ChunkedLOD—海量地形的实时绘制系统
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摘要
地形的实时绘制在很多游戏和仿真应用中有着非常重要的地位。随着计算机硬件的不断发展和算法的不断改进，我们绘制真实感地形的能力在不断地提高。近年来，随着图形处理芯片(Graphic Processing Unit，GPU)的出现和普及，显卡逐渐成为一个强大的可独立编程控制的设备。变换和光照(Transform & Lighting)、立方环境材质贴图(Cubic Environment Maps)、顶点混合(Vertex Blending)、纹理压缩(Texture Compression)和凹凸映射贴图(Bump Mapping)、双重纹理(Dual Texture)四像素256位渲染等均可以在GPU中完成，大大减轻了CPU的压力，对实时图形渲染产生了深远的影响，这其中包括实时地形渲染。另外，随着遥感技术，卫星技术的发展，使得获得高分辨率的数字几何高程数据以及影像纹理数据成为可能，人们希望观察更广范围更为精细的地形，在许多应用中，地形数据集太大而无法全部容于内存之中，可以称之为海量(out of core)，这就对地形的实时绘制提出了更高的要求。
本文提出了一个有效的，硬件友好的基于外存的海量地形数据实时可视化框架—Chunked LOD。该框架有效地融合了地形的连续细节层次模型和纹理的多分辨率表示。无论是几何数据还是纹理数据均进行了多分辨率组织，并且根据它们在屏幕空间的简化误差实时选取两者恰当的分辨率。该框架还有效地利用了nVIDIA的OpenGL扩展GL_NV_vertex_array_range和GL_NV_fence来对场景的渲染进行加速。它们能够让几何图形高效地传输到GPU，GPU直接访问顶点数据，使得应用程序的执行效率极大提高。
本文第一章简单地介绍了地形实时绘制的应用背景和一些基本概念，对目前这一领域中已有的一些经典算法分别作了综述，并对它们进行了比较。
本文第二章详细地介绍了海量地形实时绘制过程中各种问题的解决方法。提出了一个有效的，硬件友好的海量地形实时绘制框架—Chunked LOD。
本文第三章描述了海量地形绘制系统—Chunked LOD的组织结构和实现细节，同时给出了部分示例程序和地形绘制的运行结果，并对地形绘制的未来研究方向做了预测。
Real time terrain rendering is an important technology for a large class of applications, such as game and simulation. Hardware and algorithms are being improved rapidly, which enhances our ability to render realistic terrains. In recent year, in consumer hardware, there is a trend to shift the CPU-bound graphics processing capability to high speed special purpose graphics processing units (CPU's ). This trend has drastically changed the algorithms in terrain LOD rendering, and sparkled the development of GPU-oriented aggregated LOD algorithms. Furthermore, by using the database with increased quantity and details need to handle the datasets which do not fit in RAM (out-of-core datasets ). Meanwhile, advances in shading and image quality in general have raised the bar for image quality we would like to achieve in terrain rendering a
In this thesis, we propose an efficient hardware-friendly framework-Chunked LOD, for large-scale terrain real-time rendering .Within this framework, the approach for integrating multi-resolution representations of terrain geometry and terrain texture data is presented. In our framework, the multi-resolution models for terrain texture data and geometry data are matched with each other to achieve the goal of real time rendering.
In Chapter 1, we introduce some backgrounds and application domains of the real-time terrain rendering. Meanwhile, we summarize some typical methods in recent publications, and enumerate and discuss the research works about terrain rendering in recent years.
In Chapter 2, we discuss the terrain modeling with continuous level of detail, described a data layout technique for manage out-of-core datasets.Then, we investigate the OpenGL based NV extension for fully taking advantage of the accelerating function of graphic hardware and improving the capability of rendering. At last, we present an efficient hardware-friendly framework-Chunked LOD for large-scale terrain real-time rendering.
In Chapter 3, we described the implementation of the Chunked LOD-an efficient, hard ware-friendly framework for large-scale terrain real-time visualization. And the future trends in real-time terrain rendering are disscussed.
本文提出了一个有效的，硬件友好的基于外存的海量地形数据实时可视化框架—Chunked LOD。该框架有效地融合了地形的连续细节层次模型和纹理的多分辨率表示。无论是几何数据还是纹理数据均进行了多分辨率组织，并且根据它们在屏幕空间的简化误差实时选取两者恰当的分辨率。该框架还有效地利用了nVIDIA的OpenGL扩展GL_NV_vertex_array_range和GL_NV_fence来对场景的渲染进行加速。它们能够让几何图形高效地传输到GPU，GPU直接访问顶点数据，使得应用程序的执行效率极大提高。
本文第一章简单地介绍了地形实时绘制的应用背景和一些基本概念，对目前这一领域中已有的一些经典算法分别作了综述，并对它们进行了比较。
本文第二章详细地介绍了海量地形实时绘制过程中各种问题的解决方法。提出了一个有效的，硬件友好的海量地形实时绘制框架—Chunked LOD。
本文第三章描述了海量地形绘制系统—Chunked LOD的组织结构和实现细节，同时给出了部分示例程序和地形绘制的运行结果，并对地形绘制的未来研究方向做了预测。
Real time terrain rendering is an important technology for a large class of applications, such as game and simulation. Hardware and algorithms are being improved rapidly, which enhances our ability to render realistic terrains. In recent year, in consumer hardware, there is a trend to shift the CPU-bound graphics processing capability to high speed special purpose graphics processing units (CPU's ). This trend has drastically changed the algorithms in terrain LOD rendering, and sparkled the development of GPU-oriented aggregated LOD algorithms. Furthermore, by using the database with increased quantity and details need to handle the datasets which do not fit in RAM (out-of-core datasets ). Meanwhile, advances in shading and image quality in general have raised the bar for image quality we would like to achieve in terrain rendering a
In this thesis, we propose an efficient hardware-friendly framework-Chunked LOD, for large-scale terrain real-time rendering .Within this framework, the approach for integrating multi-resolution representations of terrain geometry and terrain texture data is presented. In our framework, the multi-resolution models for terrain texture data and geometry data are matched with each other to achieve the goal of real time rendering.
In Chapter 1, we introduce some backgrounds and application domains of the real-time terrain rendering. Meanwhile, we summarize some typical methods in recent publications, and enumerate and discuss the research works about terrain rendering in recent years.
In Chapter 2, we discuss the terrain modeling with continuous level of detail, described a data layout technique for manage out-of-core datasets.Then, we investigate the OpenGL based NV extension for fully taking advantage of the accelerating function of graphic hardware and improving the capability of rendering. At last, we present an efficient hardware-friendly framework-Chunked LOD for large-scale terrain real-time rendering.
In Chapter 3, we described the implementation of the Chunked LOD-an efficient, hard ware-friendly framework for large-scale terrain real-time visualization. And the future trends in real-time terrain rendering are disscussed.
引文
[Lindstrom 95] Lindstrom, P. and Koller, D. and Hodges, L.F. and Ribarsky, W. and Faust, N. and Turner, G. Level-of-Detail Management for Real-time Rendering of Phototextured Terrain, Technical report GIT-GVU-95-06, January 1995
[Evans 96] Francine Evans, Steven S. Skiena, and Amitabh.Varshney, Optimizing Triangle Strips for Fast Rendering, IEEE Visualization'96, 319～326, Oct 1996
[Lindstrom 96] Lindstrom, P. and Koller D. and Ribarsky, W. and Hodges, L.F. and Faust, N. and Turner, G.A. Real-Time, Continuous Level of Detail Rendering of Height Fields, Proceedings of ACM SIGGRAPH 96, August 1996, pp. 109-118
[Duchaineau 97] Duchaineau, M. and Wolinsky, M. and Sigeti, D.E. and Miller, M.C. and Aldrich, C. and Mineev-Weinstein, M.B. ROAMing Terrain: Real-time Optimally Adapting Meshes, Proceedings of Visualization 1997, pp. 81-88
[Evans 97] William Evans, David Kirkpatrick, and Gregg Townsend, Right Triangulated Irregular Networks, Technical Report 97-09, University of Arizona, May
[Hoppe 98] Hoppe, H. Smooth view-dependent level-of-detail control and its application to terrain rendering, IEEE Visualization 1998, October 1998, page 35-42
[Rttger 98] Rttger, S. and Heidrich, W. and Slusalleck, P. and Seidel, H.P. Real-Time Generation of Continuous Levels of Detail for Height Fields, V. Skala, editor, Proceedings of WSCG'98, pages 315-322, 1998
[Reddy 99] Reddy, M. and Lecerc, Y.G. and Iverson, L. and Bletter, N. TerraVision Ⅱ: Visualizing Massive Terrain Databases in VRML, IEEE Computer Graphics and Applications. Vol. 19(2), 1999, pp. 30-38
[Jonathan 2000] Jonathan Blow, Terrain Rendering at High Levels of Detail, paper for the Game Developers' Conference 2000, San Jose, California, USA, March 11, 2000
[Ulrich 2000] Ulrich Thatcher. Continuous LOD Terrain Meshing Using Adaptive Quadtrees. GameSutra. 2000. http://www.gamasutra.com/features/20000228/ulrich_01.htm
[DeFloriani 2000] DeFloriani, L. and Magillo, P. and Puppo, E. VARIANT: A System for Terrain Modeling at Variable Resolution. Geolnformatica. Vol. 4(3). 2000. pp. 287-315
[Corpes 2001] Corpes, G., Procedural Landscapes, presentation at GDC 2001
[Hakl 2001] Henri Hakl, Diamond Terrain Algorithm: CLOD for Height Fieds, Honors Year Project, University of Stellenbosch, 2001
[Lindstrom 2001] Lindstrom, P. and Pascucci, V. Visualization of Large Terrains Made Easy, Proceedings of Visualization 2001, pp. 363-370
[Ulrich 2002] Thatcher Ulrich, Rendering Massive Terrains using Chunked Level of Detail Control, SIGGRAPH 2002, course 35
[Larsen 2003] B.D. Larsen, N. J. Christensen, Real-time Terrain Rendering using Smooth Hardware Optimized Level of Detail, WSCG'2003, February 3-7, 2003
[VTP] Ben Discoe, http://www.vterrain.org/ This web site is an excellent survey of algorithms, implementations, tools and techniques related to terrain rendering
Seumas McNally. http://www.longbowdigitalarts.com/seumas/progbintri.html This is a good practical introduction to Binary Triangle Trees from [3]. Also see http://www.treadmarks.com/a game which uses methods from [3]
J.Dǒ llner, K. Baumann, and K. Hinrichs. Texturing Techniques for Terrain Visualization. IEEE Visualization 2000, 207-234. Oct. 2000
J.S. Vitter. External Memory Algorithms and Data Structures: Dealing with MASSIVE DATA. ACM Computing Surveys, 2001.
陈刚 虚拟地形环境的层次描述与实时渲染技术研究[D]，郑州，解放军信息工程大学测绘学院，2000
王宏武，董士海 一个视点相关的动态多分辨率地形模型[J]，计算机辅助设计与图形学学报，2000，12(8)：575～579
谭兵 2001 基于遥感影像的地形三维重建技术的研究[D]，郑州，解放军信息工程大学测绘学院，2001
谭兵 2003 大区域可视化技术的研究，中国图象图形学报，2003，5(8)，578～584
陆艳青 海量数据地形实时绘制的地形研究[D]，杭州，浙江大学CAD&CG国家重点实验室，2003
[Evans 96] Francine Evans, Steven S. Skiena, and Amitabh.Varshney, Optimizing Triangle Strips for Fast Rendering, IEEE Visualization'96, 319～326, Oct 1996
[Lindstrom 96] Lindstrom, P. and Koller D. and Ribarsky, W. and Hodges, L.F. and Faust, N. and Turner, G.A. Real-Time, Continuous Level of Detail Rendering of Height Fields, Proceedings of ACM SIGGRAPH 96, August 1996, pp. 109-118
[Duchaineau 97] Duchaineau, M. and Wolinsky, M. and Sigeti, D.E. and Miller, M.C. and Aldrich, C. and Mineev-Weinstein, M.B. ROAMing Terrain: Real-time Optimally Adapting Meshes, Proceedings of Visualization 1997, pp. 81-88
[Evans 97] William Evans, David Kirkpatrick, and Gregg Townsend, Right Triangulated Irregular Networks, Technical Report 97-09, University of Arizona, May
[Hoppe 98] Hoppe, H. Smooth view-dependent level-of-detail control and its application to terrain rendering, IEEE Visualization 1998, October 1998, page 35-42
[Rttger 98] Rttger, S. and Heidrich, W. and Slusalleck, P. and Seidel, H.P. Real-Time Generation of Continuous Levels of Detail for Height Fields, V. Skala, editor, Proceedings of WSCG'98, pages 315-322, 1998
[Reddy 99] Reddy, M. and Lecerc, Y.G. and Iverson, L. and Bletter, N. TerraVision Ⅱ: Visualizing Massive Terrain Databases in VRML, IEEE Computer Graphics and Applications. Vol. 19(2), 1999, pp. 30-38
[Jonathan 2000] Jonathan Blow, Terrain Rendering at High Levels of Detail, paper for the Game Developers' Conference 2000, San Jose, California, USA, March 11, 2000
[Ulrich 2000] Ulrich Thatcher. Continuous LOD Terrain Meshing Using Adaptive Quadtrees. GameSutra. 2000. http://www.gamasutra.com/features/20000228/ulrich_01.htm
[DeFloriani 2000] DeFloriani, L. and Magillo, P. and Puppo, E. VARIANT: A System for Terrain Modeling at Variable Resolution. Geolnformatica. Vol. 4(3). 2000. pp. 287-315
[Corpes 2001] Corpes, G., Procedural Landscapes, presentation at GDC 2001
[Hakl 2001] Henri Hakl, Diamond Terrain Algorithm: CLOD for Height Fieds, Honors Year Project, University of Stellenbosch, 2001
[Lindstrom 2001] Lindstrom, P. and Pascucci, V. Visualization of Large Terrains Made Easy, Proceedings of Visualization 2001, pp. 363-370
[Ulrich 2002] Thatcher Ulrich, Rendering Massive Terrains using Chunked Level of Detail Control, SIGGRAPH 2002, course 35
[Larsen 2003] B.D. Larsen, N. J. Christensen, Real-time Terrain Rendering using Smooth Hardware Optimized Level of Detail, WSCG'2003, February 3-7, 2003
[VTP] Ben Discoe, http://www.vterrain.org/ This web site is an excellent survey of algorithms, implementations, tools and techniques related to terrain rendering
Seumas McNally. http://www.longbowdigitalarts.com/seumas/progbintri.html This is a good practical introduction to Binary Triangle Trees from [3]. Also see http://www.treadmarks.com/a game which uses methods from [3]
J.Dǒ llner, K. Baumann, and K. Hinrichs. Texturing Techniques for Terrain Visualization. IEEE Visualization 2000, 207-234. Oct. 2000
J.S. Vitter. External Memory Algorithms and Data Structures: Dealing with MASSIVE DATA. ACM Computing Surveys, 2001.
陈刚 虚拟地形环境的层次描述与实时渲染技术研究[D]，郑州，解放军信息工程大学测绘学院，2000
王宏武，董士海 一个视点相关的动态多分辨率地形模型[J]，计算机辅助设计与图形学学报，2000，12(8)：575～579
谭兵 2001 基于遥感影像的地形三维重建技术的研究[D]，郑州，解放军信息工程大学测绘学院，2001
谭兵 2003 大区域可视化技术的研究，中国图象图形学报，2003，5(8)，578～584
陆艳青 海量数据地形实时绘制的地形研究[D]，杭州，浙江大学CAD&CG国家重点实验室，2003
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