VTK大数据集操作

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1、HowtohandlelargedatasetsinVTKOneofthechallengesinVTKistoefficientlyhandlelargedatasets.BydefaultVTKistunedtowardssmallerdatasets.Forlargedatasetsthereareacoupleofchangesyoucanmakethatshouldyieldamuchsmallermemoryfootprint(lessswapping)andalsoimproverenderingperformance.Theso

2、lutionisto:1.UseReleaseDataFlag,2.TurnonImmediateModeRendering3.UsetrianglestripsviavtkStripper4.UseadifferentfilterormapperEachofthesewillbediscussedbelow.UsingReleaseDataFlagBydefaultVTKkeepsacopyofallintermediateresultsbetweenfiltersinapipeline.Forapipelinewithfivefilters

3、thiscanresultinhavingsixcopiesofthedatainmemoryatonce.ThiscanbecontrolledusingReleaseDataFlagandGlobalReleaseDataFlag.IfReleaseDataFlagissettooneonadataobject,thenonceafilterhasfinishedusingthatdataobject,itwillreleaseitsmemory.Likewise,ifGlobalReleaseDataFlagissetonANYdatao

4、bject,alldataobjectswillreleasetheirmemoryoncetheirdependentfilterhasfinishedexecuting.ForexampleinTclandC++#TclvtkPolyDataReaderreader[readerGetOutput]ReleaseDataFlagOn//C++vtkPolyDataReader*reader=vtkPolyDataReader::New();reader->GetOutput()->ReleaseDataFlagOn();or//C++vtk

5、PolyDataReader*reader=vtkPolyDataReader::New();reader->GetOutput()->GlobalReleaseDataFlagOn();WhileturningontheReleaseDataFlagwillreduceyourmemoryfootprint,thedisadvantageisthatnoneoftheintermediateresultsarekeptinmemory.Soifyouinteractivelychangeaparameterofafilter(suchasth

6、eisosurfacevalue),allthefilterswillhavetore-executetoproducethenewresult.Whentheintermediateresultsarestoredinmemory,onlythedownstreamfilterswouldhavetore-execute.Onehintforgoodinteractiveperformance.Ifonlyonestageofthepipelinecanhaveitsparameterschangedinteractively(suchast

7、hetargetreductioninadecimationfilter),onlyretainthedatajustpriortothatstep(whichisthedefault)andturnReleaseDataFlagonforallothersteps.UseImmediateModeRenderingBydefault,VTKusesOpenGLdisplaylistswhichresultsinanothercopyofthedatabeingstoredinmemory.Formostlargedatasetsyouwill

8、bebetteroffsavingmemorybynotusingdisplaylists.Youcanturnoffdisplaylistsbytu