Ian Mallett (me), Cem Yuksel · Ian Mallett (me), Cem Yuksel University of Utah, USA. Background /...
Transcript of Ian Mallett (me), Cem Yuksel · Ian Mallett (me), Cem Yuksel University of Utah, USA. Background /...
Background / Motivation
● BRDFs describelight scattering
● Extremely importantto realism
● Measured data is realistic– e.g. Matusik et al. 2003
Background / Motivation
BRDF Data TableBRDF
Parameterization
● What parameterization (mapping of data to BRDF's angle space) should we use?
θin
φin
θout
Background / Motivation
● Literature lacks general methods to compare and generate parameterizations!
Contributions
1. Framework to generate and evaluate parameterizations
2. Provide example parameterization and analysis
3. Discuss related technical and theoretical issues
Mathematical Framework
● Want parameterization to importance-sample BRDF:
γ is angle state vector (θin,φin,θout,φout)s is parameter vector (s inθ ,s inφ ,s outθ ,s outφ )
● We describe how to formulate this in the paper
d γ
d s∝BRDF (γ)
d γ
d s∝ BRDF (γ)
Example Parameterization
● Fit a quadratic Bézier curve for each table axis
P1
P0
P2
Effect on BRDF data spacing:Higher density near specular plane (green/blue axes)
Example Parameterization
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
chro
me-
stee
ltu
ngst
en-c
arbi
dess
440
stee
lch
rom
ebl
ack-
obsi
dian
alum
iniu
mbr
ass
blue
-met
alli
c-pa
int2
spec
ular
-bla
ck-p
heno
lic
hem
atit
esi
lico
n-ni
trad
ere
d-m
etal
lic-
pain
tgo
ld-m
etal
lic-
pain
t3co
lor-
chan
ging
-pai
nt3
blac
k-ph
enol
icgr
ease
-cov
ered
-ste
elni
ckel
gree
n-m
etal
lic-
pain
t2co
lor-
chan
ging
-pai
nt1
frui
twoo
d-24
1pv
csp
ecia
l-w
alnu
t-22
4bl
ack-
oxid
ized
-ste
elco
lor-
chan
ging
-pai
nt2
natu
ral-
209
dark
-spe
cula
r-fa
bric
ipsw
ich-
pine
-221
cher
ry-2
35sp
ecul
ar-b
lue-
phen
olic
spec
ular
-gre
en-p
heno
lic
gold
-met
alli
c-pa
int2
colo
nial
-map
le-2
23bl
ack-
soft
-pla
stic
gree
n-m
etal
lic-
pain
tal
um-b
ronz
evi
olet
-acr
ylic
two-
laye
r-go
ldda
rk-b
lue-
pain
ttw
o-la
yer-
silv
erpu
rple
-pai
ntsp
ecul
ar-v
iole
t-ph
enol
icsi
lver
-met
alli
c-pa
int
blue
-met
alli
c-pa
int
gree
n-ac
ryli
cbl
ue-r
ubbe
rgr
een-
fabr
icye
llow
-mat
te-p
last
icgo
ld-m
etal
lic-
pain
tre
d-ph
enol
icsp
ecul
ar-m
aroo
n-ph
enol
icli
ght-
brow
n-fa
bric
blac
k-fa
bric
blue
-acr
ylic
blue
-fab
ric
gold
-pai
ntsi
lver
-met
alli
c-pa
int2
red-
plas
tic
pick
led-
oak-
260
gree
n-pl
asti
cda
rk-r
ed-p
aint
silv
er-p
aint
nylo
npo
lyur
etha
ne-f
oam
mar
oon-
plas
tic
red-
spec
ular
-pla
stic
red-
fabr
ic2
gray
-pla
stic
spec
ular
-red
-phe
noli
cav
entu
rnin
esp
ecul
ar-w
hite
-phe
noli
cli
ght-
red-
pain
tpe
arl-
pain
tw
hite
-pai
ntpi
nk-j
aspe
rw
hite
-dif
fuse
-bba
llye
llow
-pla
stic
delr
insp
ecul
ar-y
ello
w-p
heno
lic
viol
et-r
ubbe
ral
umin
a-ox
ide
spec
ular
-ora
nge-
phen
olic
whi
te-m
arbl
ete
flon
gree
n-la
tex
neop
rene
-rub
ber
yell
ow-p
aint
oran
ge-p
aint
pink
-fab
ric2
pink
-fel
tye
llow
-phe
noli
cpi
nk-p
last
icre
d-fa
bric
poly
ethy
lene
whi
te-f
abri
c2pu
re-r
ubbe
rbe
ige-
fabr
icw
hite
-acr
ylic
pink
-fab
ric
whi
te-f
abri
c
Bezier
Uniform
Identity
Higher-OrderReconstruction Filtering
● Important for measured data
● We suggest cubic B-spline– Good results
– Efficient GPU implementation (Sigg and Hadwiger 2005)
Conclusion
● Propose new mathematical framework to generate and analyze parameterizations
● Validate our approach by generating and analyzing an example parameterization
● Discuss higher-order filtering for measured BRDFs
External Image Sources
● BRDF picture: Derived from https://en.wikipedia.org/wiki/Bidirectional_scattering_distribution_function#/media/File:BSDF05_800.png
● BRDF diagram: remade from http://cybertron.cg.tu-berlin.de/rapid_prototyping_11ws/rp_brdf/img/reflection_t.png
● University of Utah and CGI images adapted from respective websites