數(shù)據(jù)可視化技術(shù)及其應(yīng)用分析解析

數(shù)據(jù)可視化技術(shù)及其應(yīng)用摘要:數(shù)據(jù)可視化是計算機學(xué)科的一個重要研究方向。文中簡要介紹了數(shù)據(jù)可視化所需的技術(shù):數(shù)據(jù)預(yù)處理、映射、顯示以及可視化技術(shù)在醫(yī)學(xué)、氣象預(yù)報、工程及數(shù)據(jù)挖掘中的應(yīng)用。關(guān)鍵詞:數(shù)據(jù)可視化;計算機圖形學(xué)DatavisualizationanditsapplicationsAbstract:Datavisualizationisanimportantresearchareaincomputerscience.Inthispaper,datavisualizationtechnologiesincludingdatapre2treatment,mappinganddisplayingarebrieflyintroduced,anditsapplicationsinmedicine,weatherforecasting,engineeringanddataminingarepresentedalso.Keywords:Datavisualization;Computergraphics1引言隨著科學(xué)技術(shù)的不斷發(fā)展,大量的由計算機產(chǎn)生的中間數(shù)據(jù)都需要進行可視化處理,以求達到輔助分析、再現(xiàn)客觀的目的?，F(xiàn)代的數(shù)據(jù)可視化[1]技術(shù)指的是運用計算機圖形學(xué)和圖像處理技術(shù),將數(shù)據(jù)換為圖形或圖像在屏幕上顯示出來,并進行交互處理的理論、方法和技術(shù)。它涉及到計算機圖形學(xué)、圖像處理、計算機輔助設(shè)計、計算機視覺及人機交互技術(shù)等多個領(lǐng)域。換句話說,可視化技術(shù)是一種計算方法。它將符號描述轉(zhuǎn)變成幾何描述,從而使研究者能夠觀察到所期望的仿真和計算結(jié)果。此外可視化技術(shù)提供了將不可見轉(zhuǎn)化為可見的方法。它豐富了科學(xué)發(fā)現(xiàn)的過程,促進對未知事物的領(lǐng)悟。近年來,可視化的應(yīng)用范圍隨著計算機技術(shù)、圖形學(xué)技術(shù)的發(fā)展而不斷拓寬,除了繼續(xù)在傳統(tǒng)的醫(yī)學(xué)、航空學(xué)、汽車設(shè)計、氣象預(yù)報和海洋學(xué)領(lǐng)域的深入研究外,近年來,隨著互聯(lián)網(wǎng)絡(luò)技術(shù)和電子商務(wù)的發(fā)展,信息可視化已經(jīng)成為可視化技術(shù)的熱點研究內(nèi)容。應(yīng)用可視化技術(shù),可以在具有大量高維信息的金融、通信和商業(yè)領(lǐng)域中發(fā)現(xiàn)各自數(shù)據(jù)中所隱含的內(nèi)在規(guī)律,從而為決策提供依據(jù)。事實上,可視化技術(shù)已經(jīng)成為許多領(lǐng)域必不可少的計算機輔助后置數(shù)據(jù)處理部分1IntroductionWiththedevelopmentofscienceandtechnology,computergeneratedlargeamountsofintermediatedataarerequiredforvisualprocessing,inordertoachievethecomputer-aidedanalysis,reproductionoftheobjectivepurpose.Datavisualizationofmodern[1]technologyreferstotheuseofcomputergraphicsandimageprocessingtechnology,thedataintothegraphicsorimagesdisplayedonthescreen,andthetheory,methodandtechnologyofinteractiveprocessing.Itinvolvesmanyfieldsofcomputergraphics,imageprocessing,computeraideddesign,computervisionandhuman-computerinteractiontechnology.Inotherwords,thevisualizationtechnologyisakindofcalculationmethod.Itwillbethesymboldescriptionintoageometricdescription,simulationandcalculationresultssothatresearcherscanobservethedesired.Inaddition,visualizationtechnologyprovidestheinvisibleintothevisiblemethod.Itisrichintheprocessofscientificresearch,promotionoftheunknown.Inrecentyears,thescopeofapplicationofvisualizationofexpandingwiththedevelopmentofcomputertechnology,computergraphicstechnology,besidesthefurtherstudyintraditionalmedicine,aviation,automobiledesign,meteorologicalandoceanographicfield,inrecentyears,withthedevelopmentofInternettechnologyande-commerce,informationvisualizationhasbecomeahotspotofresearchcontentsofvisualizationtechnologythe.Theapplicationofvisualizationtechnology,canfindtheinherentrulesimpliedintheirdatainwhichalargenumberofhighdimensionalinformationoffinancial,communicationsandbusinessfields,soastoprovidethebasisfordecisionmaking.Infact,thevisualizationtechnologyhasbecomeessentialtomanyapplicationsofcomputeraideddatapostprocessingpartofthe2數(shù)據(jù)可視化技術(shù)用于創(chuàng)建和操作的可視化技術(shù)由數(shù)據(jù)集合生成的圖形描述。有些可視化技術(shù)是針對某些特別的應(yīng)用開發(fā)的,而另一些技術(shù)具有普遍的適用性。這一部分主要針對通用的可視化技術(shù)。此外,可視化技術(shù)涵蓋范圍較廣,這里只將可視化技術(shù)按一般可視化所必需的過程劃分為“數(shù)據(jù)預(yù)處理”、“映射”、“繪制”和“顯示”四步。2datavisualizationtechnologyUsedinthevisualizationtechnologytocreateandmanipulatedescribedbythedatasetgeneratedgraph.Somevisualizationtechnologyisdevelopedforsomespecialapplication,andsomeothertechniqueshavegeneralapplicability.Thispartmainlyaimedatthevisualizationtechnologyofgeneral.Inaddition,thevisualizationtechnologycoversawiderange,hereonlythevisualizationtechnologyisnecessaryaccordingtothevisualizationprocessinto"dataprocessing","map","drawing"and"show"thefourstep.2.1數(shù)據(jù)預(yù)處理可視化模塊輸入來自計算機的模擬數(shù)據(jù)和實驗/測量數(shù)據(jù),此外還包括數(shù)據(jù)庫中數(shù)據(jù)的調(diào)用?？梢暬幚淼膶ο蟀ā胺枴?、“結(jié)構(gòu)”、“圖像”與“信號”。原始的符號、結(jié)構(gòu)、圖像與信號等對象的生成與獲取是從事科學(xué)與工程計算和實驗的科學(xué)家或工程師的任務(wù)。如何將這些數(shù)據(jù)變換成可視的圖形(圖像)信息,則是從事科學(xué)計算可視化應(yīng)用的科學(xué)家和工程師的任務(wù)。他們與從事基礎(chǔ)研究或工程研究的科學(xué)家們相結(jié)合,運用可視化工具,實現(xiàn)并完成將不可見的對象變換成可見圖像的過程。通常對這些原始數(shù)據(jù)的處理應(yīng)包括以下兩個方面:(1)原始數(shù)據(jù)預(yù)處理及存儲通常用于可視化的原始數(shù)據(jù)預(yù)處理部分要涉及到以下的操作:1)數(shù)據(jù)格式及其標(biāo)準(zhǔn)化;數(shù)據(jù)變換技術(shù);3)數(shù)據(jù)壓縮和解壓縮。經(jīng)過上述處理的數(shù)據(jù)可能會具有較大的數(shù)據(jù)容量。通常要采用標(biāo)準(zhǔn)化的數(shù)據(jù)交換格式存儲。美國國家超級計算中心的NASA等單位研究提出的科學(xué)數(shù)據(jù)存儲和交換格式/結(jié)構(gòu),如HDF、CDF和NetCDF等。這些數(shù)據(jù)格式通常具有自描述的特性,易于存儲和讀取,被廣泛用于海洋、氣象環(huán)境模式計算以及大規(guī)模數(shù)值計算等方面。(2)面向可視化方法的數(shù)據(jù)處理針對不同的可視化方法和內(nèi)容,需要對原始數(shù)據(jù)做進一步的變換處理,以滿足可視化要求。例如,對于醫(yī)學(xué)圖像的三維重建,就需要對原始CT圖像序列進行三維的濾波、重采樣、三維圖像分割與邊緣檢測等預(yù)處理。對原始數(shù)據(jù)進行變換處理的操作主要包括:1)數(shù)據(jù)規(guī)范化處理;2)濾波處理;3)平滑處理;4)網(wǎng)格重新劃分;5)坐標(biāo)變換;6)幾何變換;7)線性變換;8)分割與邊緣檢測;9)特征檢測、增強和提取;10)查色表操縱和特征映射等等。2.1datapreprocessingThevisualizationmoduleinputsimulationdataandexperimental/fromcomputermeasurementdata,inadditiontothedatainthedatabasecall.Visualprocessingofobjectsincluding"symbol","structure","image"and"signal".Withtheacquisitionoftheoriginalsymbol,structure,imageandsignaloftheobjectisengagedinscientificandengineeringcalculationandexperimentalscientistorengineertask.Howthesedatawillbetransformedintovisualgraphic(image)information,isengagedinthevisualizationapplicationscientistsandengineersthetaskofscience.Theyarecombinedwiththescientistsengagedinbasicresearchorengineering,usingvisualizationtools,implementationandcompletionwillnotvisibleobjectistransformedintoavisibleimageprocess.Commontotheseoriginaldataprocessingshouldincludethefollowingtwoaspects:(1)thedataprocessingandstorageUsuallyusedforthepre-processingoftheoriginaldatapartvisualizationinvolvesthefollowingoperations:1)dataformatanditsstandardization;Datatransformationtechnology;3)datacompressionanddecompression.Aftertheaboveprocessingdatamayhasalargedatacapacity.Usuallyuseastandarddataexchangeformat.ScientificdatastorageUSANationalSupercomputingCenterinNASAunitofandexchangeformat/structure,suchasHDF,CDFandNetCDFetc..Thesedataformatisusuallyhasthecharacteristicsofselfdescription,easytostoreandread,iswidelyusedinmarine,meteorologicalcomputingenvironmentmodelandlarge-scalenumericalcalculations.(2)forthevisualizationofdataprocessingThevisualizationmethodsandcontentofdifferent,needtotransformafurthertreatmentoftheoriginaldata,tomeetthevisualrequirements.Forexample,forthe3Dreconstructionofmedicalimage,need,resampling,3Dimagesegmentationandedgedetectionpreprocessingof3DfilteringoftheoriginalCTimagesequence.Transformtheoperationoftheoriginaldatamainlyincludes:1)standardizeddataprocessing;2)filtering;smoothing;3)4)5)remeshing;coordinatetransformation;geometrictransformation;6)7)lineartransform;8)segmentationandedgedetection;9)featuredetection,enhancementandextraction;10)colorlook-uptablemanipulationandfeaturemappingetc..2.2映射映射模塊是完成將數(shù)值數(shù)據(jù)轉(zhuǎn)變成幾何數(shù)據(jù)的功能,因此映射功能實質(zhì)上完成的是數(shù)據(jù)建模功能,是可視化技術(shù)的核心?？梢暬幚淼臄?shù)據(jù)類型隨著應(yīng)用領(lǐng)域的不同而不同,因此對不同類型的應(yīng)用數(shù)據(jù)應(yīng)采用不同的映射技術(shù)。一些常見的方法如:應(yīng)用圖形中可識別的變量來驗證維數(shù)的基數(shù)。(2)使用縮放比例和偏移量匹配數(shù)值范圍。(3)使用衍生值(殘差、logs)來強調(diào)變化。(4)使用投影來壓縮信息、獲得統(tǒng)計量。(5)使用隨機抖動來區(qū)分重疊。(6)使用多視圖來處理隱藏關(guān)系高維信息。(7)使用有效的網(wǎng)格關(guān)鍵字或標(biāo)簽來幫助理解2.2mappingMappingmoduleistocompletethenumericaldataintogeometricdata,sothemappingfunctionisessentiallycompletedatamodelingcapabilities,isthecoreofvisualizationtechnology.Visualizationofdatatypeswiththeapplicationisdifferent,sotheapplicationdataofdifferenttypesshouldadoptdifferentmappingtechnique.Somecommonmethodssuchas:Variablescanbeidentifiedusinggraphicstovalidatethedimensionofthebase.(2)thematchingnumericalrangeusingthescalingandoffset.(3)usingthederivedvalue(residual,logs)toemphasizethechanges.(4)usingtheprojectiontocompressinformation,toobtainstatistics.(5)usingrandomjittertodistinguishoverlapping.(6)theuseofmultiviewtodealwithhighdimensionalinformationhiddenrelationships.(7)theuseofeffectivemeshkeywordsortagstohelpunderstand2.3繪制繪制功能應(yīng)完成將幾何數(shù)據(jù)轉(zhuǎn)換成圖像的過程,計算機圖形學(xué)中真實感成像包括兩部分:物體的精確圖形表示;場景中光照效果的適當(dāng)物理描述。物體的精確圖形表示包括幾何體建模技術(shù)、掃描轉(zhuǎn)換技術(shù)、反走樣技術(shù)、隱藏面消除技術(shù)。一個完整精確的圖形描述通常需要綜合應(yīng)用這些技術(shù),同時,還要考慮用戶對圖形表示的需要,不能把圖形模型建得過于簡單,也不能過于復(fù)雜。光照效果包括光的反射、透明性、表面紋理和陰影。光照效果由描述物體表面各點光強的光照模型來表示,為可見物體建立光照效果模型是一個非常復(fù)雜的過程。大多數(shù)軟件都采用由物體表面光強度的物理公式推導(dǎo)出來的簡化光照模型。2.3drawingDrawingfunctionshouldcompletethegeometricdataintoimageprocess,computergraphics,realisticimageincludestwoparts:saidaccurategraphicobject;describetheappropriatephysicallighteffectsofthescene.Precisiongraphicsobjectrepresentationsincludinggeometrymodelingtechnology,scanconversion,antialiasing,hiddensurfaceremovaltechnology.Acompleteandaccuratedescriptionofthegraphicsusuallyrequirestheintegratedapplicationofthesetechniques,atthesametime,butalsoconsidertheneedsofuserstographically,notthegraphicsmodelistoosimple,cannotbetoocomplex.Thelighteffectincludingthereflectionoflight,transparency,surfacetextureandshading.Thelighteffectbydescribinganobjectpointsonthesurfaceofthelightintensityofilluminationmodeltorepresent,establishedasavisibleobjectilluminationmodelisaverycomplexprocess.Mostsoftwareusedbytheopticalsurfacestrengthofthesimplifiedformuladerivedphysicalilluminationmodel.2.4顯示顯示模塊的功能是將繪制模塊生成的圖像數(shù)據(jù),按用戶指定的要求進行輸出。顯示模塊類似于圖形用戶界面(GUI)技術(shù),其對應(yīng)的軟件層提供各種設(shè)備的驅(qū)動程序。顯示模塊除了完成圖像信息輸出功能外,用戶的反饋信息也是通過顯示模塊傳送到其它軟件層中,以實現(xiàn)人機交互。人機交互是可視化的一項重要指標(biāo),許多可視化要求實現(xiàn)動態(tài)調(diào)整映射關(guān)系,通過改變視圖遍歷數(shù)據(jù),視圖縮放等操作。2.4displayThedisplaymoduleisthefunctionofimagedatawillberenderingmodule,outputaccordingtouserspecifiedrequirements.Thedisplaymoduleissimilartothegraphicaluserinterface(GUI)technology,thecorrespondingsoftwarelayerprovidesallkindsofdriverequipment.Displaymoduleinadditiontocompletingtheimageinformationoutputfunction,theuserfeedbackinformationisthroughthedisplaymoduletotheothersoftwarelayer,inordertoachievehuman-computerinteraction.Humancomputerinteractionisanimportantindexforvisualization,dynamicadjustmentmappingrequiresalotofvisualization,bychangingtheviewthroughadata,viewzoom.Thederivedformulassimplifiedilluminationmodel.3數(shù)據(jù)可視化的應(yīng)用3.1醫(yī)學(xué)可視化技術(shù)已廣泛應(yīng)用于診斷醫(yī)學(xué)、整形與假肢外科中的手術(shù)規(guī)劃與輻射治療規(guī)劃等方面。在以上應(yīng)用中核心技術(shù)是將過去看不見的人體器官能以二維圖像形式顯示出來或重建它們的三維模型。由于三維醫(yī)學(xué)圖像構(gòu)模涉及的數(shù)據(jù)量大、體元構(gòu)造算法復(fù)雜、運算量大,因此至今仍是醫(yī)學(xué)圖像可視化技術(shù)中的瓶頸所在。在這一領(lǐng)域中圖像處理技術(shù)占主流,而計算機視覺與圖形學(xué)則在整形外科的手術(shù)中起主要作用。圖1為腦部核磁共振圖像序列重構(gòu)的三維腦部圖像。此類三維圖像將有助于醫(yī)生決定是否需要外科手術(shù),應(yīng)用何種方法和需要何種硬件工具的問題。目前在醫(yī)學(xué)可視化領(lǐng)域主要包含三方面的研究熱點:圖像分割技術(shù)、實時渲染技術(shù)和多重數(shù)據(jù)集合的圖像標(biāo)定技術(shù)。這些技術(shù)的發(fā)展將進一步促進可視化技術(shù)在醫(yī)學(xué)技術(shù)中的推廣。3.2氣象預(yù)報氣象預(yù)報中涉及到大量的可視化內(nèi)容,從普通的云圖到中尺度數(shù)值預(yù)報。大量的氣象觀測數(shù)據(jù)都必須經(jīng)過可視化后再向用戶提供信息。一方面,可視化可將大量的數(shù)據(jù)轉(zhuǎn)換為圖像,在屏幕上顯示出某一時刻的等壓面、等溫面、漩渦、云層的位置及運動、暴雨區(qū)的位置及其強度、風(fēng)力的大小及方向等,使預(yù)報人員能對未來的天氣作出準(zhǔn)確的分析和預(yù)測。另一方面,根據(jù)全球的氣象監(jiān)測數(shù)據(jù)和計算結(jié)果,可將不同時期全球的氣溫分布、氣壓分布、雨量分布及風(fēng)力風(fēng)向等以圖像形式表示出來,從而對全球的氣象情況及其變化趨勢進行研究和預(yù)測。圖2為三維空間里的風(fēng)暴前鋒模型。圖中描述了冷暖鋒面及鋒面相交時的壓力場分布。Applicationof3datavisualizationThe3.1medicineOperationplanningandradiationtreatmentplanning,visualizationtechnologyhasbeenwidelyusedinmedicaldiagnosis,plasticandartificiallimbsurgery.Thecoretechnologyintheaboveapplicationsistheinvisiblehumanorganstotwo-dimensionalimageordisplayof3Dmodelsandtheir.The3Dmedicalimagemodelinginvolvesalargeamountofdata,bodystructurecomplexity,largeamountofcomputation,soitisstillmedicalimagevisualizationtechnologybottleneck.Inthefieldofimageprocessingtechnologyinthemainstream,andcomputervisionandgraphicsintheorthopaedicoperationplaysamajorrolein.Figure1isathree-dimensionalimagesofthebrainmagneticresonanceimagesequencereconstruction.Thethree-dimensionalimagewillhelpdoctorsdecidewhethertoneedsurgicaloperation,andwhatmethodsandproblemsneedwhatkindofhardwaretools.Atpresentinthemedicalresearchfocusmainlyincludesthreeaspects:imagesegmentationimagetechnology,real-timerenderingtechnologyandmultipledatasetsofcalibrationtechnology.Thedevelopmentofthesetechnologieswillfurtherpromotethevisualizationtechnologyinmedicaltechnology.3.2weatherforecastRelatedtothevisualcontentofalotofweatherforecast,fromordinaryimagestomesoscalenumericalweatherprediction.Meteorologicalobservationdatamustbeapprovedbythevisualizationtoprovideinformationtotheuser.Ontheonehand,visualizationcanbealotofdataintoimage,showingthepositionofisobariconetime,isothermalsurface,vortex,cloudsandmotion,rainfallareaandintensity,thesizeofthewindandthedirectiononthescreen,theforecastertomakeanalysisandpredictionoffutureweather.Ontheotherhand,accordingtotheglobalweathermonitoringdataandcalculationresults,thedifferentperiodsofglobaltemperaturedistribution,pressuredistribution,distributionofrainfallandthedirectionofthewindintheformofimagerepresentation,researchandforecasttheglobalweathersituationandtrend.Figure2isthestormstrikermodelinthree-dimensionalspace.Figuredescribesthecoldfrontandthefrontintersectionwhenthepressurefielddistribution.3.3工程可視化在工程中有著廣泛的應(yīng)用,這里僅就其在計算流體力學(xué)中的應(yīng)用為例進行說明。計算流體力學(xué)(CFD)就是求解流體偏微分方程,即Navier2Stokes方程的數(shù)值解,這些方程式是航空學(xué)、汽車設(shè)計、氣象預(yù)報和海洋學(xué)等應(yīng)用研究的核心,也是理解流體動力學(xué)的基礎(chǔ)。計算流體力學(xué)領(lǐng)域的主要研究方向可分為科學(xué)計算(求解算法)與可視化(描述復(fù)雜矢量場技術(shù))兩部分,其主要目的是對流體運動的仿真。隨著超級計算機的應(yīng)用,計算流體力學(xué)仿真的精度和復(fù)雜性提高很快,例如目前已可對復(fù)雜幾何形狀的三維Navier2Stokes流進行仿真。在流場計算的一般過程中,可視化技術(shù)起著十分重要的作用。首先,可視化技術(shù)提供交互設(shè)計手段以方便與加快物體的定義過程,研究人員可直觀地校驗物體各部分的幾何尺寸大小、部件間是否留有縫隙、物體表面是否光滑等。其次,在對計算區(qū)域進行網(wǎng)格剖分時,可視化技術(shù)能把生成的網(wǎng)格顯示出來,以便讓研究人員檢驗并及時調(diào)整和伸縮網(wǎng)格線,使之形成合理的空間分布。最后,在計算和對計算結(jié)果的分析過程中,可視化技術(shù)的作用更大。它利用計算機圖形學(xué)所提供的各種方法描述流場中的各種物理量的分布情況,如壓力、密度等標(biāo)量和速度等矢量(如圖3所示),并用不同顏色的等值線(面)或不同深淺的同種顏色填充網(wǎng)格來表示標(biāo)量的數(shù)值差別,以帶箭頭的線段來描繪矢量的方向,對沖擊波、渦流、駐點等各種流場結(jié)構(gòu),也可用計算機圖形學(xué)提供的方法進行描繪。而且,可視化技術(shù)實時交互地變化畫面大小并提供動態(tài)顯示,以使分析者看清流場中各種現(xiàn)象的細節(jié)并作進一步分析。3.3EngineeringVisualizationiswidelyusedinengineering,hereonlyforitsapplicationincomputationalfluiddynamicsasanexample.Computationalfluiddynamics(CFD)isthesolutionoffluidpartialdifferentialequation,namelythenumericalsolutionsoftheNavier2Stokesequation,theequationisthecoreapplicationofAeronautics,automotivedesign,meteorologicalandoceanography,butalsothebasisfortheunderstandingoffluiddynamics.Themainresearchdirectionofthefieldofcomputationalfluiddynamicscanbecalculatedintoscientific(algorithm)andvisual(describethecomplexvectorfield)thetwopart,itisthemainpurposeofthefluidMotionsimulation.Withtheapplicationofsupercomputer,precisionandcomplexityofcomputationalfluiddynamicssimulationtoimprovesoon,forexample,hasthecomplexThreedimensionalgeometryofNavier2Stokesflowsimulation.Thegeneralprocessflowcalculation,visualizationtechniquesplayaveryimportantrole.Firstofall,thevisualizationtechnologytoprovideinteractivedesignmeanstofacilitateandacceleratetheprocessofobjectdefinition,researcherscanintuitivelythecheckthegeometrysize,whetherthereisagapbetweenparts,theobjectsurfaceissmooth.Secondly,intheregionisdividedintogrid,visualizationtechnologycanmakethemeshgenerationanddisplay,inordertoallowresearcherstotestandadjustandtelescopicgridlines,toformareasonabledistributionofspace.Finally,inthecourseofcalculationandAnalysisonthecalculationresults,thevisualizationtechnologyhasmoreinfluenceon.ItusesavarietyofmethodsofcomputergraphicsprovidesadescriptionofvariousphysicalquantitiesintheflowfieldofCloth,suchaspressure,densityandvelocityscalarvector(asshowninFigure3),andthecontoursofdifferentcolors(surface)orvaryingshadesofthesamecolorfillingmeshtor