendering method of optical phenomena of Newton’s ring. Hirayama et al. [7, 8] developed a rendering method for the interference effect on multilayer films. They took into ac- count the smoothness of the surfaces coated with multilayer films and demonstrated several materials such as alminum, silicon, and copper. Sun [14] presented a method for trans- forming colors into spectrum and rendering light interfer- ence. These methods also employed a ray tracing algorithm for the rendering.
In this paper, we accelerate the rendering of soap bubbles taking into account light interference. The proposed method can calculate the light interference caused by the variation
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