announcements final project presentations on wednesday each group has 10 minutes place.ppt talk in...
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AnnouncementsFinal project presentations on Wednesday
• Each group has 10 minutes• Place .ppt talk in artifact directory
Final reports due on Friday at 11:59pm• Web page (see project4 web page)• Does not have to be long, but should be sufficient to
describe what you did, related work, results, and discussion
Evals at the end of class today
Matting and Transparency
Slides adapted from Alexei Efros, Yung-Yu Chuang, and Shree Nayar
How does Superman fly?
Super-human powers?
OR
Image Matting?
Digital matting
Forrest Gump (1994)
Compositing
BFC )α(α 1
F B
C
foreground color alpha matte background plate
composite
compositingequationB
F
C
=0
Compositing
BFC )α(α 1
F B
Ccomposite
compositingequationB
F
C=1
Compositing
BFC )α(α 1
F B
Ccomposite
compositingequationB
FC
=0.6
Matting
CobservationBFC )α(α 1
compositingequation
F B
Matting
CBFC )α(α 1
compositingequation
F B
Three approaches:
1 reduce #unknowns
2 add observations
3 add priors
Matting (reduce #unknowns)
C
F BB
BFC )α(α 1
differencematting
Matting (reduce #unknowns)
C
F
BFC )α(α 1B
blue screenmatting
Problems with color difference
Background color is usually not perfect! (lighting, shadowing…)
Matting (add observations)
F
BFC )α(α 1
Smith & Blinn, 96
BFC )α(α 1
BC
Natural image matting
BC
Matting (add priors)
F
BFC )α(α 1
B
rotoscopingRuzon-Tomasi
FG
BG
unknown
inputtrimapalpha
input composite
Environment Matting and Compositing
Video
Douglas E. Zongker ~ Dawn M. Werner ~ Brian Curless ~ David H. Salesin
Fast Separation of Direct and Global
Images
Using High Frequency IlluminationShree K. Nayar
Gurunandan G. Krishnan
Columbia University
SIGGRAPH ConferenceBoston, July 2006
Support: ONR, NSF, MERL
Michael D. Grossberg
City College of New York
Ramesh Raskar
MERL
source
surface
P
Direct and Global Illumination
A
A : Direct
B
B : Interrelection
C
C : Subsurface
D
participating medium
D : Volumetric translucent surface
E
E : Diffusion
camera
],[],[],[ icLicLicL gd
direct globalradiance
Direct and Global Components: Interreflections
surface
i
camera
source
P
g jiLjiAicL ],[],[],[
j
BRDF and geometry
High Frequency Illumination Pattern
surface
camera
source
fraction of activated source elements
],[],[],[ icLicLicL gd +
i
High Frequency Illumination Pattern
surface
fraction of activated source elements
camera
source
],[],[],[ icLicLicL gd + - ],[],[ icLicL g )1(
i
:2
1 min2LLg
Separation from Two Images
direct global
,minmax LLLd
Other Global Effects: Subsurface Scattering
translucent surface
camera
source
i
j
Other Global Effects: Volumetric Scattering
surface
camera
source
participating medium
i
j
Diffuse Interreflections
SpecularInterreflections
Volumetric Scattering Subsurface
Scattering
Diffusion
Scene
Scene
Direct Global
Real World Examples:
Can You Guess the Images?
Eggs: Diffuse Interreflections
Direct Global
Wooden Blocks: Specular Interreflections
Direct Global
Kitchen Sink: Volumetric Scattering
Volumetric Scattering:
Chandrasekar 50, Ishimaru 78
Direct Global
Peppers: Subsurface Scattering
Direct Global
Hand
Direct Global
Skin: Hanrahan and Krueger
93,
Uchida 96, Haro 01, Jensen et
al. 01,
Cula and Dana 02, Igarashi et
al. 05, Weyrich et al. 05
Face: Without and With Makeup
GlobalDirect
GlobalDirectWithout Makeup
With Makeup
Blonde Hair
Hair Scattering: Stamm et al. 77,
Bustard and Smith 91, Lu et al. 00
Marschner et al. 03
Direct Global
www.cs.columbia.edu/CAVE