Reflect Ance Models
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Transcript of Reflect Ance Models
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Reflectance Models
CS 319
Advanced Topics in Computer Graphics
John C. Hart
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ocal !llum. Conte"t
# Surface point $x% and normal $N%
# i&ht source $S' notL%
( )ector from xto li&ht *source+
( ,ir. incident radianceLi-L$S%
comesfrom$lie /ind direction%
# )ie/ vector $V%
( ,irection from xto *vie/er+
( Reflected radianceLr-L$V% dir.# Reflection vector $R%
R- 0$NS%N( S
# Half/a vector $H%
H- $V2S%44V2S44
N
SR
V
H
$R%
$S%
x
All vectors are unit len&th
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Some Spec$tac%ular Hacs
# ,ecompose 5R,6diffuse2specular
Lr- $fd2fs$S')%%LiNS
# 7hon&8fs- ksma"$VR'%n $NS%
# 5linn8fs- ksma"$NH'%n
$NS%# 5linn n- :7hon& n# ;ot
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Coo=Torrance
# 5ased on Torrance=Sparro/ model
# 7hsicall plausi
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6resnel >ffect
# ? of li&ht reflected increases as *half/aincidence an&le+ hincreases
( ;ormalNof rou&h surface not /ell
defined' so needHinstead
( S and ) nearl constant across surface
( 6resnel effect independent of ;
( ;earl constant across surface
# Affects color of reflected li&ht
( ;ormal incidencesurface color
( Tan&ent incidenceli&ht color
# 7hoto&raphic tric8 place
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6resnel Term
# 6resnel termFcontrols portion of li&htreflected v. portion refracted $1 (F%
# 7hsicall accurate 6resnel function
( 7arameteried
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Rou&hness Term
# Statistical model of li&ht reflectance
# Rou&hness m- RMS of slope
# 5linnBs hac
Dm'c$N'H% - ce"p$(0 m0%
( An&le - cos=1$NH% E'0F( Ar
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5linn v. 5ecman
5linn
5ecman
m- m-1 m-0S
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Geometr Term
# Shado/in&
( !ncident li&ht does not reach material
Gs$N'S'V% - 0$NH%$NS%$SH%# Masin&
( Reflected li&ht does not reach vie/erGm$N'S'V% - 0$NH%$NV%$VH%
# Geometr term - shado/ A;, mas
G$N'S'V% - minGs$N'S'V%' Gm$N'S'V%' 1I
( Clamp to one to eep demoninators in chec
x
Gs Gm G
S
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Coo=Torrance ,emo
m-
m-0$
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Seeli&er Sin
# Model for diffuse reflectance from sin
# Softer appearance than am
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Hair
# 6rom a@ia L a SNN
# Anisotropic
# Kses tan&ent vector T
# ,iffuse anisotropic
fd- sin$T'S%
# Specular anisotropic
fs- $$TS% $TV% 2 sin$T'S% sin$T'V%%n
T
SS
sin$A'B% - sOrt$1=$AB%0%
Chan&' Jin L
Pu' 01
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Hair >"amples
diffuse
spec.' n-1
spec.' n-N
diff2spec
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6ur
# Goldman S9
# Scatterin& of li&ht
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6ur >"amples
scatterin&
opacit
fae fur