7. texture mapping - cgl.ethz.ch · 7. texture mapping 3 idea • add surface detail without...
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7. Tex
ture M
ap
pin
g
7. Tex
ture M
ap
pin
g 2
+ T
extu
re Ma
pp
ing
Mo
tivatio
n
Wire
fram
eM
od
el
+ Lig
htin
g &
Sh
ad
ing
http
://ww
w.3d
ren
de
r.com
/jbirn
/pro
du
ction
s.htm
l
tow
ard
s mo
re re
alism
7. Tex
ture M
ap
pin
g 3
Idea
•A
dd
surfa
ce d
eta
ilw
itho
ut ra
ising
ge
om
etric co
mp
lex
ity
•T
ex
ture
s can
be
ima
ge
so
r pro
ced
ure
s
•T
ex
ture
s can
be
2Do
r 3D
7. Tex
ture M
ap
pin
g 4
Exa
mp
les –Im
ag
e T
ex
ture
s
Flytastic
II (ww
w.e
nd
ox
on
.ch)
+
7. Tex
ture M
ap
pin
g 5
Exa
mp
les –Im
ag
e T
ex
ture
s
7. Tex
ture M
ap
pin
g 6
Exa
mp
les –B
um
p M
ap
7. Tex
ture M
ap
pin
g 7
Exa
mp
les –B
um
p M
ap
in H
ard
wa
re
7. Tex
ture M
ap
pin
g 8
Exa
mp
les –D
ispla
cem
en
t Ma
p
7. Tex
ture M
ap
pin
g 9
Exa
mp
les –En
viron
me
nt M
ap
7. Tex
ture M
ap
pin
g 10
Issues
•D
efin
ition
of te
xtu
re co
ord
ina
tes
•S
urfa
ce p
ara
me
trizatio
n
•A
nti a
liasin
g
•T
ex
ture
filterin
g
•Le
vel-o
f-De
tail
•H
ard
wa
re a
ccele
ratio
n
7. Tex
ture M
ap
pin
g 11
Co
ncep
t of T
extu
re Ma
pp
ing
•Fin
d m
ap
pin
gs b
etw
ee
n d
iffere
nt co
ord
ina
te
system
s
•In
vert tra
nsfo
rma
tion
from
tex
ture
co
ord
ina
tes to
ima
ge
pix
el
Tex
ture co
ord
ina
tes
surfa
ce coo
rdin
ates
w(u
,v)=
(x,y,z)
Pix
el coo
rdin
ates
7. Tex
ture M
ap
pin
g 12
An
alytica
l 3D Su
fraces
1. Ke
y to te
xtu
re m
ap
pin
g: P
ara
metriza
tion
→
),
(
),
(
),
(
ts
z
ts
y
ts
x
t s
→
φθ
φφ
θ
φ θ
sincos cos sinsin
sph
ere
:
2. Ma
p p
ara
me
ters to
tex
ture
coo
rdin
ate
s
→
),
(
),
(
ts
v
ts
u
t s
→
)
,(
),
(
vut
vus
v uin
verse
:
7. Tex
ture M
ap
pin
g 13
Ma
pp
ing
a tex
ture o
nto
a sp
here
•U
se lin
ea
r ma
p
+ +=
D
Cv
BAu
φ θ
+
⋅−
⋅=
2/
4/
2/
ππ
πφ θ
v
u
7. Tex
ture M
ap
pin
g 14
Exa
mp
le
7. Tex
ture M
ap
pin
g 15
Pa
ram
etrizatio
no
f Tria
ng
le Mesh
es
•Fin
d te
xtu
re co
ord
ina
tes fo
r vertice
s
•T
ake
no
rma
l or ra
y from
cen
ter o
f gra
vity
Sph
erical co
ord
ina
tes (θ,φ
)
Tria
ng
le vertex
Cen
ter of G
ravity
Pro
ble
ms:
Mu
ltiple In
tersection
s
7. Tex
ture M
ap
pin
g 16
Pro
blem
s
Cra
ig G
otsm
an
et. al.
•O
verla
ps
•T
iny a
nd
larg
e tria
ng
les
–o
ptim
ize co
ord
ina
tes
by m
ovin
g ve
rtices o
n sp
he
re
–co
st fun
ction
(a
rea
, an
gles, o
verla
p)
–fin
d m
inim
um
itera
tively
•T
op
olo
gica
lly no
t a sp
he
re–
cut m
esh
–o
ptim
ize p
atch
es sep
ara
tely
7. Tex
ture M
ap
pin
g 17
Tex
ture M
ap
Tim
We
yriche
t. al.
•T
ex
ture
ma
p co
rresp
on
ds to
pa
ram
etriza
tion
stretch
ed
at n
ose
tipco
mp
resse
d a
t no
se tip
7. Tex
ture M
ap
pin
g 18
Pa
ram
etrizedT
rian
gle M
esh
v 0.131171 -0.113469 0.178314
v 0.130945 -0.114951 0.182474
v 0.130916 -0.115792 0.185402
…vt
0.538446 0.4275
vt
0.550132 0.41427
vt
0.546491 0.427631
…vn
0.609697 0.486474 0.625789
vn
0.799934 0.334347 0.498315
vn
0.942394 0.131824 0.307435
…f 22/209/22 220/210/220 221/211/221
f 21/213/21 219/214/219 220/210/229
f 253/203/253 219/214/219 21/213/21
…
Ve
rtex
po
sition
s
Te
xtu
re co
ord
ina
tes
No
rma
ls
Face
s (trian
gles)
coordNr/texNr/normalNr
OB
J Files:
7. Tex
ture M
ap
pin
g 19
Ra
sterizatio
n
•Fro
m te
xtu
re co
ord
ina
tes o
f vertice
sto
tex
ture
coo
rdin
ate
s of p
ixe
ls
•Lin
ea
r inte
rpo
latio
n in
scree
n-sp
ace
(a
s in G
ou
rau
dsh
ad
ing
):
textu
re so
urce
wh
at w
e g
et
wh
at w
e w
an
t
Ima
ge
s by Fre
do
Du
ran
d
7. Tex
ture M
ap
pin
g
20
Persp
ective Interp
ola
tion
•Lin
ea
r varia
tion
in w
orld
coo
rdin
ate
s yield
s n
on
-line
ar va
riatio
n in
scree
n co
ord
ina
tes:
•P
ersp
ective
inte
rpo
latio
n im
ple
me
nte
d
in to
da
y’s gra
ph
ics card
s
projection
plane
(u0 ,v
0 )
(u1 ,v
1 )
7. Tex
ture M
ap
pin
g 21
Tex
ture Filterin
g
•(u,v)
are
rea
l pix
el co
ord
ina
tes, e
.g. (6.4, 3.7):
]4,6
[map
color=
ne
are
st
]4,7[
]4,6[
]3,7[
]3,6
[
map
ts
map
ts
map
ts
map
ts
color
⋅⋅
+⋅
⋅+
⋅⋅
+⋅
⋅=
3
u
4
67
ss
tt
bi-lin
ear
u
3 4
67
7. Tex
ture M
ap
pin
g 22
Tex
ture M
ap
pin
g in
Op
enG
L
loadImage(&texture_data);
glGenTextures(1, &texId);
glBindTexture(GL_TEXTURE_2D, texId);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB,
w, h, 0, GL_RGB, GL_UNSIGNED_BYTE,
texture_data);
…glBindTexture(GL_TEXTURE_2D, texId);
glBegin(GL_TRIANGLES);
glTexCoord2f(u0 ,v0 ); glVertex(x0 ,y0 ,z0 );
glTexCoord2f(u1 ,v1 ); glVertex(x1 ,y1 ,z1 );
glTexCoord2f(u2 ,v2 ); glVertex(x2 ,y2 ,z2 );
glEnd();
→T
uto
r
]10[
,K
∈vu
mnh
w2
,2
==
7. Tex
ture M
ap
pin
g 23
Enviro
nm
ent M
ap
•M
eth
od
to re
nd
er
refle
ctive o
bje
cts
•C
om
pu
te in
terse
ction
o
f refle
cted
ray w
ithsu
rrou
nd
ing
sph
ere
•T
ake
pa
ram
ete
r valu
es
of in
terse
ction
a
s tex
ture
coo
rdin
ate
s
n
(θ,φ)
7. Tex
ture M
ap
pin
g 24
Exa
mp
les
•R
efle
ction
ma
pp
ing
usin
g O
pe
nG
L
7. Tex
ture M
ap
pin
g 25
Cu
be M
ap
pin
g
•S
ph
ere
can
be
rep
lace
d b
y cub
e
•S
imp
lify com
pu
tatio
ns
7. Tex
ture M
ap
pin
g
26
Linea
r Ma
pp
ing
•U
ses o
bje
ct or e
ye co
ord
ina
tes
•(In
)de
pe
nd
en
t of tra
nsfo
rms
•C
an
be
use
d to
com
pu
te d
istan
ce fro
m o
bje
ctsy
x
-x
z-z
7. Tex
ture M
ap
pin
g 27
An
Exa
mp
le
•M
ap
pin
g o
f dista
nce
s from
lase
r ran
ge
da
ta
7. Tex
ture M
ap
pin
g 28
Pro
jective Tex
tures
•G
en
era
lize te
xtu
re co
ord
ina
tes to
a 4D
ho
mo
ge
ne
ou
s vecto
r (u, v, r, q
)
•T
ex
ture
ma
trix co
mp
ute
s full 4
x4
tran
sform
to
(up, v
p) use
d fo
r tex
ture
loo
kup
•T
ex
ture
ima
ge
can
be
pro
jecte
d in
de
pe
nd
en
t o
f view
ing
pro
jectio
n
•A
pp
licatio
ns:
–S
lide
pro
jecto
r
–S
po
tligh
t simu
latio
n
7. Tex
ture M
ap
pin
g
29
Pro
jection
Po
lyg
on
Screen
Eye
Tex
ture
7. Tex
ture M
ap
pin
g
30
Exa
mp
les
7. Tex
ture M
ap
pin
g 31
Mip
-Ma
pp
ing
•M
inim
ized
tex
ture
sp
rod
uce
alia
sing
effe
cts
•S
tore
tex
ture
at m
ultip
le le
vels-o
f-de
tail
•U
se sm
alle
r versio
ns
wh
en
far fro
m ca
me
ra
•M
IPco
me
s from
the
Latin
multum
in parvo,
me
an
ing
am
ultitu
de
in a
sma
ll spa
ce.
with
ou
t mip
ma
pw
ith m
ipm
ap
mip
ma
p
7. Tex
ture M
ap
pin
g 32
Tex
ture In
terpo
latio
n
•C
om
pu
te te
xtu
re va
lue
(R,G,B)
as fu
nctio
n o
f (u,v,z)
•T
ri-line
ar in
terp
ola
tion
u
v
u
v
u
v
zz
7. Tex
ture M
ap
pin
g 33
Co
mp
uta
tion
of th
e Mip
Ma
p
•C
olo
r = w
eig
hte
d a
vera
ge
of n
ea
rby p
ixe
ls (filter)
•S
ee
gluBuild2DMipMaps()
7. Tex
ture M
ap
pin
g 34
Bu
mp
Ma
pp
ing
•A
dd
ing
surfa
ce d
eta
il with
ou
t ad
din
g
ge
om
etry
•P
ertu
rba
tion
of su
rface
no
rma
l
•D
eta
ils inte
ract w
ith lig
ht
•B
um
ps a
re sm
all co
mp
are
d to
ge
om
etry
•B
um
p p
atte
rn is ta
ken
from
a (te
xtu
re-) m
ap
•C
an
also
be
pro
ced
ura
l (fracta
ls)
7. Tex
ture M
ap
pin
g 35
Bu
mp
Ma
pp
ing
•G
iven
a su
rface
p(u,v)
an
d
a p
ertu
rba
tion
valu
e b
(Jim Blinn
)
•P
oin
t p’o
n th
e b
um
py su
rface
•C
om
pu
te n
orm
al a
t Po
int p
’ vu
vu
pp
pp
n×
=∂ ∂
×∂ ∂
=
n np
pb
'+
=
v '
u ''
∂ ∂×
∂ ∂=
pp
n
p
p’
Bu
mp
pa
ttern
b
7. Tex
ture M
ap
pin
g 36
Bu
mp
Ma
pp
ing
•P
artia
l de
rivative
s at p
oin
t p’
•P
ertu
rbe
d n
orm
al a
pp
rox
ima
ted
by (se
e B
linn
)
n np
p)
(b
uu
u '
∂ ∂+
∂ ∂=
∂ ∂
)(
b)
(b
'v
vu
up
np
nn
n×
+×
+=
7. Tex
ture M
ap
pin
g 37
Bu
mp
Ma
pp
ing
•D
iscretiza
tion
usin
g Fin
ite D
iffere
nce
s
v
),v
b(u)
,vb(u
),v
b(u)
,vb(u
b
u
),v
b(u)
,vb(u
),v
b(u)
,vb(u
b
v u
2 2
12
22
11
21
21
22
11
12
−+
−=
−+
−=∆v
∆u
b(u1,v2 )
b(u2,v2 )
b(u2,v1 )
b(u1,v1 )
7. Tex
ture M
ap
pin
g 38
Exa
mp
le: Mu
ltipa
ssB
um
p
7. Tex
ture M
ap
pin
g 39
Furth
er To
pics
•T
ex
ture
Pa
gin
g
•T
ex
ture
Ble
nd
ing
an
d co
mp
ositin
g (R
GB
A)
•M
ultip
le T
ex
ture
s
•D
yna
mic T
ex
ture
s
•B
ill bo
ard
ing
7. Tex
ture M
ap
pin
g
40
Exa
mp
les
Billo
ard
s: Xa
vier D
éco
retet a
l.
Alp
ha
Te
xtu
res