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18Chapter1printedsurgicalguideshavebeenprovenforapplicationsinandoutsideoralandmaxillofacialsurgerysuchasreconstructivetraumasurgerykneesurgeryandspinalsurgery22–24Duringopenreconstructivecraniosynostosissurgery3Dprintedsurgicalguidescanaidthesurgeoninperformingthereconstructionaccordingtotheplanningandfacilitateapreciseandrapidreconstruction25Anoptimalfunctionalandaestheticresultcanbeachievedbecausethesubjectivityofintraoperativebonefragmentplacementisminimized212627Inpart3and4ofthisthesistheuseof3Dprintedsurgicalguides willbeevaluatedandcompared toother transfermethodsAUGMENTEDREALITYAugmentedreality(AR)isa visualization technique todisplay virtualelementsintothe‘realworld’.AugmentedrealityisacollectivetermformanyapplicationsandmethodsForinstanceARcanbeusedtoplacevirtualcontentontoaphotooravideo ThisaddedvirtuallayercouldshownavigationdirectionsonasmartphoneorenhanceyourfacewithpuppyearsonaSnapchatphotoHowever,therearemanyotheroptionstoachieveARWhenasemi-transparentdisplayisusedtocreateARitbecomespossibletoshowvirtualcontentdirectlyintotherealenvironmentThismethodisusedforexampleincockpitsoffighterplanesandhelicopterstohighlightenemytargetsAnevenmoresophisticatedARtechniqueusesahead-mounteddisplay(HMD) with twosemi-transparentdisplays Thelatterhastheadvantageofalwaysbeingconsistentwiththeuser’ssightandthevirtualcontentcanbeviewedinreal3DbyusingstereoscopicviewThistechnologyreallyenablesthefusionof3DvirtualobjectswiththerealenvironmentAlthoughARisconsideredamoderntechnologythefirstARheadsetwasdesignedasearlyas1968IvanSutherlandfromHarvardUniversitydevelopedanARheadsetandattachedittotheceilingofhislaboratory28(Figure6)Withaflexiblemechanicalstructurehewasabletomeasuretheuser’sheadpositionItwasthereforealsonamedthe‘TheSwordofDamocles’.29WithaspecialandexpensiveNASAcomputer,Sutherlandpreciselycalculatedhow theuserlooked atvirtual3DobjectsFromthishecoulddisplaywire-frameimagesof3Dobjectsat30framespersecond(whichisonlyhalfthespeedoftoday’smodernARdevices)In1990TomCaudellwaslookingforsolutionstoimprovethecomplexprocessofaircraftmanufacturingatBoingCaudelldevelopedaHMDtovirtuallydisplay
