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it Interactive Exploration of Large 3-D Unstructured-Grid Data

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NASAContractorReport201618

ICASEReportNo.96-63it󰀀•/

ICA

INTERACTIVEEXPLORATIONOFLARGE

3-DUNSTRUCTURED-GRIDDATA

Kwan-LiuMa

ScottLeutenegger

DimitriMavriplis

NASAContractNo.NAS1-19480October1996

InstituteforComputerApplicationsinScienceandEngineeringNASALangleyResearchCenterHampton,VA23681-0001

OperatedbyUniversitiesSpaceResearchAssociation

NationalAeronauticsandSpaceAdministration

LangleyResearchCenterHampton,Virginia

23681-0001InteractiveExplorationof

Large3-DUnstructured-GridData

Kwan-LiuMat

InstituteforComputerApplicationsinScienceandEngineering

ScottLeuteneggertMathematicsandComputerScienceDepartmentUniversityofDenver

DimitriMavriplistInstituteforComputerApplicationsinScienceandEngineering

Abstract

Visualizingunstructured-griddatafromaerodynamicscalculationsischallengingbecauseoftheassociatedmeshesaretypicallylargeinsizeandirregularinbothshapeandresolu-tion.Thisresearchinvestigatesappropriatedatastructuresandrenderingmethodstoallowinteractiveexplorationofthedata.Inconjunctionwithfastsplattingrendering,amultiresolutiondatarepresentationbasedonagglomerationisusedtomakepossibleinteractivevisualizationonaworkstation.Thatis,dataarerenderedataparticularresolutionaccordingtovisualizationparamentersaswellasthespeedandmemorycapacityoftheworkstation.Interactivevisualizationallowstheusertoquicklydetermineregionsofinterestandimportantvisualizationparameterssuchasviewingdirectionandtransferfunctions.Wethenapplyamoreaccurate,expensiverenderingmethodtotheorignaldataontheregionsofinterest.Theoriginaldataarestoredondisk.WeshowwithbothanalysisandexperimentalresultsthatR-treeisabetterdatastructureforfastretrievalofsuchdisk-residentdata.

tThisresearchwassupportedbytheNationalAeronauticsandSpace'AdministrationunderNASAcon-tractNAS1-19480whiletheauthorwasinresidenceattheInstituteforComputerApplicationsinScienceandEngineering(ICASE)_NASALangleyResearchCenter,Hampton,

VA23681-0001.1Introduction

Inaerodynamicscalculations,unstructuredgridsareusedtomodelobjectswithcomplex

geometry.Becausethegridsaretypicallylargeinsizeandirregularinshapeandresolu-

tion,oftenspecialdataprocessingandrenderingalgorithmsareneededtomakepossiblevisualizationofthesimulationresults.Thisresearchstudiestheneededsoftwaresupport

forconductingthedesirableiterative,near-interactivevisualizationprocesstoanalyzevery

largeunstructured-griddataonanaverageworkstation.TheproposedvisualizationprocessincludesmainlytwostepsasshowninFigure1.The

firststepattemptstoderivedesirableviewingandrenderingparametersandtolocatere-gionsofinterest,asub-volume.Thismaybeperformedonaworkstationusingafastbut

lessaccuraterenderingalgorithmonacoarserepresentation,thusamuchsmallerversion,

oftheoriginaldatastoredinthemainmemoryoftheworkstation.Consequently,weneed

amulti-resolutionrepresentationoftheoriginaldata(mrrd).Themrrdallowsinteractive

explorationofthedata.Onceahotspotisidentifiedataparticularresolution,theuser

mayswitchtoviewingatahigher-resolutionforfurtherexploration.Thisexplorationpro-cesscontinuesuntiltheregionofinterestandviewingaswellasrenderingparametersare

completelydetermined.Weuseafast,approximatedsplattingalgorithmforrenderingdata

atresolutionsaccordingtovisualizationrequirements,aswellasthespeedandmemory

capacityoftheworkstation.Thesecondsteptakestheparametersderived,extractstheselectedsub-volumeoutofthe

originaldata,andinvokesamoreaccuraterenderingprogramtoproducehighqualityvisu-alizationresults.Thisstepmaybeperformedoneitheraworkstationorahigh-performance

computer.Thesub-volumerepresentsaspatialregionofinterestusuallymuchsmallerthan

theoverallgriddomainandthusmayberenderedmoreefficientlyonaworkstation.Notethatbecauseofitssize,theoriginaldatasetmustbestoredondisk.Itisthenessentialto

haveadequatedatabasesupportsuchthatasub-volumecanbequicklyretrievedfromdisk.Therefore,werepresentthedataasanR-tree[13],anefficienthierarchicaldatastructure

thathasbeenwidelyadoptedbymanydatabaseapplications.

Dataexplorationisinherentlyiterative.Thevisualizationprocessandsystemarchitec-

turedevelopedinthisresearchallowcomputationalscientiststostudytheirdataatthe

highestpossibleresolutioninamoreefficientmanner,ratherthanreducingthedataorop-

eratingataveryinefficientbatch-mode.Inthispaper,wedescribetheconstructionofthe

rnrrd,demonstratetheeffectivenessofthefastsplattingrenderingmethod,andshowthatR-treesworkbetterthanoctreeswhichhavebeenwidelyusedbythevisualizationcommunity.

Testresultswereobtainedbyusingafour-milliontetrahedra-celldataseton

workstations.Fastdataexplorationatmultipleresolutionstodetermineregionsofinterest,renderingandviewingparameters.

)

Figure1:Theproposedvisualizationprocessandsystemarchitecture.

2Multi-resolutionRendering

Multiresolutiondatavisualizationhasbeenanactiveareaofresearchbutmostprevious

合集下载

FLAC3D学习

FLAC3D学习

FLAC3D学习

1.FLAC3D的基本知识介绍

岩土工程结构的数值解是建立在满足基本方程（平衡方程、几何方程、本构方程）和边界条件下推导的。由于基本方程和边界条件多以微分方程的形式出现，因此，将基本方程近假发改用差分方程（代数方程）表示，把求解微分方程的问题改换成求解代数方程的问题，这就是所谓的差分法。差分法由来已久，但差分法需要求解高阶代数方程组，只有在计算机的出现，才使该法得以实施和发展。FLAC3D（FatLagrangianAnalyiofContinua）由美国Itaca公司开发的。目前，FLAC有二维和三维计算程序两个版本，二维计算程序V3.0以前的为DOS版本，V2.5版本仅仅能够使用计算机的基本内存（64K），所以，程序求解的最大结点数仅限于2000个以内。1995年，FLAC2D已升级为V3.3的版本，其程序能够使用护展内存。因此，大大发护展了计算规模。FLAC3D是一个三维有限差分程序，目前已发展到V2。1版本。

FLAC3D的输入和一般的数值分析程序不同，它可以用交互的方式，从键盘输入各种命令，也可以写成命令（集）文件，类似于批处理，由文件来驱动。因此，采用FLAC程序进行计算，必须了解各种命令关键词的功能，然后，按照计算顺序，将命令按先后，依次排列，形成可以完成一定计算任务的命令文件。

FLAC3D是二维的有限差分程序FLAC2D的护展，能够进行土质、岩石和其它材料的三维结构受力特性模拟和塑性流动分析。调整三维网格中的多面体单元来拟合实际的结构。单元材料可采用线性或非线性本构模型，在外力作用下，当材料发生屈服流动后，网格能够相应发变形和移动（大变形模式）。FLAC3D采用的显式拉格朗日算法和混合-离散分区技术能够非常准确发模拟材料的塑性破坏和流动。由于无须形成刚度矩阵，因此，基于较小内存空间就能够求解大范围的三维问题。FLAC3D采用ANSIC++语言编写的。

1对模拟塑性破坏和塑性流动采用的是“混合离散法”。这种方法比有限元法中通常采用的“离散集成法”更为准确、合理。

专业英语-IT专业英语词汇精选（U）

专业英语-IT专业英语词汇精选（U）

其它-专业英语-IT专业英语词汇精选(U) U unit 装置；部件；单元 U update 更新

U user 用户 U you 你〖网语〗

U.N.S.C. United Nations Statistical Commission 联合国统计委员会

U.N.S.O. United Nations Statistical Office 联合国统计局 U / L Up – Link 上行链路

ua Ukrainian SSR 乌克兰（域名） UA Ultima Ascension 《创世纪9：升天》〖游戏名〗

UA Ultrasonic Attenuation 超声波衰减

UA Uniform Array 一致阵列 UA Unit Address 单元地址

UA Universal Agent 全权代理人 UA Unnumbered Acknowledgment 未编号确认

UA User Agent 用户代理（程序）

UA User Area 用户区 UAA Universal Access Authority 通用访问权，通用存取授权

UAAS Universal Accounting Automatic System 通用自动记账系统 UAC Uninterrupted Automatic Control 不间断性自动控制

UACN Universal Automated Communication Network 万国自动通信网络

UAD Uniform Automatic Processing System 统一的自动处理系统 UADS User Attribute Data Set 用户属性数据集

UADSL Universal Asymmetric Digital Subscriber Line 通用非对称数字用户线

UAF User Authorization File 用户授权文件，用户认可文件 UAG Universal Address Group 通用地址组

IDM数据模型

IDM数据模型

iDM:AUnifiedandVersatileDataModelforPersonal

DataspaceManagement∗

Jens-PeterDittrichMarcosAntonioVazSalles

ETHZurich

8092Zurich,Switzerland

dbis.ethz.ch|

ABSTRACT

PersonalInformationManagementSystemsrequirea

powerfuland

versatiledatamodelthatisabletorepresentahighlyheterogeneousmixofdatasuchasrelationaldata,XML,filecontent,folderhier-

archies,emailsandemailattachments,datastreams,RSSfeedsand

dynamicallycomputeddocuments,e.g.ActiveXML[3].Interest-

ingly,untilnownoapproachwasproposedthatisabletorepresent

alloftheabovedatainasingle,powerfulyetsimpledatamodel.

Thispaperfillsthisgap.WepresenttheiMeMexDataModel(iDM)

forpersonalinformationmanagement.iDMisabletorepresent

unstructured,semi-structuredandstructureddatainsideasingle

model.Moreover,iDMispowerfulenoughtorepresentgraph-

structureddata,intensionaldataaswellasinfinitedatastreams.

Icepak-sheet

Icepak-sheet

IcepakÁ¡ªO¤¸¥ó¦bIC«Ê¸Ë¤Wªº·sÀ³¥Î

Icepak's Thin Conducting Plate Technology Provides New Options for IC

Package Thermal Modeling

By Dr. Kamal Karimanal, Customer Support Engineer

Icepak Team, Fluent Inc.

The Magic of Thin Conducting Plates

The use of a "zero thickness" planar object for avoiding small cell volumes is no new trick to

users of finite volume-based thermal analysis software. Contact resistance plates are often

used for modeling temperature jump due to 1-D heat flow across an imperfect contact.

Similarly, you can use thin conducting plates as zero thickness geometry objects to model

interfaces where 3-D conduction cannot be ignored. Copper planes in PCB and IC packages

are a good example. The thin conducting plate model in Icepak solves the full 3-D conduction

equation using finite volume cells that do not extend outside the plane, which eliminates undesirable grid bleeding in the fluid regions.