別紙41(課程博士(英文))Date ofsub111ission (1nonth day, year): Jan11a圷 7th、 2022
DepaTtment ofcomputel
Sclence a11d 11nglneerln合、pplicatlt's nametudent Φ Numb引

D巧33巧Supe氏イSors

Kowa Koida
Michiteru Kitazaki

Masakazu ohara

Ab鈍md (Dodo"
Ti11e of Thesis

hnage C11es for pcNei、'ing depth oflranspare11t and rencct八'e objccts

Approx.800 、vords
Percciving the shape of objects in depth is an essential vlsual funcuon ln da11y life. The
human vlsual system tnes to decompose a reれna11ma号e lnto the expenences of shape,n]otion (if it exists), iⅡUn〕ination, and surface optics. However, this process is not always
Perfect, especlaⅡy when no blnocular cue lS 晉Iven, because thls decomposltion ls an 1Ⅱ・posedProblen]. For this problen〕, a mls・perceptlon of shape son]etimcs accompanles the mls・
Perceptlon of a surface's optics, such aS 冨10sslness and albedo.1t is also kno、vn that percelved
depth of objects is modulated by the surface's optics. These con〕plicated interactlons
between the shape and S山face optics of objects is not an inherent perceptual error of theVisual system, but ratl)er,1ndlcates the perceptua11nference that ls most likely occur. Rccent
Studies have found those n]is・perception associated with specular reaectance is sti11 Poorly
Understood ln other ln]portant optical properties ・ transparency Here,1 focused on two
ImpoTtant surface optlcs; specularlty and transparency and examlned how these optlcal
Propertles affecr human percepuon of three・dlmenslonal shape.1f some blases exlst lnPerception,1 ask what lma号e features could explain any resultin晉 depth perceptlon
Firsdy,1 examined how the human observers estin】ate the depth of the three・dimensional
Objects which were simulated to have different nlaterials by usin号 Computet graphics. The
rendered objects varied in the thickness, bumpiness, motion, transparency, specularreaectivity under photorealistic li号htning enviTonmcnts. observers were asked to rate theOvera11 Convexity of these objects alon号 the depth axis. The results showed that observers
Perceived solid purely transparent obJects as natter than the same obJects rendered wlth
Opaque (nwtte or specular) reaectance properties. These results were consistent across

Changes in thickness, bumpiness,1i号htin号 environments, and dynamic/static stimulus
Presentatlons

Secondly,1 tested how the relative intensity of specular reflection to the transparent
d刀ects a仟Cct depth perceptlon.1n the prevlous expenment,1found that the sumulus lmage
Of 50% specular and 50% transparent objects induced similar depth perception to the loo%
Specular objects. Thus, it is important to know which ratio of specular reaection contributes
to a threshold change depth perceptlon.1n this experiment, varlous ratlos of specularreaections of transparent obJects W"ere Presented. The observers con〕pared the overaⅡthickness along the depth axis of the transparent objects with a textured n〕atte object. The
results showed that addin号 only a smaⅡ ratio (< 5%) of specular reaection to the refractiveConlponent was requlred fot equatin又 Perceived thickness ln depth of the n〕atte obJect, andthe 松tio was almost equalto the specular ratio of the ordinary 冨lass and ice. However, thisSpecular ratio was very different across the li3ht fields, indicatin冨 that the structure ofi11Un〕ination si号nificandy biased the perceived shape of shiny transP雛ent objects relative tomatte opaque objects
FlnaⅡy,1 1nvesU号ated what ln〕a号e cues explalnln名 those observed deptl) percepuons
Across the models l tested, a regional variation in local root・mean・square (VRMS) contrast
Of the ln〕a号e was shown to pr0Ⅵde 号ood predlcuon of percelved depth of the obJects. TheVRMs contrast is a simple second・order ima旦e statistic, and thus easy to compute fron〕 theinla名C and maybe inlplementable in the hun〕an visualsystem.1 also showed that the vRMS
Contrast could be applicable to shapes other than a perfect sphere
The finding of underestimation of the perceived depth of the transparent objects, along withthe overesumation of the specular obJects,1S particularly lmportant ln the fleld of materialPercepuon. Many studies of nlatenal perceptlon have focused on the perceptlon of the matenal
itself, such aS 号10ssiness (related to reaective li号ht) and transparency (related to refractive li琴ht)

In my study however,1 examlned how shape perceptlon was modulated by reaecuve/refractlve
Opucal propertles' Thls expenmental parad唱m used ln my study ls also apP11Cable to othermaterial propertles,1ndudln号 Seml・transparency, chromatlclty, and other complex matenals
1[ was also shown that perceived depth can be explained by vRMs contrast re号ardless of thematenals,1ndudlng matte, glossy, and transparent matenals. Thus, many complex surfaces
Could be reproduced by comblnln号 relevant lmage・based lnformanon t0菖ether. AlthoU留hfurthet examination of the model and perception is needed, the model of vRMs contrast、vould be helP丘11 for industry applications that need to control the appearance of products
If thc industry stakeholder wants to n〕odify the appearance of the shape by chan号in号 Surface
Coating and printing, the vRMs contrast model could be a good index to this end