外文翻译专用服装三维CAD模型.docx
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外文翻译专用服装三维CAD模型.docx
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外文翻译专用服装三维CAD模型
外文原文
Dedicated3DCADforgarmentmodelling
Abstract
Whileconsiderableprogresshasbeenmadeinfabricmodellingtechniques,whichcouldbeusedingarmentcomputeraideddesign(CAD)systems,lessattentionhasbeenpaidtothewayinwhichgarmentsmightbespecifiedinaCADsystem.Thefinalshapetakenbyagarmentisoftenachievedthroughtheincorporationofdarts,seams,edges,stiffeningpadsandlocalstretchofthefabric.Inordertogaincredibility,CADsystemsshouldhavetofunctionallyhandlethelevelofcomplexitynormallyfoundingarmentassembliescombinedwithasimpleinterfacetospecifytheconstructionaldetail.Differentconceptualapproachesarepossible.Givenanaccuratedrapealgorithm,garmentblockpatternsinachosenfabriccouldsimplybeanchoredorattachedaroundthemannequininordertoachieveavisualisationofagarment.Ifchangeswerenecessary,theuserwouldalterthe2Dpatternsandre-runthevisualisation.Analternativeandpossiblymoreproductiveapproachwouldbetospecifyin3D,withadvanceddrawingtools,the3Dshaperequired.Processingofthe3Dgarmentpieceusingexpertruleswouldindicatethe2Dshapeandconstructionaldetailrequiredtoachievethefinalform.ThispaperdescribesaCADsystemthatisunderdevelopmentandwhichaimstofacilitateboththeapproaches.
Keywords:
CAD;Garmentdesign;Flattening;Draping
1.Introduction
Computeraideddesign(CAD)isnowanestablishedtechniqueforgeneratingpracticaldesignsformostengineeringapplications.Earlysystemsweresimplyareplacementfordraftingboardsanddrawingtools.However,modernCADsystemsincorporatemanyanalysistoolstoassistdesignersinoptimisingdesignsortestingthefunctionalityoftheirdesigns.Inaddition,manufacturinginformationcanbegeneratedefficientlyfromCADdesigns.Thedevelopmentofcomputersystemstoaidthemanufactureofgarmentshasbeenratherpiecemealtodate.Designsystemshaveconcentratedonthevisualisationofgarmentsandtheneedtoefficientlycreateanimageofadesign.Suchsystemshaveprovenveryeffectivewithcompanieswhomanufacturegarmentsforlargeretailorganisationswherevolumesarelargeanddesignshavetobevettedbybuyersfromtheretailer.Theabilitytoquicklytrydifferentcoloursandtexturesisinvaluableinsuchcircumstances.Also,suchsystemsarecapableofgeneratingprototypetextileprintsusingthelatestprintertechnology.Inaddition,thereisahighdegreeofautomationavailableinsubsequentmanufacturingprocesseswhichnest2Dpatternsandgeneratecutterheadpathinformationforlargecuttingtables.
Thereremainthreeareaswherecomputerassistancehasmetwithlittleornosuccess.
1.The3Dspecificationofacompletegarment.
2.Thecreationof2Dpatterns.
3.Accuratesimulationofgarmentvisualisationsensitivetofabrictypeandconstructionaldetail.
Thelackofdevelopmentintheseareashasresultedintheinabilityofcompaniestotrulyadoptacomputerintegratedapproachtodesignandmanufacture.Thepurposeoftheworkdescribedhereistoofferapossibleconfigurationforsuchanintegratedapproach.Thiswillhighlighttheimpactasregardstheuserinterfaceandidentifythecoretechnologiesrequiredtopromotethisintegration.
2.Thepresentsituationandlimitations
ThepresentsituationformostgarmentmanufacturingcompanieswhichproducemediumtolargebatchescanbedescribedbyFig.1.Designersoriginatedesignsbasedontheirowncreativitysubjecttocurrentfashiontrendsandthetargetmarket.Theirdesignspecificationisusuallyintheformofapaperdrawingrepresentingavisualisationofthegarment.Sometimesattachedtothisdrawingmaybeasmallsampleorswatchofthefabricfromwhichthegarmentistobemade.Itisimportanttonotethatdesignsinthisformarenotregardedaseitherafullgarmentconstructionalspecificationoranexact2Dviewofthe3Dgarmentproduct.
Consequently,thismeansofcommunicatingdesignstendstobeinformalbutsufficientlydetailedforthenextmanufacturingstagetoproceed.Themajorlimitationsofthissituationaretwofold.
1.Thesubjectivenatureofhowthepatterntechnologistinterpretsthedesignstoproducetheactual2Dpatterns.
2.Secondly,thelowacceptanceratesthatareachievedattheassessmentstage.
Thisresultsinnotonlyalargenumberofrejectedsamplesbutalso,moreimportantly,losttimeanddiversionofeffort.
3.Computerintegratedapproach
TheapproachproposedhereispresentedinFig.2.Thisblockdiagramdepictsthecoreelementsrequiredforanintegratedapproach.Thekeyelementswhichhavepreventedsuchanintegratedapproachfrombeingadoptedtodateare
●aneffectivedesigninterfacefordesignerstocreate3Dspecificationsofgarments;
●arobustpatternflatteningmodule;
●anaccuratedrapeengine.
Foranintegratedmanufacturingapproachtobesuccessful,allthreeofthesedifficultelementsmustbeadequatelyaccomplished.Theseelementswillnowbeconsideredin
moredetail.
3.1.Designinterface
Thedesignfunctioninthegarmentindustryisacreativeandartisticprocesscomparedwiththeequivalentengineeringfunction.Soanydesignsystem,whichisofferedtodesigners,mustnotbeperceivedasrestrainingcreativetalentorconstrainingartisticflair.However,designersdooperatewithincertainparametersintermsofcostandfunctionalityofthefinalproduct.Superimposedonthesedifficultiesisthecomplexandamorphousnatureoftheshapeofthegarmentwhenworn.Preciselywhatshapeshouldthedesignerattempttoconveytoacomputersystemviathedesigninterface?
Theapproachproposedhereistoprovidethedesignerwithaninitialdesigninterfacethatwillenableafull3Dspecificationofthegarmenttobecreated.Thisspecificationmustbecapableofprovidinganaccuratesurfacedescriptioninareaswherefitisimportant,i.e.wherethegarmentisincloseproximitywiththeunderlying
mannequin.Suchsurfacedescriptionsmustbecapableofspecificationusingexistingmathematicaltechniquesusingasuitableinterface.However,itwouldbeinappropriateforadesignertodescribethe3Dgeometrytakenupbyareasofthegarmentwherethefabricdrapes.CurrentCADsystemswouldcertainlybeabletoaccuratelyrepresentthesedrapedshapesusingtechniquessuchasthemanyformsofbicubicsurfaces[1],butitwouldbeunreasonabletoexpectadesignertotediouslyspecifysuchshapes.Secondly,inordertoaccuratelypredictorvisualisetheshapetakenupbythe
garment,thedesignerwouldhavetohaveaverycomprehensiveknowledgeofthefabricbehaviour.Forthepurposesofthedesigninterface,itisproposedthatrepresentationssuchasthatshowninFig.3(a)wouldbeacceptableforinitialgarmentspecificationasastylisedformwhichwouldbecapableofincorporatingalloftheconstructionaldetailnecessaryformanufacture.
Whilenotbeinganattempttoaccuratelysimulatethe3Dappearanceofthegarmentatthispoint,thedesigninterfaceshouldembodyfunctionalitytoimplicitlydefineallotheraspectsofthegarmentspecification.Forinstance,iftwoabuttingpanelpiecesaredefinedthenthereshouldfollowarequirementtonominatehowthesepanelsaretobejoined.Alsofabrictypesshouldbedefinedforallpanels.Ineffect,thisstageshoulddefinealloftheparametersforasubsequentdrapesimulationtoproceed.
The3Dsurfacerepresentationofthegarmentdisplayedatthisstagehastwoimportantroles.Firstly,itprovidesa3Dframeworkwithinwhichpanelrelationshipscanbefullydefinedintermsofthegarmentcomposition.Alsoitprovidesareasonablestartingpointfordrapesimulations.Thus,panelnodeswhichareusedtodefineapanelwillhaveatriplerepresentationasfollows.
1.Asanodeintheinitial3Dstylisedpanel.
2.Asanodeonthe2Dflatteningofthepanel.
3.Asanodeinthedrapesimulationofthepanel.
3.2.Patternflattening
Someattemptshavebeenmadetoprovidesoftwaretogenerate2Dpatternsforgarments[2,3].However,thesehavemetwithlimitedsuccessbecauseoftheprerequisitethatafull3Dspecificationmustpreviouslyexistinorderfora2Dpatterntobederived.Also,therehastobeanintelligentexaminationofthegarmentspecificationtoestablishhowcriticalthepatternflatteningprocessshouldbeinconformingtotheoriginal3Dsurface.Theauthorsproposethatthegarmentspecificationshouldbeintelligentlypartitionedintofitanddrapeareas.Theprimaryindicatorofwhetheranareaofagarmentisineitherofthesetwocategoriesisthe
offsetwithrespecttounderlyingmannequinandthedegreetowhichthegarmentisforcedtobeconstrainedtothisoffset.
Dependingonthispartitioning,theflatteningprocesswouldflattenfittedareasdifferentlyfromdrapedareas.Anotherinfluentialfactorwouldbethematerialcharacteristicsofthefabricinvolved.Thisismademoredifficultbytheanisotropicnatureofmostfabricsduetotheirwovenorknittedconstruction.Finally,itisimportantthat2Dflatteningspecificationsdonotsimplyconsistofa2Doutline.Thereneedstobeafullinteriordescriptionofhowthegarmentismappedfrom3Dto2Dwhichwillenablethereverseprocesstobeachievedwhendrapingisconsidered.Theauthorshavedescribedelsewhere[4],aflatteningalgorithmwhichoperatesonapolygonlistof3Dtrianglestoprovide2Dflattening.Thisalgorithmiscapableofhandlingthearbitrarysitingofseamswhichcouldinvolvedartsorgussetsdependingonthenatureofthecurvatureinvolved.
3.3.Drapeengine
Thismoduleshouldbecapableoftakingthefollowinginformation:
●Ageometricdescriptionofa2Dpattern(includingsufficientinteriorpointsandconnecti
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