三维场景网上漫游的实时渲染技术研究与应用
摘要
在互动娱乐、古迹重现、模拟仿真和军事演练等领域,用户对身临其境的感觉的要求越来越高。与此同时,随着硬件设备能力的逐步提升,开发者也没有停止过对真实感技术的探索和实践。三维可漫游场景的表现力和沉浸感远胜于二维的表现形式,因此近些年针对三维漫游的实时渲染技术的研究成为热点。三维场景漫游的实时渲染技术不但是三维虚拟系统的核心技术,而且直接决定着用户的真实感体验。对于三维场景漫游的实时渲染技术,本文所做的主要工作及研究如下：
(1)针对大场景内物体渲染的排序问题,提出了一种基于渲染状态的渲染排序方法。首先,定义一个键值对结构,键存放的是材质信息,值存放的是物体信息。然后,解析材质脚本和物体信息并将其相应的属性填充到键(Key)的相应位。最后,分别按键的各个位所代表的意义对材质进行排序。
(2)针对大规模地形的渲染问题,提出了一种基于GPU的地形LOD算法。首先,使用四叉树数据结构来组织地形数据。然后,通过GPU顶点程序处理过渡区域,消除不同细节等级层次间的裂缝问题。最后,我们将四个单通道纹理元素打包成四通道纹理元素降低了低端图形卡在顶点程序采样高度纹理的消耗。
(3)针对北方工业大学虚拟校园实现过程中遇到的问题以及项目中的需求,对系统使用的场景加载策略、漫游方式、导航方式进行了介绍。最后展示了虚拟校园的部分主要功能。
In the scopes of entertainment, reproducing of historical site, simulating and military affairs, the users demand the feeling of immersing themselves in the virtual scene increasingly. At the same time, with the gradual upgrading of hardware equipment capacity, the software developers never stop exploring and practicing on the realistic technology. The expressive force and immersion in 3D roaming scene are much better than those in 2D scene, so the real-time rendering of 3D roaming become hotspot recent years. The real-time rendering of 3D roaming is not only the core technology in 3D virtual System, but also determines the realism the users experience directly, In this paper, the major work and research in real-time rendering of 3D scene roaming as follows:
(1)Focusing on the sorting of renderable objects in large scene, we propose a sorting method based on the rendering state. Firstly, we define a pair structure, the key is the material information and the value is the object information. And then we analyze the material script and the object information, and fill the key with the information. Finally, we sort the materials based on the meaning of each bit.
(2)Focusing on the rendering of large-scale terrain, we propose a GPU based LOD approach. Firstly, we use the quadtree structure to organize the terrain data. Secondly, we deal with the transition zone to eliminate the crack between meshes in different LOD by vertex program. Finally, we package four single-channel texels to a four-channel texel to reduce the consumption of low-end graphics card in sampling heightmap in vertex program.
(3)Focusing on the problems encountered and the project requirements in North China University of Technology Virtual Campus, we introduce the scene loading, roaming and navigation methods we use. Finally, demonstrates the major functions about NCUT Virtual Campus.
(1)针对大场景内物体渲染的排序问题,提出了一种基于渲染状态的渲染排序方法。首先,定义一个键值对结构,键存放的是材质信息,值存放的是物体信息。然后,解析材质脚本和物体信息并将其相应的属性填充到键(Key)的相应位。最后,分别按键的各个位所代表的意义对材质进行排序。
(2)针对大规模地形的渲染问题,提出了一种基于GPU的地形LOD算法。首先,使用四叉树数据结构来组织地形数据。然后,通过GPU顶点程序处理过渡区域,消除不同细节等级层次间的裂缝问题。最后,我们将四个单通道纹理元素打包成四通道纹理元素降低了低端图形卡在顶点程序采样高度纹理的消耗。
(3)针对北方工业大学虚拟校园实现过程中遇到的问题以及项目中的需求,对系统使用的场景加载策略、漫游方式、导航方式进行了介绍。最后展示了虚拟校园的部分主要功能。
In the scopes of entertainment, reproducing of historical site, simulating and military affairs, the users demand the feeling of immersing themselves in the virtual scene increasingly. At the same time, with the gradual upgrading of hardware equipment capacity, the software developers never stop exploring and practicing on the realistic technology. The expressive force and immersion in 3D roaming scene are much better than those in 2D scene, so the real-time rendering of 3D roaming become hotspot recent years. The real-time rendering of 3D roaming is not only the core technology in 3D virtual System, but also determines the realism the users experience directly, In this paper, the major work and research in real-time rendering of 3D scene roaming as follows:
(1)Focusing on the sorting of renderable objects in large scene, we propose a sorting method based on the rendering state. Firstly, we define a pair structure, the key is the material information and the value is the object information. And then we analyze the material script and the object information, and fill the key with the information. Finally, we sort the materials based on the meaning of each bit.
(2)Focusing on the rendering of large-scale terrain, we propose a GPU based LOD approach. Firstly, we use the quadtree structure to organize the terrain data. Secondly, we deal with the transition zone to eliminate the crack between meshes in different LOD by vertex program. Finally, we package four single-channel texels to a four-channel texel to reduce the consumption of low-end graphics card in sampling heightmap in vertex program.
(3)Focusing on the problems encountered and the project requirements in North China University of Technology Virtual Campus, we introduce the scene loading, roaming and navigation methods we use. Finally, demonstrates the major functions about NCUT Virtual Campus.
引文
[1]Arul Asirvatham, Hugues Hoppe. Terrain Rendering Using GPU-Based Geometry Clipmaps. GPU GEMS 2, Chapter 2.
[2]Rafael P.Torchelsen, Joao L.D.Comba, Rui Bastos. Practical Geometry Clipmaps for Rendering Terrains in Computer Games. ShaderX 6,103-114.
[3]Losasso, Frank, and Hugues Hoppe. Geometry Clipmaps:Terrain Rendering Using Nested Regular Grids. ACM Transactions on Graphics(Proceedings of SIGGRAPH 2004),2004. 23(3):769-776.
[4]Filip Strugar. Continuous Distance-Dependent Level of Detail for Rendering Heightmaps. Journal of graphics, gpu, and game tools,2009.14(4):57-74.
[5]Francesco Carucci. Inside Geometry Instancing. GPU Gems 2, Chapter 3.
[6]Wloka, Matthias. Batch, Batch, Batch:What Does It Really Mean. Game Developers Conference 2003. http://developer.nvidia.com/docs/IO/8230/Batch Batch Batch.pdf.
[7]周炜,葛娟,刘浏等.基于材质的实时渲染场景组织技术.计算机辅助设计与图形学学报,2009.21(6)：819-824.
[8]Maple.渲染状态管理.http://blog.csdn.net/duduliao/archive/2008/08/25/2827683.aspx.
[9]吴迪,黄文骞.虚拟现实技术的发展过程及研究现状.海洋测绘,2002.22(6)：15-17.
[10]L. Williams. Pyramidal Parametrics. ACM SIGGRAPH Computer Graphics, 1983.17(3):1-11.
[11]Mark Duchaineau, Murray Wolinsky, David E. Sigeti etc. ROAMing Terrain:Real-time Optimally Adapting Meshes. Los Alamos National Laboratory, Lawrence Livermore National Laboratory. http://www.llnl.gov/graphics/ROAM.
[12]Hugues Hoppe. Progressive meshes. SIGGRAPH'96 Proceedings of the 23 rd annual conference on Computer graphics and interactive techniques,1996:99-108.
[13]Andre LaMothe.3D Terrain Programming, Premier Press,2002:106-126.
[14]岳利群,游雄,夏青等.基于Clipmap的全球多分辨率可视化技术.测绘科学技术学报,2010,27(2)：131-134.
[15]Tanner, Christopher, Christopher Migdal etc. The Clipmap:A Virtual Mipmap. Computer Graphics(Proceeding of SIGGRAPH 98),1998:151-158.
[16]Gerasimov, Philip, Randima Fernando etc. Shader Model 3.0:Using Vertex Textures. Nvidia white paper DA-01373-001_v00,2004.
[17]宋永飞,艾力,罗亭.虚拟现实场景的漫游技术及其应用.内江师范学院学报,2010,25：416-417.
[18]Tomas Akenine-Moller, Eric Haines, Naty Hoffman. Real-Time Rendering 3rd. A K Peters. 2008.
[19]陈彦菲.校园内场景的虚拟漫游技术研究[硕士学位论文].大连：大连理工大学结构工程专业,2008.
[20]Jason Gregory. Game Engine Architecture. A K Peters.2009:197-259.
[21]王章野,陆艳青,彭群生.大规模场景的消隐技术.计算机工程与应用,2001,9：8-12.
[22]Christer Ericson. Real-Time Collision Detection. Elsevier.2005.
[23]刘波,王章野,王丽英等.大规模城市场景的高效建模及其实时绘制.计算机辅助设计与图形学学报,2008,20(9)：1153-1162.
[24]周昆,潘志庚,石教英.多细节层次模型间的平滑过渡.计算机辅助设计与图形学学报,2000,12(6)：463-467.
[25]周昆,潘志庚,石教英.基于三角形折叠的网格简化算法.计算机学报,1998,21(6)：506-514.
[26]J Cohen, M Olano, D Manocha. Appearance-preserving simplification. Computer Graphics (SIGGRAPH'98),1998,31:189-198.
[27]Alan Watt, Fabio Policarpo,3D Games Real-time Rendering and Software Technology. Pearson Education,2001.
[28]Lindstrom P and Turk G. Fast and memory efficient Polygonal simplification. IEEE Visualization'98 Conference Proeeedings,1998:279-286.
[29]Garland.M, Heekbert.P. Surface Simplification Using Quadric Error Metrics. Proceedings ofSIGGRAPH'97,1997:209-216.
[30]陈实.基于Web-3D的网络虚拟社区的交互设计.包装工程.2008.29(4)：84-86.
[31]周晓云,何大曾,刘慎权.一种层次模型构造方法.中国图像图形学报,1997,2(8)：556-561.
[32]Frank Luna. Introduction to 3D Game Programming with DirectX 9.0c:a shader approach. Wordware Publishing.2006.
[33]Frank Luna. Introduction to 3D Game Programming with DirectX 9.0. Wordware Publishing.2003.
[2]Rafael P.Torchelsen, Joao L.D.Comba, Rui Bastos. Practical Geometry Clipmaps for Rendering Terrains in Computer Games. ShaderX 6,103-114.
[3]Losasso, Frank, and Hugues Hoppe. Geometry Clipmaps:Terrain Rendering Using Nested Regular Grids. ACM Transactions on Graphics(Proceedings of SIGGRAPH 2004),2004. 23(3):769-776.
[4]Filip Strugar. Continuous Distance-Dependent Level of Detail for Rendering Heightmaps. Journal of graphics, gpu, and game tools,2009.14(4):57-74.
[5]Francesco Carucci. Inside Geometry Instancing. GPU Gems 2, Chapter 3.
[6]Wloka, Matthias. Batch, Batch, Batch:What Does It Really Mean. Game Developers Conference 2003. http://developer.nvidia.com/docs/IO/8230/Batch Batch Batch.pdf.
[7]周炜,葛娟,刘浏等.基于材质的实时渲染场景组织技术.计算机辅助设计与图形学学报,2009.21(6)：819-824.
[8]Maple.渲染状态管理.http://blog.csdn.net/duduliao/archive/2008/08/25/2827683.aspx.
[9]吴迪,黄文骞.虚拟现实技术的发展过程及研究现状.海洋测绘,2002.22(6)：15-17.
[10]L. Williams. Pyramidal Parametrics. ACM SIGGRAPH Computer Graphics, 1983.17(3):1-11.
[11]Mark Duchaineau, Murray Wolinsky, David E. Sigeti etc. ROAMing Terrain:Real-time Optimally Adapting Meshes. Los Alamos National Laboratory, Lawrence Livermore National Laboratory. http://www.llnl.gov/graphics/ROAM.
[12]Hugues Hoppe. Progressive meshes. SIGGRAPH'96 Proceedings of the 23 rd annual conference on Computer graphics and interactive techniques,1996:99-108.
[13]Andre LaMothe.3D Terrain Programming, Premier Press,2002:106-126.
[14]岳利群,游雄,夏青等.基于Clipmap的全球多分辨率可视化技术.测绘科学技术学报,2010,27(2)：131-134.
[15]Tanner, Christopher, Christopher Migdal etc. The Clipmap:A Virtual Mipmap. Computer Graphics(Proceeding of SIGGRAPH 98),1998:151-158.
[16]Gerasimov, Philip, Randima Fernando etc. Shader Model 3.0:Using Vertex Textures. Nvidia white paper DA-01373-001_v00,2004.
[17]宋永飞,艾力,罗亭.虚拟现实场景的漫游技术及其应用.内江师范学院学报,2010,25：416-417.
[18]Tomas Akenine-Moller, Eric Haines, Naty Hoffman. Real-Time Rendering 3rd. A K Peters. 2008.
[19]陈彦菲.校园内场景的虚拟漫游技术研究[硕士学位论文].大连：大连理工大学结构工程专业,2008.
[20]Jason Gregory. Game Engine Architecture. A K Peters.2009:197-259.
[21]王章野,陆艳青,彭群生.大规模场景的消隐技术.计算机工程与应用,2001,9：8-12.
[22]Christer Ericson. Real-Time Collision Detection. Elsevier.2005.
[23]刘波,王章野,王丽英等.大规模城市场景的高效建模及其实时绘制.计算机辅助设计与图形学学报,2008,20(9)：1153-1162.
[24]周昆,潘志庚,石教英.多细节层次模型间的平滑过渡.计算机辅助设计与图形学学报,2000,12(6)：463-467.
[25]周昆,潘志庚,石教英.基于三角形折叠的网格简化算法.计算机学报,1998,21(6)：506-514.
[26]J Cohen, M Olano, D Manocha. Appearance-preserving simplification. Computer Graphics (SIGGRAPH'98),1998,31:189-198.
[27]Alan Watt, Fabio Policarpo,3D Games Real-time Rendering and Software Technology. Pearson Education,2001.
[28]Lindstrom P and Turk G. Fast and memory efficient Polygonal simplification. IEEE Visualization'98 Conference Proeeedings,1998:279-286.
[29]Garland.M, Heekbert.P. Surface Simplification Using Quadric Error Metrics. Proceedings ofSIGGRAPH'97,1997:209-216.
[30]陈实.基于Web-3D的网络虚拟社区的交互设计.包装工程.2008.29(4)：84-86.
[31]周晓云,何大曾,刘慎权.一种层次模型构造方法.中国图像图形学报,1997,2(8)：556-561.
[32]Frank Luna. Introduction to 3D Game Programming with DirectX 9.0c:a shader approach. Wordware Publishing.2006.
[33]Frank Luna. Introduction to 3D Game Programming with DirectX 9.0. Wordware Publishing.2003.