简介:Thispaperpresentsanewclassofsurfacesthatgivetwoquitedifferentappearanceswhentheyareseenfromtwospecialviewpoints.Theinconsistentappearancescanbeperceivedbysimultaneouslyviewingthemdirectlyandinamirror.Thisphenomenonisanewtypeofopticalillusion,andwehavenameditthe"ambiguouscylinderillusion",becauseitistypicallygeneratedbycylindricalsurfaces.Weconsiderwhythisillusionarises,andwepresentamathematicalmethodfordesigningambiguouscylinders.