FASE 3: Mejora continua de procesos

T he aim of th is th e s is is to classify n o rm a l h u m a n facial

v a ria tio n a n d g e n e ra te sy ste m s th a t a re su ita b le for g en etic a n aly sis.

H ence th e first objective w as to e s ta b lis h a reliab le m e th o d for

collecting facial d a ta from v o lu n te e r s u b je c ts. T h en c am e th e

in v estig atio n of su ita b le m eth o d s, u s in g co n v en tio n a l a n d novel

a p p ro a c h e s for th e a n a ly sis a n d c lassificatio n of facial fe a tu re s. T his

c h a p te r pro v id es a n overview of th e in itial d a ta collection p ro c e d u re

a n d th e g e n eral a n a ly sis of th e face d a ta to g e th e r w ith th e stu d y of

specific poly m o rp h ic facial fe a tu re s.

3D face d a ta h a s b een collected w ith two ty p es of o p tical

su rfa c e s c a n n e r. T hese d a ta a re briefly a s s e s s e d from th e p o in t of

view of q u a lity a n d also in te rm s of th e feasibility of ach iev in g th e

o u tlin e d objectives. Q u a n tita tiv e a n d q u a litativ e m e th o d s of facial

c lassificatio n a re explored a n d in v estig ate p a rtic u la r fe a tu re s a s well

a s g e n eral p ro p e rtie s of th e face; th e ir relative m e rits a n d a p p lic a tio n s

for genetic a n a ly sis a re d isc u sse d . The q u a n tita tiv e a p p ro a c h ta k e s

two lin es, t h a t of a n overall ju d g e m e n t of th e sy m m etry of th e face a s

well a s a n a ly sis of a localised fe a tu re in te rm s of th e degree of

p ro tru s io n of th e m an d ib le. Q u alitativ e m e th o d s a re d e sc rib e d w hich

c h a p te r c o n c lu d e s w ith a n ev alu atio n of th e rep ro d u c ib ility of th e se

a n aly tic al p ro c e d u re s.

4.1 C ollection o f 3D data se ts

3D su rfa c e d a ta from th e face w ere collected from ran d o m ly

re c ru ite d v o lu n te e rs u s in g th e two ty p es of o p tical su rfa c e sc a n n e r,

d e scrib e d in C h a p te r 3.

4.1.1 S c a n d a ta from fixed o p tical su rfa c e s c a n n e r

More th a n 60 0 in d iv id u als w ere sc a n n e d u s in g th e fixed

o p tical su rfa c e sc a n n e r. F o u r s e p a ra te s c a n s w ere m a d e of e ac h

in d iv id u al; full face, m id face a n d one of e a c h e a r (Fig 4.1). T he h eig h t

of th e c h a ir w as a d ju s te d to m ax im ise th e a re a of th e face sc a n n e d .

T he in d iv id u al w as aligned vertically a g a in s t th e h e a d r e s t a n d a sk e d

to close th e ir eyes. The c h a ir w as ro ta te d m a n u a lly to c h ec k th a t th e

fa n n e d la s e r strip e p ro jected vertically alo n g th e m id lin e profile of th e

face. The video g ain w as a d ju s te d a cc o rd in g to b a c k g ro u n d lighting

a n d sk in to n e, g enerally to a ro u n d 125 u n its , b u t slig h tly h ig h e r for

s u b je c ts w ith d a rk e r sk in to n e. T he full-face s c a n b e g a n a t th e left

e a r a n d th e c h a ir w as ro ta te d an ticlo ck w ise 250° u n d e r c o m p u te r

c o n tro l to fin ish ap p ro x im ately a t th e rig h t e ar, c a p tu rin g d a ta a t

o n e-d eg ree in te rv als.

T he m id-face s c a n w as ta k e n 30° e ith e r sid e of th e m idline w ith

d a ta c a p tu re d a t every 0.25° (Fig 4.2). T he raw d a ta for e a c h sc a n w as

B

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) )

jy'm

F igu re 4 .1 Raw d a ta (.Ism ) o b ta in e d from fix e d o p tic a l su r fa c e s c a n n e r A- F u ll-fa ce (f) s c a n , B- M id -face (n) s c a n , C- R ig h t ear (r) s c a n , D- L eft ear (1) s c a n .

;

B

F ig u re 4 .2 A- D e n s ity o f d a ta p o in ts c o lle c t e d from a fu ll-fa c e s c a n , w h er e t h e d a ta are c o lle c t e d a t 1° in te r v a ls o n r o ta tio n o f t h e s u b je c t. B D e n s ity o f d a ta p o in ts c o lle c t e d from a m id -fa c e s c a n , d a ta c o lle c t e d a t 0.25®

c o -o rd in a te s of th e 4 0 ,0 0 0 d a ta p o in ts collected from a sc a n . E a rs

w ere s c a n n e d a t th e sa m e re so lu tio n a s th e full face sc a n s .