基于物理过程的水流仿真
|
摘要
近年来，在许多虚拟现实系统中需要动态仿真水流运动，为了增加系统的真实感，就要正确地对水流进行仿真，其关键是建立恰当的模型和采用适当的渲染算法。许多现有的流体模型只能单独描述流体的某些属性，不能同时描述流体的一些重要属性，如：速度，高度域等，而这些属性在很多与水流有关的仿真系统中是必不可少的；传统的光线跟踪渲染算法能够产生具有很强真实感的图形，但是不能够满足实时的需求。
本文针对上述背景，总结了现有的各种水流建模方法以及渲染算法的研究现状。在此基础上给出基于压力高度域的水流模型，并阐述了该模型的合理性。同时分析了Fresnel函数的特点，给出基于纹理映射和分段近似Fresnel函数的水流渲染算法。为了生成满足水流模型空间大小的纹理，本文给出了搜索带加速的WL纹理合成算法。最后在VC++和OpenGL环境中实现了一个简单的实时动态水流仿真系统。
本文讨论的模型能够描述水流的多种属性，这增加了模型的应用范围；同时渲染算法能够满足实时需求。进一步的工作是如何将渲染算法和硬件特性结合以进一步提高仿真系统的速度；同时在纹理中反映光照对水流表面的影响。
Currently, in many Virtual Reality Systems, there is an increasing need for simulating the fluid behaviors dynamically. To obtain more realistic scene, simulating physically realistic fluid behaviors is very important. Many fluid models just present only one aspect of fluid, and can' t present some important properties simultaneously, such as speed, heightfield etc. .which are necessary in many fluid simulation systems. Although the traditional raytraced-based rendering algorithms can obtain high quality graphics, they can' t be used in Real-Time Systems.
This paper investigates the existing fluid models and rendering algorithms firstly. Then, a pressure-based height field fluid model is proposed and the pressure to simulate the fluid surface height is justified. The rendering algorithms based on the use of texture maps and piecewise approximate Fresnel formula of reflection is proposed after analyzing the Fresnel formula. To get texture maps at appropriate size, an accelerated method for Wei and Levoy' s basic algorithm (for short, WL algorithm) is presented. Finallly, a real-time fluid simulation system is implemented with VC++ and OpenGL.
The pressure-based height field fluid model can present many important properties of fluid and thus can be used widely. A Real-Time System can be achieved with the model and rendering algorithms proposed in this paper. Further research is how to improve the speed of simulation system by considering the properties of graphic hardware and presenting the illumination in texture maps.
本文针对上述背景，总结了现有的各种水流建模方法以及渲染算法的研究现状。在此基础上给出基于压力高度域的水流模型，并阐述了该模型的合理性。同时分析了Fresnel函数的特点，给出基于纹理映射和分段近似Fresnel函数的水流渲染算法。为了生成满足水流模型空间大小的纹理，本文给出了搜索带加速的WL纹理合成算法。最后在VC++和OpenGL环境中实现了一个简单的实时动态水流仿真系统。
本文讨论的模型能够描述水流的多种属性，这增加了模型的应用范围；同时渲染算法能够满足实时需求。进一步的工作是如何将渲染算法和硬件特性结合以进一步提高仿真系统的速度；同时在纹理中反映光照对水流表面的影响。
Currently, in many Virtual Reality Systems, there is an increasing need for simulating the fluid behaviors dynamically. To obtain more realistic scene, simulating physically realistic fluid behaviors is very important. Many fluid models just present only one aspect of fluid, and can' t present some important properties simultaneously, such as speed, heightfield etc. .which are necessary in many fluid simulation systems. Although the traditional raytraced-based rendering algorithms can obtain high quality graphics, they can' t be used in Real-Time Systems.
This paper investigates the existing fluid models and rendering algorithms firstly. Then, a pressure-based height field fluid model is proposed and the pressure to simulate the fluid surface height is justified. The rendering algorithms based on the use of texture maps and piecewise approximate Fresnel formula of reflection is proposed after analyzing the Fresnel formula. To get texture maps at appropriate size, an accelerated method for Wei and Levoy' s basic algorithm (for short, WL algorithm) is presented. Finallly, a real-time fluid simulation system is implemented with VC++ and OpenGL.
The pressure-based height field fluid model can present many important properties of fluid and thus can be used widely. A Real-Time System can be achieved with the model and rendering algorithms proposed in this paper. Further research is how to improve the speed of simulation system by considering the properties of graphic hardware and presenting the illumination in texture maps.
引文
[1] 彭群生，鲍虎军，金小刚，计算机真实感图形的算法基础，科学出版社，1996．6．
[2] D. Ebert, K. Musgrave, P. Prusinkiewics, J. Stam, and J. Tessendorf. Simulating nature: From theory to practice. ACM Siggraph ' 00 Course Note, September 2000.
[3] G. Miller and A. Pearce, Globular Dynamics: A Connected Particle System for Animating Viscous Fluids, Computers and Graphics, Vol. 13, No. 3, 1989, pp. 305-309.
[4] Michael E. Goss, A Real Time Particle System for Display of Ship Wakes. IEEE Computer Graphics and Applications, Vol. 10, No. 3, May 1990. pp. 30-35.
[5] Fournier A., Reeves w. T, A simple model of ocean waves Computer Graphics, Vol. 20, No. 4,1986, pp. 75-84.
[6] Peachey D.R , Modelling waves and surf , Computer Graphics, Vol. 20, No 1. 4,1986, pp. 64-74.
[7] P.Y. T' so and B. A. Barsky, Modeling and Rendering Waves:Wave-Tracing Using Beta-Splines and Reflective and Refractive Texture Mapping, ACM Trans. on Graphics, Vol. 6, No. 3, July 1987, pp. 191-214.
[8] 鄢来斌，李思昆，张秀山，虚拟海战场景中的海浪实时建模与绘制技术研究，计算机研究与发展，Vol．38 No．5，May 2001，pp．568-573．
[9] 杨怀平，胡事民，孙家广，一种实现水波动画的新算法，计算机学报，Vol．25，NO．6，2002，pp．612-617．
[10] Chen J X, Lobol N D V, Toward interactive-rate simulation of fluids with moving obstacles using Navier-Stokes equations, Graphics Models and Image Processing, Vol. 57, No. 2,1995, pp. 107-116.
[11] Jim X. Chen, Niels da Vitoria Lobo, Charles E. Hughes, and J. Michael Moshell, Real-Time Fluid Simulation in a Dynamic Virtual Environment, Computer Graphics, Vol. 17, No. 3, May-June 1997, pp. 52-61.
[12] M. Kass and G. Miller, Rapid, Stable Fluid Dynamics for Computer Graphics, Computer Graphics, Vol. 24, No. 4, Aug. 1990, pp. 49-55.
[13] Anita T. Layton and Michiel van de Panne, A Numerically Efficient and Stable Algorithm for Animating Water Waves, The Visual Computer, Vol. 18, Issue 1, 2002, pp. 41-53.
[14] 徐迎庆，苏成，李华，刘慎权，齐东旭，基于物理模型的流水及波浪模拟，计算机学报，Vol．19，增刊，1996，pp．150-163．
[15] Richard S．Wright，Jr．Michael Sweet，潇湘工作室 译，OpenGL超级宝典，人民邮电出版社2001．6．
[16] 刘全，水鸿寿，张晓轶，数值模拟界面流方法进展，力学进展，Vol．32，No．2，2002，pp．259-274．
[17] Jens Schneider, Rudiger Westermann, Towards Real-Time Visual Simulation of Water Surfaces, Proceedings of the Vision Modeling and Visualization 2001(VMV-01), pp. 211-218.
[18] Simon Premoze, Michael Ashikhmin, Rendering Natural Waters, Computer Graphics Forum, Vol. 20, No. 4, 2001, pp. 189-200.
[19] http://www. vterrain. org/Water/
[20] Simon P, Michael A, Rending natural waters, Proc of Pacific Graphics, 2002, pp. 23-30.
[21] 于金辉，徐晓刚，彭群生，用随机正弦波拟和卡通流水，计算机研究与发展，Vol．38，No．5，2001，pp．519-523．
[22] 陈前华，邓建松，陈发来，滴水涟漪的计算机动画模拟，计算机研究与发展， Vol．38，No．5，May 2001，pp．524-528．
[23] 王红卫，建模与仿真，科学出版社，2002，pp．17．
[24] 张涤明，蔡崇喜，章克本，詹杰民，黄海，计算流体力学，中山大学出版社，1991．5．
[25] 唐泽圣等，三维数据场渲染，清华大学出版社，1999．12．
[26] Catmull, E. and R. Rom, A Class of Local Interpolationg Splines," in Barnhill R.E. and R.F. Riesenfled (eds.), Computer Aided Geometric Design, Academic Press, New York, 1974.
[27] Hoppe H. View-Dependent refinement of progressive meshes, Computer Graphics (SIGGRAPH' 97 Proceedings). Los Angeles, CA, 1997, pp. 189-198.
[28] nVidia. nVidia Developer relations & Whitepapers. http://www. nvidia. com/Developer.
[29] Dru Clark, Michael Bailey, Visualization of height field data with physical models and texture photomapping, 8th IEEE Visualization '97 Conference, October 19 - 24, 1997, Phoenix, AZ.
[30] Li-Yi Wei, Marc Levoy. Fast texture synthesis using tree-structured vector quantization. Computer Graphics Proceedings, Annual Conference Series, 2000, pp. 479-488.
[31] Michael Ashikhmin. Synthesizing natural textures. ACM Symposium on Interactive 3D Graphics, 2001, pp. 217-226.
[32] 徐晓刚，于金辉，马利庄．多种子快速纹理合成．中国图形图像学报．Vol．7，No．10，2002，pp．995-999．
[33] Alexei A. Efros, William T. Freeman. Image Quilting for Texture Synthesis and Transfer. Computer Graphics Proceedings, Annual Conference Series, August 2001.
[34] Efros Alexei A, Leung Thomas K. Texture synthesis by non-parametric sampling. International Conference on Computer Vision, Greece:IEEE press, 1999:1033-1038 [30]
[35] 徐晓刚．纹理合成技术研究．浙江大学博士后研究工作报告．2001．11．
[36] Lin Liang, Ce Liu, Ying-Qing Xu, Baining Guo, and Heung-Yeung Shum. Real-Time Texture Synthesis By Patch-Based Sampling. ACM Transactions on Graphics. Vol. 20, No. 3, July 2001, pp. 127-150 .
[37] 和平鸽工作室，OpenGL高级编程与渲染系统开发，中国水利水电出版社，2003．1．
[2] D. Ebert, K. Musgrave, P. Prusinkiewics, J. Stam, and J. Tessendorf. Simulating nature: From theory to practice. ACM Siggraph ' 00 Course Note, September 2000.
[3] G. Miller and A. Pearce, Globular Dynamics: A Connected Particle System for Animating Viscous Fluids, Computers and Graphics, Vol. 13, No. 3, 1989, pp. 305-309.
[4] Michael E. Goss, A Real Time Particle System for Display of Ship Wakes. IEEE Computer Graphics and Applications, Vol. 10, No. 3, May 1990. pp. 30-35.
[5] Fournier A., Reeves w. T, A simple model of ocean waves Computer Graphics, Vol. 20, No. 4,1986, pp. 75-84.
[6] Peachey D.R , Modelling waves and surf , Computer Graphics, Vol. 20, No 1. 4,1986, pp. 64-74.
[7] P.Y. T' so and B. A. Barsky, Modeling and Rendering Waves:Wave-Tracing Using Beta-Splines and Reflective and Refractive Texture Mapping, ACM Trans. on Graphics, Vol. 6, No. 3, July 1987, pp. 191-214.
[8] 鄢来斌，李思昆，张秀山，虚拟海战场景中的海浪实时建模与绘制技术研究，计算机研究与发展，Vol．38 No．5，May 2001，pp．568-573．
[9] 杨怀平，胡事民，孙家广，一种实现水波动画的新算法，计算机学报，Vol．25，NO．6，2002，pp．612-617．
[10] Chen J X, Lobol N D V, Toward interactive-rate simulation of fluids with moving obstacles using Navier-Stokes equations, Graphics Models and Image Processing, Vol. 57, No. 2,1995, pp. 107-116.
[11] Jim X. Chen, Niels da Vitoria Lobo, Charles E. Hughes, and J. Michael Moshell, Real-Time Fluid Simulation in a Dynamic Virtual Environment, Computer Graphics, Vol. 17, No. 3, May-June 1997, pp. 52-61.
[12] M. Kass and G. Miller, Rapid, Stable Fluid Dynamics for Computer Graphics, Computer Graphics, Vol. 24, No. 4, Aug. 1990, pp. 49-55.
[13] Anita T. Layton and Michiel van de Panne, A Numerically Efficient and Stable Algorithm for Animating Water Waves, The Visual Computer, Vol. 18, Issue 1, 2002, pp. 41-53.
[14] 徐迎庆，苏成，李华，刘慎权，齐东旭，基于物理模型的流水及波浪模拟，计算机学报，Vol．19，增刊，1996，pp．150-163．
[15] Richard S．Wright，Jr．Michael Sweet，潇湘工作室 译，OpenGL超级宝典，人民邮电出版社2001．6．
[16] 刘全，水鸿寿，张晓轶，数值模拟界面流方法进展，力学进展，Vol．32，No．2，2002，pp．259-274．
[17] Jens Schneider, Rudiger Westermann, Towards Real-Time Visual Simulation of Water Surfaces, Proceedings of the Vision Modeling and Visualization 2001(VMV-01), pp. 211-218.
[18] Simon Premoze, Michael Ashikhmin, Rendering Natural Waters, Computer Graphics Forum, Vol. 20, No. 4, 2001, pp. 189-200.
[19] http://www. vterrain. org/Water/
[20] Simon P, Michael A, Rending natural waters, Proc of Pacific Graphics, 2002, pp. 23-30.
[21] 于金辉，徐晓刚，彭群生，用随机正弦波拟和卡通流水，计算机研究与发展，Vol．38，No．5，2001，pp．519-523．
[22] 陈前华，邓建松，陈发来，滴水涟漪的计算机动画模拟，计算机研究与发展， Vol．38，No．5，May 2001，pp．524-528．
[23] 王红卫，建模与仿真，科学出版社，2002，pp．17．
[24] 张涤明，蔡崇喜，章克本，詹杰民，黄海，计算流体力学，中山大学出版社，1991．5．
[25] 唐泽圣等，三维数据场渲染，清华大学出版社，1999．12．
[26] Catmull, E. and R. Rom, A Class of Local Interpolationg Splines," in Barnhill R.E. and R.F. Riesenfled (eds.), Computer Aided Geometric Design, Academic Press, New York, 1974.
[27] Hoppe H. View-Dependent refinement of progressive meshes, Computer Graphics (SIGGRAPH' 97 Proceedings). Los Angeles, CA, 1997, pp. 189-198.
[28] nVidia. nVidia Developer relations & Whitepapers. http://www. nvidia. com/Developer.
[29] Dru Clark, Michael Bailey, Visualization of height field data with physical models and texture photomapping, 8th IEEE Visualization '97 Conference, October 19 - 24, 1997, Phoenix, AZ.
[30] Li-Yi Wei, Marc Levoy. Fast texture synthesis using tree-structured vector quantization. Computer Graphics Proceedings, Annual Conference Series, 2000, pp. 479-488.
[31] Michael Ashikhmin. Synthesizing natural textures. ACM Symposium on Interactive 3D Graphics, 2001, pp. 217-226.
[32] 徐晓刚，于金辉，马利庄．多种子快速纹理合成．中国图形图像学报．Vol．7，No．10，2002，pp．995-999．
[33] Alexei A. Efros, William T. Freeman. Image Quilting for Texture Synthesis and Transfer. Computer Graphics Proceedings, Annual Conference Series, August 2001.
[34] Efros Alexei A, Leung Thomas K. Texture synthesis by non-parametric sampling. International Conference on Computer Vision, Greece:IEEE press, 1999:1033-1038 [30]
[35] 徐晓刚．纹理合成技术研究．浙江大学博士后研究工作报告．2001．11．
[36] Lin Liang, Ce Liu, Ying-Qing Xu, Baining Guo, and Heung-Yeung Shum. Real-Time Texture Synthesis By Patch-Based Sampling. ACM Transactions on Graphics. Vol. 20, No. 3, July 2001, pp. 127-150 .
[37] 和平鸽工作室，OpenGL高级编程与渲染系统开发，中国水利水电出版社，2003．1．
© 2004-2018 中国地质图书馆版权所有 京ICP备05064691号 京公网安备11010802017129号 地址：北京市海淀区学院路29号 邮编：100083 电话：办公室：(+86 10)66554848；文献借阅、咨询服务、科技查新：66554700 |