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CS348B Lecture 17 Pat Hanrahan, Spring 2005
Reflection Models
Previous lecture
Phong model
Microfacet models
Gaussian height field on surface
Self-shadowing
Torrance-Sparrow Model
Today
Multiple importance sampling
Anisotropic reflection models
Multiple Importance Sampling
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Multiple Importance Sampling
Reflection of a circular light source by a rough surface
Radius
Sh
inin
ess
Sampling the light source Sampling the BRDF
( ) ( )f x g x dx
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Multiple Importance Sampling
Two sampling techniques
Form weighted combination of samples
The balance heuristic
2, 2
2,2,
2 2,
~ ( )
( )
( )
i
ii
i
X p x
f XY
p X
1, 1
1,1,
1 1,
~ ( )
( )
( )
i
ii
i
X p x
f XY
p X
1 1, 2 2,i i iY wY w Y
1 1 2 21 2
( )( ) ( ) ( ) ( ) ( ) ( )
( ) ( )i
i
p xw x p x w x p x w x p x
p x p x
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Multiple Importance Sampling
Source: Veach and Guibas
Anisotropic Reflection Model
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Anisotropic Reflection
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Quarterhorse
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Reflection from a Cylinder
T
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Reflection from a Cylinder
T
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Reflection from a Cylinder
T
L
ˆˆ( )
NR L
N
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Reflection from a Cylinder
T
L
ˆˆ( )
NR L
N
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Reflection from a Cylinder
T
L
ˆˆ( )
NR L
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Anisotropic Reflection
CS348B Lecture 17 Pat Hanrahan, Spring 2005
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 2005
Shape of Anisotropic Highlights
From Lu, Koenderink, Kappers
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Kajiya-Kay Model
Diffuse
Specular
2ˆ ˆsin 1L T L
cos cos cos sin sinss
E L E L E L
L
E
T
ˆˆ( )
NR L
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Herbert
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Fiber Model
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Fiber Model
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Fiber Model
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Caustics
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Hair Appearance
CS348B Lecture 17 Pat Hanrahan, Spring 2005
Hair Appearance
CS348B Lecture 17 Pat Hanrahan, Spring 2005
CS348B Lecture 17 Pat Hanrahan, Spring 2005
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