基于Creator的三维场景模型优化技术研究
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摘要
虚拟现实技术的主要目标之一是允许用户以尽可能自然的方式与虚拟世界进行交互,虚拟现实系统中的虚拟物体给人真实存在的感觉。就计算机图像来说,以目前的计算机图形学的水平,只要有足够的计算时间,就可以生成精确细致的画面。但VR系统的要求是实时显示,这不仅仅要求考虑场景效果,还要考虑系统的反应速度。因此,在VR高质量图形的实时生成要求下,如何从软件着手,减少图形画面的复杂度,同时保证三维场景的精确性,已成为虚拟现实中场景生成的主要目标之一。
基于Creator的三维场景优化技术的研究意义在于为解决图形显示质量与显示速度之间的矛盾提供了一条可行而且有效的途径。
本文结合华中师范大学数字校园视景管理系统,以数字校园的三维模型数据库为实例,探讨了在专业三维建模软件MAYA和Creator下构建及优化三维数字校园模型库的方法。主要的研究内容如下:
首先,将现有的实用三维模型优化技术按照OpenFlight模型数据库所包含的三种基本信息进行整理和分类:基于模型几何特征优化,有删除法和合并区域法;基于模型外观属性(节点属性)中纹理的优化,有纹理尺寸和格式的选择,以及公告牌技术等纹理技巧的使用;基于节点数据组织优化(模型层次化结构),有合理组织节点数据、LOD技术、实例技术、外部引用技术的使用。
其次,在前人研究成果的基础之上,并结合在整个系统制作中的经验,总结模型库结构优化的六项策略。
再者,在前人研究成果的基础之上,并结合在整个系统制作中的经验,对离散LOD模型数据制作的原则提出了自己的见解。
最后,结合实例,按照以上的分类对三维模型数据库进行优化,对得到的优化模型与原模型在文件数据量、加载时间、内存占用量等参数进行比较分析,得出采用的模型优化方法在实时系统的可行性和必要性。
The one of aims of Virtual Reality technology is that the user could interact with the virtual world in a natural way as much as possible. The objects in Virtual Reality system give user the felling that they are real. In the current level of computer graphics, it's not a difficult to generate accurate and detailed computer images so far as there is sufficient computing time. However, if you want VR systems are real-time display, there are not only the effect of the scene should be considered, but also the speed of system response. Therefore, in order to ensure the high-quality graphics in VR display real-time, how to reduce the complexity of the graphics screen in the way of software, at the same time guarantee the accuracy of 3D scenes have been one of the main objectives of concreting a VR scene.
The significance of optimizing techniques for the 3D scene model based on Creator is to provide an effective and efficient way to solve the contradiction between the quality and the speed of graphical display.
This paper discusses methods of creation and optimization based on the software which is used to create 3D model such as MAYA and Creator taking the Huazhong Normal University Scene Simulation Management System and the Digital Campus 3D scene model for example. The main content is as follows:
Firstly, optimizing techniques for the 3D scene model are classified into three types according to the basic information in OpenFlight model database. Remove and combine belong to optimizing techniques based on the characteristics of the model geometry. Optimizing techniques based on model attributes are focus on the optimizing of texture. Appropriate size and format as well as some texture techniques such as billboard help debase the EMS memory. Besides, appropriately organizing nodes, and LOD, Instance, External nodes are used to effective optimize the hierarchy structure of the database.
Moreover, this paper sums up six strategies on how to optimize model data library referencing the results of previous studies and the experience gained during the work.
Furthermore, this paper puts out some principles about how to product Discrete LOD model data referencing the results of previous studies and the experience gained during the work.
Finally, this paper optimizes the model data according to the classification taking the Huazhong Normal University Digital Campus 3D scene model for example, then compares with the original system in the document, the load time, the EMS memory and so on. A conclusion is draw that these optimizing techniques adopted are feasible and necessary for real-time systems.
基于Creator的三维场景优化技术的研究意义在于为解决图形显示质量与显示速度之间的矛盾提供了一条可行而且有效的途径。
本文结合华中师范大学数字校园视景管理系统,以数字校园的三维模型数据库为实例,探讨了在专业三维建模软件MAYA和Creator下构建及优化三维数字校园模型库的方法。主要的研究内容如下:
首先,将现有的实用三维模型优化技术按照OpenFlight模型数据库所包含的三种基本信息进行整理和分类:基于模型几何特征优化,有删除法和合并区域法;基于模型外观属性(节点属性)中纹理的优化,有纹理尺寸和格式的选择,以及公告牌技术等纹理技巧的使用;基于节点数据组织优化(模型层次化结构),有合理组织节点数据、LOD技术、实例技术、外部引用技术的使用。
其次,在前人研究成果的基础之上,并结合在整个系统制作中的经验,总结模型库结构优化的六项策略。
再者,在前人研究成果的基础之上,并结合在整个系统制作中的经验,对离散LOD模型数据制作的原则提出了自己的见解。
最后,结合实例,按照以上的分类对三维模型数据库进行优化,对得到的优化模型与原模型在文件数据量、加载时间、内存占用量等参数进行比较分析,得出采用的模型优化方法在实时系统的可行性和必要性。
The one of aims of Virtual Reality technology is that the user could interact with the virtual world in a natural way as much as possible. The objects in Virtual Reality system give user the felling that they are real. In the current level of computer graphics, it's not a difficult to generate accurate and detailed computer images so far as there is sufficient computing time. However, if you want VR systems are real-time display, there are not only the effect of the scene should be considered, but also the speed of system response. Therefore, in order to ensure the high-quality graphics in VR display real-time, how to reduce the complexity of the graphics screen in the way of software, at the same time guarantee the accuracy of 3D scenes have been one of the main objectives of concreting a VR scene.
The significance of optimizing techniques for the 3D scene model based on Creator is to provide an effective and efficient way to solve the contradiction between the quality and the speed of graphical display.
This paper discusses methods of creation and optimization based on the software which is used to create 3D model such as MAYA and Creator taking the Huazhong Normal University Scene Simulation Management System and the Digital Campus 3D scene model for example. The main content is as follows:
Firstly, optimizing techniques for the 3D scene model are classified into three types according to the basic information in OpenFlight model database. Remove and combine belong to optimizing techniques based on the characteristics of the model geometry. Optimizing techniques based on model attributes are focus on the optimizing of texture. Appropriate size and format as well as some texture techniques such as billboard help debase the EMS memory. Besides, appropriately organizing nodes, and LOD, Instance, External nodes are used to effective optimize the hierarchy structure of the database.
Moreover, this paper sums up six strategies on how to optimize model data library referencing the results of previous studies and the experience gained during the work.
Furthermore, this paper puts out some principles about how to product Discrete LOD model data referencing the results of previous studies and the experience gained during the work.
Finally, this paper optimizes the model data according to the classification taking the Huazhong Normal University Digital Campus 3D scene model for example, then compares with the original system in the document, the load time, the EMS memory and so on. A conclusion is draw that these optimizing techniques adopted are feasible and necessary for real-time systems.
引文
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[2]何水燕.虚拟校园的碰撞简则研究[D].武汉:华中师范大学计算机应用技术,2006.
[3]M.C.Mike.Optimized Geometry Compression for Real-time rendering[C].In Proc.of the Conference on Visualization'97,October,1997:347-354
[4]普建涛,查红彬.大规模复杂场景的可见性问题研究[J].计算机研究与发展,2005,42(2):236-246
[5]杨宗元.多细节层次模型的研究及应用[D].哈尔滨:哈尔滨工程大学自动化学院,2007.
[6]马小虎.虚拟现实中多细节层次模型的研究[D].浙江:浙江大学CAD&CG国家重点实验室,1996.
[7]唐泽圣.三维复杂模型的实时动态显示[N].北京:计算机世界报,1997,3(31).
[8]史琼芳,汪繁荣.结合3DS Max和Multigen Creator进行三维城市建模的研究[J].北京测绘,2007,(2):16-18.
[9]张曦,王国权,龚国庆.基于Multigen Creator场景模型的建立[J].北京机械工业学院学报,2006,21(2):21-25.
[10]陈永华,王德成,陈燕.基于Creator的三维场景优化技术的应用[J].微计算机信息,2007(8):297-299.
[11]王卫辰,朱真才.虚拟选煤厂三维模型系统的实时性优化[J].计算机仿真,2007,24(9):232-236.
[12]费广正.三维复杂模型快速简化及交互方法的研究[D].北京:中国科学院软件研究所,2001.
[13]Jonathan Shade,Dani Lischinski,David H.Salesin.etc.Hierarchical Image Caching for Accelerated Walkthroughs of Complex Environments[C].Proceedings of the 23rd annual conference on Computer graphics and interactive techniques,August 1996:75-82
[14]Clark J H.Hierarchical geometric models for visible surface algorithms[C],Communications.of the ACM,1976,19:547-55
[15]Rubin S M.The representation and display of scenes with a wide range of detail[J]. The Graphics and Image Processing,1982,19:291-299.
[16]Michael J.DeHaemer,Jr.and Michael J.Zydao Simplification of Objects Rendered by Polygonal Approximations[J].Computer & Graphic.1991,15(2):175-184
[17]Greg Turk.Re-tiling Polygonal surfaces[J].Computer Graphics.1992,26(2):55-64
[18]William J.Schroeder,Jonathan A.Zarge,William E.Lorensen.Decimation of Triangle Meshes[J].Computer Graphics.1992,26(2):65-70
[19]Hoppe,Hugues,Tony DeRose,Tom Duchamp,et.al.Mesh Optimization[J].Computer Graphics(SIGGRAPH Proceedings),1992,27:19-26
[20]Bernd Hamann.A data reduction scheme for triangulated surfaces[J].Computer Aided Geometric Design.1994,11(2):197-214
[21]H.Hoppe.Progress Meshes[C].In proceedings of SIGGRAPH‘96,1996:99-108
[22]陈准,姚国清,梁凤林.基于点删除的TIN简化算法改进[J].国土资源遥感,2005,3:23-26.
[23]王海滨.真实感虚拟场景实时生成技术研究[D].北京:北京交通大学,2000.
[24]张立朝,陈引川,余琳琳.改进的边折叠三角网简化优化算法研究[J].测绘科学,2006,31(6):53-55.
[25]李传良,苏洲.基于面片收缩操作的模型简化算法[J].河海大学常州分校学报,2007,21(3):33-35.
[26]Tomes Akenine-Moller,Eric Haines.Real-Time Rendering(Second Edition)[M].AK Peters,Ltd.2002.
[27]孙策.基于点表示的三维几何模型简化技术[D].辽宁:辽宁工程技术大学,计算机应用,2003.
[28]朱春.三维几何模型的简化算法研究[D].湖南:国防科学技术大学研究生院,2006.
[29]Dieter Schmalstieg,Michael Gervautz.Demand-Driven Geometry Transmission for Distributed Virtual Environments[J].Computer Graphics Forum.1996,15(3):422-432.
[30]王乘,周均清,李利军.Creator可视化仿真建模技术(第1版)[M].武汉:华中科技大学出版社,2005.4.
[31]http://www.eratonce.com/wy/DHFZ2.asp
[32]易国真.城市仿真三维场景库建造的关键技术研究[D].福建:集美大学.2004(5).
[33]孟晓梅,刘文庆.Multigen Creator教程(第1版)[M].北京:国防工业出版社,2005.7.
[34]http://baike.baidu.com/view/1343632.htm.
[35]http://www.lsdn.org/69539/.
[36]胡海鹤.三维网格模型简化技术研究[D].河南:河南科技大学计算机应用技术,2007.
[37]董方敏,张蕊,刘勇等.网格模型简化算法综述[J].三峡大学学报(自然科学版),2007,29(1):54-58.
[38]付鑫.三维网格模型简化算法研究[D].重庆:西南大学计算机信息与科学学院,2008.
[39]周昆,潘志庚,石教英.一种新的基于顶点聚类的网格简化算法[J].自动化学报,1999,25(1):1-8.
[40]Hugues Hoppe,Tony DeRose,Tom Duchamp,John McDonald,Werner Stuetzle.Mesh optimization[C].International Conference on Computer Graphics and Interactive Techniques.1993:19-26.
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