Transcript Jiaping Wang1 Peiran Ren1,3 Minmin Gong1 John Snyder2 Baining Guo1,3 1 Microsoft Research Asia 2 Microsoft Research 3 Tsinghua University.

Jiaping Wang1 Peiran Ren1,3 Minmin Gong1
John Snyder2
Baining Guo1,3
1 Microsoft
Research Asia
2 Microsoft
Research
3 Tsinghua
University
Complex, detailed reflectance
Spatial/temporal variation
 All BRDF types:

 parametric ↔ measured
 isotropic ↔ anisotropic
 glossy ↔ mirror-like
Previous work
Spatial
Variation
SVBRDF
single
BRDF
static
dynamic
Temporal
Variation
Previous work
Spatial
Variation
[Ng03]
[Wang04]
[Liu04]
[Wang06]
[Tsai06]
[Krivanek08]
SVBRDF
single
BRDF
[Wang04]
static
dynamic
Temporal
Variation
Previous work
Spatial
Variation
[Green06]
[Green07]
SVBRDF
[Green06]
single
BRDF
[Wang04]
static
dynamic
Temporal
Variation
Previous work
Spatial
Variation
[Ben-Artzi06]
[Sun07]
[Ben-Artzi08]
SVBRDF
[Green06]
single
BRDF
[Wang04]
[Ben-Artzi06]
static
dynamic
Temporal
Variation
Previous work
Spatial
Variation
Our method:
- per-pixel SVBRDF
- dynamic SVBRDF
- all BRDF types
- all-frequency
SVBRDF
[Green06]
[Wang09]
[Wang04]
[Ben-Artzi06]
single
BRDF
static
dynamic
Temporal
Variation
Rendering Equation
2D lighting
 4D visibility
 6D reflectance (SVBRDF)

light
SVBRDF
o
n
x
visibility
i
cosine
Precomputed Radiance Transfer

Dot product
[Sloan et al. 2002]
light
light transfer
Precomputed Radiance Transfer

Dot product
light
light transfer
[Sloan et al. 2002]

Triple product
light
visibility
BRDF × cosine
[Ng et al. 2004]
Light Transport & Precomputed
Precomputed Radiance Transfer

Dot product
light
light transfer
[Sloan et al. 2002]

Triple product
light
visibility
light
visibility
BRDF × cosine
[Ng et al. 2004]

Ours method
BRDF
cosine
LT & P
LT & P
Precomputed Radiance Transfer

Dot product
light
light transfer
[Sloan et al. 2002]

Triple product
BRDF × cosine
light
visibility
light
visibility
BRDF
cosine
LT & P
LT & P
LT & P
[Ng et al. 2004]

Ours method
Algorithm Overview
o
Spherical Gaussians
Spherical Gaussians
Algorithm Overview
o
Spherical Gaussians
SSDF
Environment
Dynamic, spatial varying BRDF
Outline

Reflectance Representation
 Microfacet Model with SGs

Visibility Representation
 Signed Spherical Distance Function

Lighting & Rendering
o
Outline

Reflectance Representation
 Microfacet Model with SGs

Visibility Representation
 Signed Spherical Distance Function

Lighting & Rendering
o
Spherical Gaussian (SG)
center
intensity
sharpness
 trivial rotation
 all-frequency signals
Spherical Gaussian (SG)
center
intensity
sharpness
 trivial rotation
 all-frequency signals
inner product:
vector product:
SG Mixtures
Sum of Multiple SGs:
Original
SG, N = 7
SG, N = 3
SG, N = 1
Microfacet BRDF Model

surface modeled by tiny mirror facets
[Cook 82]
Microfacet BRDF Model

surface modeled by tiny mirror facets
[Cook 82]
normal distribution
Represented by SG
shadow term
fresnel term
Parametric Models
 single-lobe, analytic approximation
 Cook-Torrance [Cook et al. 1981]
 Ward [Ward 1992]
 Blinn-Phong [Blinn 1977]
Parametric BRDFs
7-lobe SGM ground truth
Anisotropic Parametric Models
nu=8, nv=128
nu=25, nv=400
nu=75, nv=1200
Measured BRDFs
BRDF from [Matusik03]
svBRDF from [Wang08] & [Lawance06]
Representation Efficiency
 Parametric
BRDF
Texturing of original BRDF parameters
isotropic : 7 float/texel: diffuse, specular, shininess
Anisotropic: 8 float/texel: diffuse, specular, shininess u/v
 Measured
BRDF
number
of SGs
Floats
per SG
floats per
texel
isotropic
1-3
4
4~12 + 3
anisotropic
2-7
6
12~42 + 3
Texturing of SGs
BRDF Slices
o
Normal Distribution
in Half-vector Domain
BRDF Slice
in light-vector
Half-vector Domain
SG Warping
SG not closed under -1
 approx. by per-SG warp of D*

SG Warping
SG not closed under -1
 approx. by per-SG warp of D*

Parametric svBRDF Painting
Outline

Reflectance Representation
 Microfacet Model with SGs

Visibility Representation
 Signed Spherical Distance Function

Lighting & Rendering
o
Visibility at one point
scene
x
binary visibility function
V(x,i)
Visibility Prerequisite

Preserve sharp visibility boundary

inner product for Diffuse Term
SGs

?
vector product for Specular Term
SGs
?
Spherical Signed Distance Function
i0
i1
binary visibility, V(i)
Vd(i0)
Vd(i1)
SSDF, Vd (i)
SSDF-SG Product
SSDF
Visibility
SSDF-SG Product
p
SSDF
p
Visibility
≈
p
Approx. Visibility for p
p
p
SG centered at p
Approx. Visibility for p
SSDF-SG Product
p
SSDF
≈
p
Visibility
p
Approx. Visibility for p
=0.329
p
SG centered at p
Inner product
vector product
Per-pixel Shading & Shadowing
Outline

Reflectance Representation
 Microfacet Model with SGs

Visibility Representation
 Signed Spherical Distance Function

Lighting & Rendering
o
Local Light Source

Point light

directional light
Environment Light
for diffuse shading
for specular shading
SGs (10 lobes)
prefiltered MIPMAP
[Tsai and Shih 2006]
[Kautz et al. 2000]
Environment Light
for diffuse shading
for specular shading
SGs (10 lobes)
prefiltered MIPMAP
[Tsai and Shih 2006]
[Kautz et al. 2000]
Environment + Local Lighting
Rendering Summary: Diffuse
Microfacet Model
Environment Light
Rendering Summary: Diffuse
Microfacet Model
Environment Light
●
BRDF Slice
in SGs
Cosine Term
in SGs
Environment
in SGs
Visibility
in SSDF
Rendering Summary: Specular
Microfacet Model
Environment Light
●
BRDF Slice
in SGs
Cosine Term
in SGs
Visibility
in SSDF
Prefiltered
Environment
Performance Summary
Scene
BRDF Type
svBRDF
Resolusion
svBRDF
Size
Env.
FPS
Pt.
FPS
1024×1024
7.2MB
171
250
Teapot
CT (iso. 1 SG)
Dragon
Ward (iso. 1 SG)
512×512
1.8MB
165
231
DishBall
AS (aniso. 7 SGs)
512×1024
4.1MB
55
30
card(iso. 2 SGs)
512×512
4.2MB
satin(aniso. 5 SGs)
850×850
22.4MB
48
35
velvet (aniso. 2SGs)
850×850
9.4MB
168
145
DishCard

Testing Machine
 Intel Core2 Duo 3.2G CPU, 4GB memory
 nVidia Geforce 8800 Ultra graphics card
Performance Summary
Scene
BRDF Type
svBRDF
Resolusion
svBRDF
Size
Env.
FPS
Pt.
FPS
1024×1024
7.2MB
171
250
Teapot
CT (iso. 1 SG)
Dragon
Ward (iso. 1 SG)
512×512
1.8MB
165
231
DishBall
AS (aniso. 7 SGs)
512×1024
4.1MB
55
30
card(iso. 2 SGs)
512×512
4.2MB
satin(aniso. 5 SGs)
850×850
22.4MB
48
35
velvet (aniso. 2SGs)
850×850
9.4MB
168
145
DishCard

Testing Machine
 Intel Core2 Duo 3.2G CPU, 4GB memory
 nVidia Geforce 8800 Ultra graphics card
All-Frequency Visual Effects
bump maps
dynamic
BRDFs
anisotropic
BRDFs
measured
BRDFs
Reflectance Painting
parametric BRDFs
measured SVBRDFs
Conclusion

Overall method:
 glossy to mirror-like, detailed, dynamic reflectance
 all-frequency shadows
 real-time per-pixel shading

SG mixtures for microfacet-based reflectance
 compact yet accurate
 fast rotation, warping, products

SSDFs for visibility
 fast products with SG mixtures
 non-ghosting spatial interpolation
Conclusion

Overall method:
 glossy to mirror-like, detailed, dynamic reflectance
 all-frequency shadows
 real-time per-pixel shading

SG mixtures for microfacet-based reflectance
 compact yet accurate
 fast rotation, warping, products

SSDFs for visibility
 fast products with SG mixtures
 non-ghosting spatial interpolation
Future work
 dynamic visibility
 inter-reflection
 anisotropic spherical Gaussian
 SSDF compression
 simpler SVBRDF acquisition
Future work
 dynamic visibility
 inter-reflection
 anisotropic spherical Gaussian
 SSDF compression
 simpler SVBRDF acquisition
Thank you for your attention.
Visibility Cuts [Cheslack-Postava et al.2008]

Light-cut framework
 No highly glossy reflectance
 Highly tessellation
 Not real-time
SG Scaling
 Shadowing and Fresnel terms
 Assume low-frequency [Ashkmin01, Ngan05]
 approx. by per-SG scale
SSDF Compression
PCA:
binary visibility
SSDF
compressed SSDF
Error sources
BRDF fitting error
 diffuse light fitting error
 SG warping error
 SSDF-SG product error
 SSDF compression error

SSDF-SG product error
 visibility function is approximate
 product is approximate
 inner product error typically less than 2%
 vector product error larger, but not visually
significant
 error decreases as λ increases
SG mixtures
N-lobe approximation
original
SG, N = 3
L2 = 6.2%
SG, N = 2
L2 = 8.2%
violet-acrylic NDF [Ngan et al. 2005]
SG, N = 1
L2 = 25%
SG representation of lighting

distant light → environment map (EM)
 diffuse shading:
○ fit EM with SG mixture (10 lobes) [Tsai and Shih 2006]
 specular shading:
○ prefilter EM with SGs of various λ [Kautz et al. 2000]
EM Prefiltering with SGs
λ=21000,
level 1
λ =329,
level 4
…
 MIPMAP of prefiltered cubemaps
 λ reduced by 1/4 per level
λ =5.1,
level 7
…