ngha cc thng s trong vt liu Vray 2.0Diffusey l mu sc ca b mt vt
th, phn x v khc x mu sc c th nh hng n s xut hin hnh nh ca mu sc ny.
iu ny rt quan trng bi v bn phi hiu rng khng c vt th no trong th gii
thcl mu trng tinh khit RGB (25.255.255) hay l mu en RGB (0,0,0).
Khi to ra mt loi vt liu mu trng hoc en, hy thit lp cc gi tr mu trng
RGB (245.245.245) / en RGB (2,2,2). Nu bn lm cho mt vt th l mu en
hoctrngtinh khit , bn s nhn thy rng s khng c s tng phn mu sc ca vt
th.Roughnessc s dng m phng nhm b mt bng cch kim sot cch b mt phn
chiu thng quanh sngtrc tip.ReflectionReflecty l ch s phn nh s phn x
nh sng vt th. Trng RGB (255.255.255) l phn x hon ton ( nh gng ) v
mu en RGB (0,0,0) l khng phn x. Bng cch s dng mu sc thay v mu n hoc
trng, bn s nhn c phn x mu. Bn thng s s dng mt gi tr mu no xc nh sc
mnh phn x v khng c gi tr ng hay sai, do bn s phi c s suy lun tt nht
. Tuy nhin, hnh sau y c th c s dng nh mt ti liu hng dn.
Kim loiNhm bng tinh khit, 80 87%Nhm m, 80 87%Nhm bng, 65 75%Nhm
Matte, 55 75%Nhm sn, 55 65%Chrome bng, 60 70%Thp, 25 30%ng nh bng ,
60 70%ng thau nh bng , 70 75%Cc vt liu khcg si sng (bng), 25 35%g
si ti (bng), 10 15%G Vn, 25 40%Giy trng, 70 80%Granite, 20 25% vi,
35 55% bng (Ty thuc vo mu sc), 30 70%nh sng bng va, 40 45%Tng va ti
(Rough), 15 25%B tng (Rough), 20 30%Gch mi, 10 15%Gch trng, 75
80%Thy tinh, 5 10%Men trng, 65 75%Sn mi, trng 80 85%Gng bc, 80
88%Gng nh bng, 92 95%Mu sc cng nh hng n cng phn chiu. Mu trng phn
chiu ton b quang ph mu trong khi mu en hp th tt c mu sc.White, 75
85%nh sng mu xm, 40 60%Trung mu xm, 25 35%Ti mu xm, 10 15%nh sng mu
xanh, 40 50%Mu xanh m, 15 20%nh sng mu xanh l cy, 45 55%Mu xanh m,
15 20%nh sng mu vng, 60 70%Mu nu , 20 30%nh sng , 45 55% thm, 15
20%Mu en, 2 5%Fresnel reflectionsHu ht cc vt liu tr kim loi c mt s
phn x Fresnel, lm cho s phn x mnh m gc bn cnh nhng yu khi nhn pha
trc din. Mt v d tt v iu ny s c xem xt ti mt mn hnh vi tnh . Nu bn v
tr ca mnh bn ca mn hnh v nhn vo knh, bn r rng s thy mt s phn x ca
mi trng, nhng nu bn v tr ca mnh trc tip pha trc bn s nhn thy rng
phn x gim.Phn x Fresnel ln u tin c nghin cu bi nh vt l ngi Php
Augustin-Jean Fresnel (1788-1827). Fresnel nghin cu hnh vi ca nh
sng v lm th no n c lan truyn bi cc i tng khc nhau.
Fresnel IORIORl vit tt ca ch s khc x v c s dng o lng lm th no nh
sng khc x qua mt b mt tng i so vi gc nhn, hi kh hiu mt cht, nhng bn
hy c tip. t mt thanh g trong mt b nc, ch lm th no thanh un cong bn
di b mt nc? Khi nh sng i qua b mt nc, n thay i tc v un cong.IORcng
c th c s dng o lng s phn chiu v nh sng phn chiu mt b mt tng i so vi
gc nhn v mc d c tnh ton theo mt cch hi khc nhau, chng thng t l
thun. Do , cng mt gi tr IOR cho c hai gi tr phn x v khc x. y l l do
ti sao mc nh n thng kha ch IOR . Mt cng thc c gi l nh lut Snell c s
dng m t mi quan h gia gc ti v khc x trong cung cp cho bn cc ch
sIOR.
Bn c th tm thy bngIORnhiu trn internet v tt c h u cung cp cho cc
gi tr khc nhau i vi vt liu trong th gii thc. S tht l khng c gi tr
thc t, n ph thuc hon ton vo cht liu v c im ca n chng hn nh bi bn,
try xc r st . Nhng nu bn cn mt gi tr di y l mt vi v d ph bin dnh
cho bn.Nc 1,333Knh 1,5 1,6Vin kim cng 2,13Hp cht vt liu nh g, , b
tng 3 4Nha 5 8Nu IOR ca 1 c s dng, sau nh sng phn chiu / i / qua b
mt m khng thay i hng, c ngha l n c mt ging nh khng kh. Vt liu nh
knh cho php nh sng i qua, m cn c phn x. T l gia phn x v khc x ph
thuc vo gc nhn.Bn c th kim sot s phn x Fresnel bng cch s dng mt bn
falloff. Tuy nhin, phng php ny c bit n s brenderchm hn so vi vic
chnh thng s Fresnel.
Mt bn falloff s to ra mt qu trnh chuyn i gia mu sc pha trc v mu
sc bn (pha trc mc nh l mu en, hai bn l mu trng). N s s dng cc loi
falloff xc nh loi phn x. Vi Fresnel c la chn, cc mu en s c b tr trn
gc v n s chuyn sang mu trng khi n tr thnh mt gc nhn bn cnh. Bn c th
thay i falloff bng cch iu chnh gi tr IOR, hoc bng cch iu chnh ng
cong u ra, hoc c hai.Highlight glossiness (Cao quang)Nhng im ni bt
th gii thc l phn x ca ngun nh sng v cc i tng xung quanh. Trong ha
my tnh, c hai phng php khc nhau tnh ton hiu qu ca vic tng t. u tin
l lm cho khng c s phn bit gia nh sng v cc i tng. Th hai l iu chnh
thng s ring cho cc i tng n.Theo mc nhHighlight glossiness bkha bi v
trong th gii thc, s khng c s khc bit. Highlight glossiness c bit n
nh l gng. N c s phn x ca mt nh sng trc tip v thm n vo b mt vt
liu3ds MaxScanline render tnh ton phn x theo cch ny, v mc d cch ny
khng thc t nhng n vn cn a chung bi mt s l do ngh thut.Reflection
glossinessGi tr l 1,0 c ngha l s phn x gng r, gi tr thp hn c ngha l
s phn x m hn. Cng m phn x cng mt thi gian tnh ton.SubdivsKim sot
cht lng ca Highlight glossiness. Nu ch s ca Subdivs l qu thp kt qu
phn x s b nhiu.Use interpolationBn c th s dng cng c lu li thng
sglossiness vtng tc dng hnh.Dim distanceBn c th thit lp khong cch
ti a ca mt tia phn x . V d, nu bn thit lp l 100mm, bn ngoi bn knh
100mm s khng c phn x.Dim fall offThit lp bn knh cho Dim distanceMax
depthiu khin s ln mt tia sng c th phn x.Max depth bng1 c ngha l ch
c 1 s phn x xy ra trn b mt vMax depthbng2 c ngha l 2 s phn x xy ra
trn b mt.Max depthcng cao cnglm tng thi gian render.Exit colorKhi
tMax depth, nh sng s dng li vi mu m bn thit lp. V d , bn s thit lp
mu xanh l cychomt chai thy tinh .RefractionRefracty l ch s c s dng
xc nh cng khc x. Mu trng RGB (255.255.255) l khc xhon tonv mu en
RGB (0,0,0) l khng khc x. Bng cch s dng mu sc thay v mu en trng, bn
s nhn c khc x mu. Bn thng s s dng mt gi tr mu en hay trng xc nh cng
khc x v khng c gi tr ng hay sai, do bn s phi c s suy xt tt nht ca
mnh. Tuy nhin, hnh sau y c th c s dng nh mt ti liu hng dn.
Theo ch mc inh, mu sc phn chiu ng vai tr nh mt b lc nh sng cho
mu sc khuch tn, mu sc phn chiu cng m th mu khuch tn cng m. i vi knh
c phun mu, cch tt nht l iu chnh mu phun thng qua mu khc x. Khi mu
khuch tn c t l mu en (0,0,0) th n s khng to nh hng ti mu khc x. Khi
, bn ang tt mu khuch tn i mt cch rt hiu quIORCh mc cho cc gi tr khc
x (IOR) m t cchnh sngun congkhi n truyn qua mt b mt. Mt gi tr l 1,0
c ngha l nh sng khng thay i hng.GlossinessMt gi tr l 1,0 c ngha l
khc x sc nt r rng, gi tr thp hn c ngha l khc x l m hn. Khc x cng m
th thi gian render cng lu.SubdivsKim sot cht lng
caRefractglossiness . Nu ccSubdivsl qu thp kt qu render s b
nhiu.Use interpolationBn c th s dng cng c lu li thng s glossiness v
tng tc dng hnh.Max depthiu khin s ln mt tia sng c th i qua mt b mt
trc khi dng li. MtMax depthbng1 c ngha rng ch c 1 khc x thng qua mt
b mt v Max depthbng2 c ngha l mt s khc x ca mt s phn x khc c th xy
ra trn b mt vt th. Gi tr cao hn lm tng thi gian render. V d nu bn
nhn qua mt chic ly nc nh hnh di n s c 4 b mt. Mt Max depthbng4 s l
gi tr chnh xc.
Exit colorKhi t Max depth , nh sng s dng li vi mu m bn thit lp.
Bn c th lm gim Max depth gi cho thi gian render nhanh hn v thay vo
da vo gi tr Exit color. V d , bn s thit lp mu xanh l cy cho mt chai
thy tinh .Fog colouriu khin s suy gim ca nh sng khi n i qua b mt vt
th, mu ti hn hp th nhiu nh sng hn trong khi mu sc nh hn khng hp th
nh sng nhiu. ng nhin vt th dy s tr nn t trong sut hn cc i tng mng
hn. Bng cch thit lpFog colourmu xanh l cy, v n c th c p dng cho vic
m phng mu sc ca thy tinh.Fog biasNu c s dng, n s kim sot cch thc c
p dng trongFog colour. Bn c th lm cho phn mng hn ca vt th nhiu hn
hoc t trong sut hn so vi ch mc nh.Fog multiplierSc mnh caFog
colourc iu khin biFog multiplier. Gi tr cao hn s lm cho vt th t
trong sut hn v gi tr thp hn s lm cho vt th tr nn trong sut
hn.Affect shadowsNu c chn, cc vt th s bng trong sut ( bng ca s phn
chiu , v ci bng trong sut ), ty thuc vo mu ca khc x vFog
colourAffect Channels y bn c th ch nh s nh hng bi tnh trong sut ca
ca vt liu. Nu cho vt liu thy tinh, bn s cn phi chn ch ny c phn x v
khc x u c thc hin.DispersionTrong th gii thc, mt tia sng truyn i
thng qua mt i tng b khc x, n s to ra mt hiu ng caustic trong bao gm
mt tia mu sc. Trong Vray 2.0, chng ta c th iu chnh thng s ny, cc
phin bn trc ca V-Ray ch cho php bn mu trng.
AbbeGi tr mc nh ca lng phn tn s c xc nh chnh xc theo quy nh ca
thng s IOR. Bn c th tng hoc gim v l do ngh thut. Tng gi tr c ngha l
phn tn s t v thu hp li trong khi gim gi tr s ly lan ra s phn tn v
lm cho n mnh hn.TypeL vt liu m nh sng sau khi i xuyn qua vt th th
lu li v khuch tn pha trong vt th. Vt liu nh da ngi v sp l mt trong
s nhng vt liu ph bin nht.Back-side colourTheo mc nh, mu sc ca hiu
ng translucency ph thuc vo Fog colour. Tuy nhin, bn c th b sung thm
mu bng cch s dng tham s ny.ThicknessChiu su m xuyn ca tia sng.Light
multiplierKim sot cng ca nh sng nhn thy.Scatter coefficientLng tn x
s xy ra bn trong vt th . 0,0 c ngha l tia sng s c nm ri rc tt c cc
hng , mt gi tr l 1,0 c ngha l tia sng s khng thay i hng ca
n.Forward / backward h siu khin hng phn tn ca mt tia sng, 0,0 c
ngha l tia sng di chuyn ra khi b mt. 0,5 c ngha l tia sng c th di
chuyn v pha trc hoc pha sau. 1,0 c ngha l mt tia sng s di chuyn v
pha b mt.BRDFCc loi BRDF xc nh cc im ni bt v bng phn chiu cho vt
liu. Bn s s dng Ward cho vt liu thp khng g. Blinn v Phong cho nha v
vt liu khng phi kim loi v Blinn i vi nguyn liu chrome. Tc tnh ton
khc nhau cho mi loi vt liu. Phong l nhanh nht, tip theo l Blinn, v
sau Ward. (Phong da trn thut ton Phong shading ca Mr Bi Tng Phong,
l mt trong nhng ngi Vit Nam ni ting v c ng gp ln nht trong lch s ha
my tnh)
SoftenBn c th kim sot vic pha trn gia cc vng sng v ti trong s
phn x, phn chiu.Fix dark glossy edgesNu bn khng mong mun cnh ti xut
hin, s dng iu ny loi b chng.AnisotropyChiu dn ca highlight. Mt gi
tr ca 0,0 c ngha l s phn x l ng hng, c ngha l s phn x l nh nhau
trong tt c cc hng. S m l gin dc, s dng l gin ngang.RotationChiu
quay ca Anisotopy.UV vectors derivationKim sot hng c chn bng cch s
dng knh trc a phng hoc bn .OptionsTrace reflectionsCh ny tt c ngha
l s phn x s khng c truy tm, nhng s ni bt vn s c hin th.Trace
refractionsTurning ny tt c ngha l khc x s khng c truy tm.CutoffKim
sot ngng m phn x / khc x s khng c truy tm. Phn x m hu nh khng ng gp
vo cc mu hnh nh cui cng s khng c truy tm. S dng cao hn cut-off c
ngha l thi gian render nhanh hn. Nu thit lp l 0 thi gian render s
rt chm, cn phi c mt ngng Vray bit khi no dng tnh.Environment
priorityXc nh bn mi trng s c s dng khi bn ghi ln mi trng ca cc vt
liu khc nhau v chng s phn x / khc x nhau.Double-sidedKhi kch hot ch
ny , pha bn kia ca vt th s c ln li. Renderer Scanline b qua cng vic
ny tng tc qu trnh dng hnh. Theo mc nh Vray s khng b cc qua a gic,
mt trong nhng l do l bi v mt pha kia ca vt th vn c th c nhn thy
trong mt phn chiu / khc x.Reflect on back sidei vi vt liu nh thy
tinh, bn s cn phi bt ln c c mt kt qu thc t cc phn x c tnh trn tt c
cc b mt. Tuy nhin iu ny s lm tng thi gian render.Use irradiance
mapTheo mc nh,irradiance mapc s dng tnh ton chiu sng gin tip s
khuch tn ca vt liu.Fog system units scalingCh ny theomc nh skch
hot, s suy gim Fog color tr nn ph thuc vo cc n v h thng. Nu cnh ca
bn khng c v li theo t l vi th gii thc, bn c th nhn c kt qu khng
mong mun vi iu ny.Treat glossy rays as GI raysNu thit lp always ,
bn ang ni vi cc vt liu lun lun s dng cc secondary GI engine tnh ton
cc tia bng, m trong trng hp ny l b nh cache nh sng. V c bn n khng c
s dng tng t nh b nh cache nh sng s dng i vi cc tia bng, nhng bn c
th ch nh ring l nguyn vt liu trong vic s dng ty chn ny.Energy
preservation modeBn c th chn mt cch khc nhau phn phi nh sng gia s
phn x v lp khuch tn. Trong th gii thc, phn x mc lm m mc khuch tn v
khc x gy ra s phn x c th nhn thy khng c 100% gi tr phn x RGB. lm
cho s phn x 100% gi tr phn x RGB, thit lp n sang n sc, nh vy mu
khuch tn khng c nh hng nkt qumu sc phn x .Maps y bn c th thm bn kt
cu kim sot cc tc ng ca mi thuc tnh ca vt liu.Reflect/Refract
interpolation y bn kim sot ni suy phn chiu bng. Cc ty chn l tng t
nh cc ty chn cho cc bn bc x trong cc thit lp render.Nu c gp bt c vn
kh khn no , hy lin lc vi chng ti, hoc li comment bn di . Chng ti s
gii p bt k thc mc no cho bn . Thn !
