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CS348B Lecture 17 Pat Hanrahan, Spring 2006
Reflection Models
Previous lectures
Ideal materials: mirrors, glass, matte
Glossy materials
Today
Anisotropic reflection
Subsurface reflection; translucent materials
Anisotropic Reflection
Model
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
Anisotropic Reflection
CS348B Lecture 17 Pat Hanrahan, Spring 2006
Quarterhorse
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
Reflection from a Cylinder
T
L
ˆˆ( )
NR L
CS348B Lecture 17 Pat Hanrahan, Spring 2006
Anisotropic Reflection
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
Shape of Anisotropic Highlights
From Lu, Koenderink, Kappers
Fibers tangent to the plane defined by the halfway vector reflect light
CS348B Lecture 17 Pat Hanrahan, Spring 2006
Shape of Anisotropic Highlights
From Lu, Koenderink, Kappers
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
Kajiya-Kay Model
Diffuse
Specular
( )2ˆ ˆsin 1Lθ = − •T L
( ) ( )cos cos cos sin sinss
E L E L E Lθ θ θ θ θ θ− = +
L
E
T
ˆˆ( )
NR L
CS348B Lecture 17 Pat Hanrahan, Spring 2006
Herbert
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
Previous Work
Measurements for cosmetics industry
[Stamm 1977; Bustard & Smith 1994]
Structure of fiber surface
[Robbins ’94]
CS348B Lecture 17 Pat Hanrahan, Spring 2006
Fiber Model
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
Fiber Model
CS348B Lecture 17 Pat Hanrahan, Spring 2006
Fiber Model
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
Caustics
CS348B Lecture 17 Pat Hanrahan, Spring 2006
Hair Appearance
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
Hair Appearance
CS348B Lecture 17 Pat Hanrahan, Spring 2006
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Subsurface Reflection
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
Traditional Reflection Models: BRDF
BRDF:( , )( , , )( , )
r or i o
i i
dL xf xdE x
ωω ωω
≡
CS348B Lecture 17 Pat Hanrahan, Spring 2006
Subsurface Scattering: BSSRDF
BSSRDF:( , )( , ; , )( , )
r o oi i o o
i i i
dL xS x xd x
ωω ωω
≡Φ
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
Translucent Materials: Jade
CS348B Lecture 17 Pat Hanrahan, Spring 2006
Translucent Materials: Marble
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
Translucent Materials: Skin
CS348B Lecture 17 Pat Hanrahan, Spring 2006
Translucent Materials: Leaves
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
How?
BSSRDF:
CS348B Lecture 17 Pat Hanrahan, Spring 2006
Highly Scattering Media
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
Highly Scattering Media
CS348B Lecture 17 Pat Hanrahan, Spring 2006
Diffusion Approximation
( )krer
rφ
−
= Φ
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
Dipole Diffusion Approximation
1 2( ( ) ( ))( )di
r rR r φ φ• ∇ −∇= −
ΦN
CS348B Lecture 17 Pat Hanrahan, Spring 2006
Single Scattering
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
Evaluating the BSSRDF
Diffusion approximation( , ) ( , ; , ) ( , ) cosr o o i i o o i i i i iA
L x S x x L x d dAω ω ω ω θ ωΩ
= ∫ ∫
CS348B Lecture 17 Pat Hanrahan, Spring 2006
Marble: BDRF versus BSSDRF
BRDF BSSRDFBRDF BSSRDF
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
Marble: MCRT vs BSSRDF
MCRT BSSRDFMCRT BSSRDF
CS348B Lecture 17 Pat Hanrahan, Spring 2006
Skim Milk
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
Whole Milk
CS348B Lecture 17 Pat Hanrahan, Spring 2006
Diffuse Milk
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CS348B Lecture 17 Pat Hanrahan, Spring 2006
A Face (BSSRDF Model)
Modeled by Stephen Stahlberg
CS348B Lecture 17 Pat Hanrahan, Spring 2006
A Face (BRDF Approximation)
Modeled by Stephen Stahlberg
