Journal of the Korea Institute of Information and Communication Engineering (한국정보통신학회논문지)

The Korea Institute of Information and Commucation Engineering (한국정보통신학회)
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GPU-based modeling and rendering techniques of 3D clouds using procedural functions

절차적 함수를 이용한 GPU기반 실시간 3D구름 모델링 및 렌더링 기법

  • Sung, Mankyu (Department of Game & Mobile, Keimyung University)
  • Received : 2019.01.18
  • Accepted : 2019.02.21
  • Published : 2019.04.30
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Abstract

This paper proposes a GPU-based modeling and rendering of 3D clouds using procedural functions. The formation of clouds is based on modified noise function made with fbm(Fractional Brownian Motion). Those noise values turn into densities of droplets of liquid water, which is a critical parameter for forming the three different types of clouds. At the rendering stage, the algorithm applies the ray marching technique to decide the colors of cloud using density values obtained from the noise function. In this process, all lighting attenuation and scattering are calculated by physically based manner. Once we have the clouds, they are blended on the sky, which is also rendered physically. We also make the clouds moving in the sky by the wind force. All algorithms are implemented and tested on GPU using GLSL.

본 논문은 절차적함수를 이용하여 실시간으로 3차원 구름을 모델링하고 렌더링하는 알고리즘을 제안한다. 구름 모델링은 절차적 노이즈 함수인 fbm(Fractional Brownian Motion)을 변형하여 사용하며, 이 값을 대기의 수증기 밀도 값으로 이용한다. 이 밀도 값은 파라미터로 주어진 3가지 구름의 형태를 위해 변형되며 렌더링단계의 입력 값으로 들어간다. 레이마칭(ray marching)기법을 이용한 렌더링 단계에서는 이 밀도 값을 이용하여 구름의 색상을 결정하며 이때 밀도에 따른 빛의 감소 및 산란현상은 물리적으로 계산된다. 대기모델로 렌더링 된 하늘 위에 제안한 알고리즘에 의해 구현된 구름들이 블랜딩되며, 이 때 바람의 방향에 따라 구름이 움직이도록 한다. 제안된 구름 생성 및 렌더링은 GLSL언어를 이용해서 GPU상에서 구현되었다.

Keywords

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Fig. 1 Three different cloud types [12]

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Fig. 2 Ray marching algorithm overview

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Fig. 3 Cloud Rendering Process

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Fig. 4 Atmosphere rendering (OceanColor=(0, 0.73,0.95) ColorNearHorizon=0.0, 0.16, 0.51)

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Fig. 5 Cloud Rendering: (a) cumulus (b) stratocumulus(c) stratus (f = 2.57 r = 0.5 #of octave = 5 g=0.99 b=.19)

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Fig. 6 Cloud coverages : (a) 0.2 (b) 0.5 (c) 0.75

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Fig. 7 Visual comparison of rendering result with [10] (Top : result of [10], Botton : Proposed algorithm)

Table. 1 Performance

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References

  1. E. Cerezo, F. Perez, X. Pueyo, F. J. Seron, and F. X. Sillion, "A survey on participating media rendering techniques," Visual computer, vol. 21, no. 5, pp. 303-328, Jun. 2005. https://doi.org/10.1007/s00371-005-0287-1
  2. R. Hufnagel, and M. Held, "A survey of Cloud Lighting and Rendering Technique," Journal of WSCG, vol. 20, no. 3, Jan. 2012.
  3. F. Haggstrom, "Real-time rendering of volumetric clouds," M. S. dissertation, Umea University, 2018.
  4. A.Schneider, "The Real-time Volumetric Cloudscapes of Horizon: Zero Dawn," SIGGRAPH Course note in Advance in Real-Time Rendering in Games, 2015.
  5. T. Akernin-Moller, E. Haines, and N. Hoffman, Real-Time Rendering, 4th Edition, CRC Press, 2018.
  6. C. Crassin, F. Neyret, S. Lefebvre, and E. Eisemann. "GigaVoxels: Ray-guided streaming for efficient and detailed voxel rendering," in Proc. ACM SIGGRAPH Symp.on Interactive 3D Graph. and Games (I3D), 2009.
  7. T. Nishita, Y. Dobashi, and E. Nakamae, "Display ofclouds taking into account multiple anisotropic scattering and skylight," in Proc. ACM SIGGRPH, pp. 379-386, 1996.
  8. I. Quilez, Terrain Raymarching [Internet]. Available: http://www.iquilezles.org/www/articles/terrainmarching/terrainmarching.htm, 2002
  9. E. Vane, "Cloud Rendering using 3D Textures," University of Waterloo, Technical Report, 2004.
  10. L. J. Tomczak, "GPU Ray marching of Distance Field," M. S. dissertation, Technical University of Denmark, 2012.
  11. W. Engel, GPU Pro 7:Advanced Rendering Technique, CRC Press, 2016.
  12. A. J. Preeham, P. Shieley and B. Smits, "A Practical analytic model of daylight," in Proc. ACM SIGGRPH, pp. 91-100, 1999.
  13. I. Quilez, 2D distance functions [Internet]. Available: https://iquilezles.org/www/articles/distfunctions2d/distfunctions2d.htm, 2018
  14. G. Bodare, and E. Sandberg, "Efficient and Dynamic Atmospheric Scattering," M. S. dissertation, Chalmers University of Technology, 2016.
  15. E. Yosov, "High-Performance Rendering of Realistic Cumulus Clouds Using Pre-computed Lighting," in Proceeding of High Performance Graphics, 2014.
  16. G. Seller, R. S. Wright, Jr, and N. Haemel, OpenGL Super Bible : Comprehensive Tutorial and Reference, 7th Edition, Addison-Wesley Professional, 2015.