视景仿真中树木和地形可视化有关问题的研究与实现
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摘要
树木和地形的可视化研究是当前视景仿真领域研究的热点。如何在绘制质量和绘制速度这对矛盾中找到一个平衡点,是该领域研究的重要内容和目标。
在树木可视化方面,本文首先研究了已有的主要算法,包括分形理论中的L-系统法、迭代函数系统法和粒子系统模型法;以及基于图像的树木绘制方法,包括Billboard模型及其变体和层次纹理映射模型。比较了这些方法的优缺点和适用场合。
在综合比较已有树木算法的基础上,提出了在HSV色彩空间中基于图像的层次感树木可视化方法。该方法针对二维树木图像,利用HSV色彩空间对其进行分层提取处理,提取出若干层带有伪深度信息的图像,然后再将这些图像进行叠置、融合,构建出具有一定层次感立体效果的树木可视化模型。经实验验证,该方法建立的模型预处理过程简单省时,显示效果良好,具有一定的应用价值。
在地形可视化方面,本文介绍了基于Heightmap的地形绘制的基本方法,以及生成Heightmap的两种算法,即断层生成法和中点位移法。在此基础上,开展了基于LOD的地形可视化技术的应用与实现。重点研究了基于Geomipmapping和基于四叉树的LOD算法的原理与实现。探讨并解决了实现过程中存在的裂缝、节点评价和视景体裁剪等问题。实验结果表明,地形绘制的真实度高,能够展现出一定的LOD效果,同时满足实时性要求,具有广泛的应用价值。
Visualization of trees and terrain has become a research focus in present scene simulation, in which how to balance the quality and speed of rendering is one of the important topics of the research.
In aspect of trees visualization, some current typical algorithms of tree visualization are firstly studied, including L-system, Iteration function system and Particle system in Fractal theory as well as Billboard and its variants and Layered texture mapping model based on Image-based rendering (IBR). Meanwhile, advantages and disadvantages as well as applicable situations of these algorithms are compared.
On the basis of analysis and comparison of the existing algorithms, a new visualization method of trees using HSV color space based on IBR is presented. This method focuses on 2D tree image. Firstly, several sets of different color information, which is called as pseudo-depth information, are extracted in HSV color space from one image of tree. A few images, each of which is composed of the set of extracted color information, therefore are obtained. Finally, the images are arranged in specific distance in Euclidean Space to create the depth feeling in displaying. The experiment demonstrates that the visualization method of tree is simple and time-saving, and the effect is good and applicable.
In aspect of terrain visualization, the fundamental methods of terrain rendering based on Heightmap are introduced, and two methods of Heightmap generation, such as Fault formation and Midpoint displacement, are described as well. The principle and realization of LOD algorithms based on Geomipmapping and Quadtree are especially discussed, and the application and implementation of these methods are developed accordingly. Some existing problems in the process of implementation, such as cracks precaution, nodes evaluation, view frustum culling and so on, are investigated and solved. The running results offer a strong sense of reality and certain effect of LOD, and demonstrate that the terrain visualization methods mentioned above are capable of meeting the real-time requirements and are applicable for scene simulation.
在树木可视化方面,本文首先研究了已有的主要算法,包括分形理论中的L-系统法、迭代函数系统法和粒子系统模型法;以及基于图像的树木绘制方法,包括Billboard模型及其变体和层次纹理映射模型。比较了这些方法的优缺点和适用场合。
在综合比较已有树木算法的基础上,提出了在HSV色彩空间中基于图像的层次感树木可视化方法。该方法针对二维树木图像,利用HSV色彩空间对其进行分层提取处理,提取出若干层带有伪深度信息的图像,然后再将这些图像进行叠置、融合,构建出具有一定层次感立体效果的树木可视化模型。经实验验证,该方法建立的模型预处理过程简单省时,显示效果良好,具有一定的应用价值。
在地形可视化方面,本文介绍了基于Heightmap的地形绘制的基本方法,以及生成Heightmap的两种算法,即断层生成法和中点位移法。在此基础上,开展了基于LOD的地形可视化技术的应用与实现。重点研究了基于Geomipmapping和基于四叉树的LOD算法的原理与实现。探讨并解决了实现过程中存在的裂缝、节点评价和视景体裁剪等问题。实验结果表明,地形绘制的真实度高,能够展现出一定的LOD效果,同时满足实时性要求,具有广泛的应用价值。
Visualization of trees and terrain has become a research focus in present scene simulation, in which how to balance the quality and speed of rendering is one of the important topics of the research.
In aspect of trees visualization, some current typical algorithms of tree visualization are firstly studied, including L-system, Iteration function system and Particle system in Fractal theory as well as Billboard and its variants and Layered texture mapping model based on Image-based rendering (IBR). Meanwhile, advantages and disadvantages as well as applicable situations of these algorithms are compared.
On the basis of analysis and comparison of the existing algorithms, a new visualization method of trees using HSV color space based on IBR is presented. This method focuses on 2D tree image. Firstly, several sets of different color information, which is called as pseudo-depth information, are extracted in HSV color space from one image of tree. A few images, each of which is composed of the set of extracted color information, therefore are obtained. Finally, the images are arranged in specific distance in Euclidean Space to create the depth feeling in displaying. The experiment demonstrates that the visualization method of tree is simple and time-saving, and the effect is good and applicable.
In aspect of terrain visualization, the fundamental methods of terrain rendering based on Heightmap are introduced, and two methods of Heightmap generation, such as Fault formation and Midpoint displacement, are described as well. The principle and realization of LOD algorithms based on Geomipmapping and Quadtree are especially discussed, and the application and implementation of these methods are developed accordingly. Some existing problems in the process of implementation, such as cracks precaution, nodes evaluation, view frustum culling and so on, are investigated and solved. The running results offer a strong sense of reality and certain effect of LOD, and demonstrate that the terrain visualization methods mentioned above are capable of meeting the real-time requirements and are applicable for scene simulation.
引文
[1]曾芬芳.虚拟现实技术[M].上海:上海交通大学出版社,1997
[2]Cai Yiyu,Chui C,Ye Xiuzi,et al.VR Simulated Training for Less Invasive Vascular Intervention[J].Computers & Graphics,2003,27(2):215-221
[3]Jayaram S,Connacher H I,Lyons K W.Virtual Assembly Using Virtual Reality Techniques[J].Computer-Aided Design,1997,29(8):575-584
[4]Trika S N,Banerjee P,Kashyap R L.Virtual Reality Interfaces for Feature-based Computer-aided Design Systems[J].Computer-Aided Design,1997,29(8):565-574
[5]Nobuto M P.Toposal of A New Medical Manipulator for Laparoscopic Surgery[J].Advanced Robotics,2001,15(3):379-382
[6]贾连兴.仿真技术与软件[M].北京:国防工业出版社,2007
[7]王子才.仿真技术发展及应用[J].中国工程科学,2002,5(2):40-44
[8]蒋赞平,谢道奎.仿真与国民经济[J].系统仿真学报,2001,13(1):14-17
[9]孙敏.树模型的三维可视化研究[J].遥感学报,2002,6(3):188-192
[10]龙洁,苏喜友.国内树木三维可视化技术研究进展[J].林业机械与木工设备,2007,6:4-6
[11]Katsuhiko Onishi,Shoichi Hasuike,Yoshifumi Kitamura,Fumio Kishino.Interactive Modeling of Trees by Using Growth Simulation[J].ACM VRST'03,October 1-3,2003
[12]Dieter Schmalstieg,Michael Gervautz,.Modeling and Rendering of Outdoor Scenes for Distributed Virtual Environments[J].ACM VRST'97
[13]Soner I.Sen,A.M.Day.Modelling Trees and Their Tnteraction with the Environment:A survey[J].Computers & Graphics,2005,29:805-817
[14]严涛,吴恩华.基于多幅图象的植物造型方法[J].系统仿真学报,2000,12(5):565-571
[15]刘彦宏,王洪斌.基于图像的树类物体的三维重建[J].计算机学报,2002,25(5):930-935
[16]Alex Reche,Ignacio Martin,George Drettakis.Volumetric Reconstruction and Interactive Rendering of Trees from Photographs[J].ACM VRST'04:720-727
[17]靳海亮,康建荣,高井祥.基于VC和OpenGL生成三维真实感地形[J].舰船电子工程,2005,2:102-106
[18]曹为刚.基于OpenGL的三维地形的可视化技术与实现[J].海洋地质动态,2006,22(1):34-37
[19]孙敏,薛勇,马蔼乃.基于格网划分的大数据集DEM三维可视化[J].计算机辅助设计与图形学学报,2002,14(6):566-570
[20]Hugnes Hoppe.Smooth View-Dependent Level-of-Detail Control and its Application to Terrain Rendering[J].Microsoft Research,IEEE Visualization 1998:35-42
[21]Baoquan Chen,J.Edward Swan Ⅱ,Eddy Kuo,Arie Kaufman.LOD-Sprite Technique for Accelerated Terrain Rendering[J].Proceedings IEEE Visualization '99:291-298
[22]陈斌.基于OpenGL的抓取机械手的建模和动态仿真研究[D].北京:北京化工大学,2008
[23]乔林,费广正.OpenGL程序设计[M].北京:清华大学出版社,2000
[24]孙博文.分形算法与程序设计:用Visual C++实现[M].北京:科学出版社,2004
[25]芮小平,杨崇俊,程起敏.3维场景中树的一种简易绘制方法[J].测绘通报,2002,3:61-62
[26]Xavier Decoret,Fredo Durand,Francois X.Sillion,Julie Dorsey.Billboard Clouds for Extreme Model simplification[A].In:Proceedings of ACM SIGGRAPH 2003[C],New York:ACM Press,2003:689-696
[27]张淮声,华炜,王青,鲍虎军.层次深度拼图集:一种新的树木快速绘制方法[J].中国图像图形学报,2004,9(10):1216-1221
[28]齐东旭.分形及其计算机生成.科学出版社[M].北京:科学出版社,1994
[29]孙艳,刘弘.基于L系统的植物形态模拟研究[J].信息技术与信息化,2007,5:80-81
[30]张黎明.IFS理论在自然景物模拟中的应用[D].陕西:西安电子科技大学,2005
[31]William T Reeves.Particle System—A technique for modeling a class of fuzzy objects [J].SIGGRAPH'83,Computer Graphics,1983,17(3):359-376
[32]王小铭,林拉.树木模拟的粒子系统模型及其实现[J].华南师范大学学报(自然科学版),2003,3:49-53
[33]王小铭.基于粒子系统方法的树木形态结构模拟[J].工程图学学报,2001(增刊):401-402
[34]Andrew Lippman.Movie Maps:An Application of the Optical Videodisc to Computer Graphics[A].In:Proceedings of ACM SIGGRAPH 1980[C],New York:ACM Press,1980:32-43
[35]向世明.OpenGL编程与实例[M].北京:电子工业出版社,1999
[36]吕希奎,韩峰,韩春华.线路三维仿真系统中对称物的简易绘制方法[J].兰州交通大学学报(自然科学版),2004,23(6):30-33
[37]Anton Fuhrmann,Eike Umlauf,Stephan Mantler.Extreme Model Simplification for Forest Rendering.VRVis Virtual and Visualization Research Center.2004
[38]郑新,王文成,吴恩华.运用层次纹理映射的基于图像绘制算法[J].软件学报,2001,12(11):1647-1653
[39]Shade J,Gortler S,He L,et al.Layered Depth Images[A].In:Proceedings of ACM SIGGRAPH 1998[C],New York:ACM Press,1998:231-243
[40]Jason Weber,Joseph Penn.Creation and Rendering of Realistic Trees[A].In:Proceedings of ACM SIGGRAPH 1995[C],New York:ACM Press,1995:119-128
[41]丁海波,薛质,李生红.基于HSI空间的肤色检测方法[J].计算机应用,2004,24:210-211
[42]齐敏,郝重阳,佟明安.三维地形生成及实时显示技术研究进展[J].中国图像图形学报,2000,5(4):269-275
[43]Trent Polaek.Focus on 3D Terrain Programming[M].Premier Press,2003
[44]Jason Shankel.Fractal Terrain Generation--Fault Formation.In:Game Programming Gems[M].Rockland,Massachusetts:Charles River Media,2000
[45]任远红.基于LOD的地形算法的研究[D].湖北:武汉理工大学,2007
[46]万定生,龚汇丰.大规模地形的LOD生成算法研究[J].计算机工程与设计,2007,28(22):5345-5348
[47]曹敏,杨长兴,杨炼.大规模地形漫游中动态LOD算法研究[J].计算机技术与发展,2008,18(10):187-193
[48]王臻.多分辨率LOD地形建模及简化技术研究[D].安徽:合肥工业大学,2007
[49]张玲玲,王家海,成遣等.基于四又树的LOD地形简化研究[J].辽宁工程技术大学学报,2004,23(6):814-815
[50]Stefan R,Wolfgang H,Philipp S,et al.Real-time Generation of Continuous Levels of Detail for Height Fields[A].In:Proceedings of the 6th International Conference in Central European Computer Graphics and Visualization 1998[C],Plzen,Czech Republic:315-322
[51]王臻,胡敏,李响.基于四叉树的动态多分辨率LOD地形快速简化[J].计算机应用,2007,27(7):1641-1643
[52]杨崇源,张继贤,林宗坚.虚拟地形场景绘制中的实时LOD算法[J].测绘学报,2001,30(2):133-139
[2]Cai Yiyu,Chui C,Ye Xiuzi,et al.VR Simulated Training for Less Invasive Vascular Intervention[J].Computers & Graphics,2003,27(2):215-221
[3]Jayaram S,Connacher H I,Lyons K W.Virtual Assembly Using Virtual Reality Techniques[J].Computer-Aided Design,1997,29(8):575-584
[4]Trika S N,Banerjee P,Kashyap R L.Virtual Reality Interfaces for Feature-based Computer-aided Design Systems[J].Computer-Aided Design,1997,29(8):565-574
[5]Nobuto M P.Toposal of A New Medical Manipulator for Laparoscopic Surgery[J].Advanced Robotics,2001,15(3):379-382
[6]贾连兴.仿真技术与软件[M].北京:国防工业出版社,2007
[7]王子才.仿真技术发展及应用[J].中国工程科学,2002,5(2):40-44
[8]蒋赞平,谢道奎.仿真与国民经济[J].系统仿真学报,2001,13(1):14-17
[9]孙敏.树模型的三维可视化研究[J].遥感学报,2002,6(3):188-192
[10]龙洁,苏喜友.国内树木三维可视化技术研究进展[J].林业机械与木工设备,2007,6:4-6
[11]Katsuhiko Onishi,Shoichi Hasuike,Yoshifumi Kitamura,Fumio Kishino.Interactive Modeling of Trees by Using Growth Simulation[J].ACM VRST'03,October 1-3,2003
[12]Dieter Schmalstieg,Michael Gervautz,.Modeling and Rendering of Outdoor Scenes for Distributed Virtual Environments[J].ACM VRST'97
[13]Soner I.Sen,A.M.Day.Modelling Trees and Their Tnteraction with the Environment:A survey[J].Computers & Graphics,2005,29:805-817
[14]严涛,吴恩华.基于多幅图象的植物造型方法[J].系统仿真学报,2000,12(5):565-571
[15]刘彦宏,王洪斌.基于图像的树类物体的三维重建[J].计算机学报,2002,25(5):930-935
[16]Alex Reche,Ignacio Martin,George Drettakis.Volumetric Reconstruction and Interactive Rendering of Trees from Photographs[J].ACM VRST'04:720-727
[17]靳海亮,康建荣,高井祥.基于VC和OpenGL生成三维真实感地形[J].舰船电子工程,2005,2:102-106
[18]曹为刚.基于OpenGL的三维地形的可视化技术与实现[J].海洋地质动态,2006,22(1):34-37
[19]孙敏,薛勇,马蔼乃.基于格网划分的大数据集DEM三维可视化[J].计算机辅助设计与图形学学报,2002,14(6):566-570
[20]Hugnes Hoppe.Smooth View-Dependent Level-of-Detail Control and its Application to Terrain Rendering[J].Microsoft Research,IEEE Visualization 1998:35-42
[21]Baoquan Chen,J.Edward Swan Ⅱ,Eddy Kuo,Arie Kaufman.LOD-Sprite Technique for Accelerated Terrain Rendering[J].Proceedings IEEE Visualization '99:291-298
[22]陈斌.基于OpenGL的抓取机械手的建模和动态仿真研究[D].北京:北京化工大学,2008
[23]乔林,费广正.OpenGL程序设计[M].北京:清华大学出版社,2000
[24]孙博文.分形算法与程序设计:用Visual C++实现[M].北京:科学出版社,2004
[25]芮小平,杨崇俊,程起敏.3维场景中树的一种简易绘制方法[J].测绘通报,2002,3:61-62
[26]Xavier Decoret,Fredo Durand,Francois X.Sillion,Julie Dorsey.Billboard Clouds for Extreme Model simplification[A].In:Proceedings of ACM SIGGRAPH 2003[C],New York:ACM Press,2003:689-696
[27]张淮声,华炜,王青,鲍虎军.层次深度拼图集:一种新的树木快速绘制方法[J].中国图像图形学报,2004,9(10):1216-1221
[28]齐东旭.分形及其计算机生成.科学出版社[M].北京:科学出版社,1994
[29]孙艳,刘弘.基于L系统的植物形态模拟研究[J].信息技术与信息化,2007,5:80-81
[30]张黎明.IFS理论在自然景物模拟中的应用[D].陕西:西安电子科技大学,2005
[31]William T Reeves.Particle System—A technique for modeling a class of fuzzy objects [J].SIGGRAPH'83,Computer Graphics,1983,17(3):359-376
[32]王小铭,林拉.树木模拟的粒子系统模型及其实现[J].华南师范大学学报(自然科学版),2003,3:49-53
[33]王小铭.基于粒子系统方法的树木形态结构模拟[J].工程图学学报,2001(增刊):401-402
[34]Andrew Lippman.Movie Maps:An Application of the Optical Videodisc to Computer Graphics[A].In:Proceedings of ACM SIGGRAPH 1980[C],New York:ACM Press,1980:32-43
[35]向世明.OpenGL编程与实例[M].北京:电子工业出版社,1999
[36]吕希奎,韩峰,韩春华.线路三维仿真系统中对称物的简易绘制方法[J].兰州交通大学学报(自然科学版),2004,23(6):30-33
[37]Anton Fuhrmann,Eike Umlauf,Stephan Mantler.Extreme Model Simplification for Forest Rendering.VRVis Virtual and Visualization Research Center.2004
[38]郑新,王文成,吴恩华.运用层次纹理映射的基于图像绘制算法[J].软件学报,2001,12(11):1647-1653
[39]Shade J,Gortler S,He L,et al.Layered Depth Images[A].In:Proceedings of ACM SIGGRAPH 1998[C],New York:ACM Press,1998:231-243
[40]Jason Weber,Joseph Penn.Creation and Rendering of Realistic Trees[A].In:Proceedings of ACM SIGGRAPH 1995[C],New York:ACM Press,1995:119-128
[41]丁海波,薛质,李生红.基于HSI空间的肤色检测方法[J].计算机应用,2004,24:210-211
[42]齐敏,郝重阳,佟明安.三维地形生成及实时显示技术研究进展[J].中国图像图形学报,2000,5(4):269-275
[43]Trent Polaek.Focus on 3D Terrain Programming[M].Premier Press,2003
[44]Jason Shankel.Fractal Terrain Generation--Fault Formation.In:Game Programming Gems[M].Rockland,Massachusetts:Charles River Media,2000
[45]任远红.基于LOD的地形算法的研究[D].湖北:武汉理工大学,2007
[46]万定生,龚汇丰.大规模地形的LOD生成算法研究[J].计算机工程与设计,2007,28(22):5345-5348
[47]曹敏,杨长兴,杨炼.大规模地形漫游中动态LOD算法研究[J].计算机技术与发展,2008,18(10):187-193
[48]王臻.多分辨率LOD地形建模及简化技术研究[D].安徽:合肥工业大学,2007
[49]张玲玲,王家海,成遣等.基于四又树的LOD地形简化研究[J].辽宁工程技术大学学报,2004,23(6):814-815
[50]Stefan R,Wolfgang H,Philipp S,et al.Real-time Generation of Continuous Levels of Detail for Height Fields[A].In:Proceedings of the 6th International Conference in Central European Computer Graphics and Visualization 1998[C],Plzen,Czech Republic:315-322
[51]王臻,胡敏,李响.基于四叉树的动态多分辨率LOD地形快速简化[J].计算机应用,2007,27(7):1641-1643
[52]杨崇源,张继贤,林宗坚.虚拟地形场景绘制中的实时LOD算法[J].测绘学报,2001,30(2):133-139