binary shading using geometry and appearance bert buchholz tamy boubekeur doug decarlo marc alexa...
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Binary Shading using Geometry and Appearance
Bert Buchholz Tamy Boubekeur Doug DeCarlo Marc Alexa
Telecom ParisTech – CNRS Rutgers University TU Berlin
Computer Graphics Forum Vol. 29, N. 6, 2010Presented at Eurographics 2011
Binary Drawing
Depicting scenes using 2 colors
Conversion
Binary Rendering
3 D S c e n e
Lighting Reflectance
Geometry
Camera
Related Work
Line Drawing [DeCarlo 2003][Judd 2007]
Image Binarization [Mould and Kaplan 2008]
Local shading operators [Vergne 2008]
Half-Toning [Floyd and Steinberg 1976][Ostromoukhov and Hersch 1995]
Analysis
Variational Rendering Model
Per-pixel decision
Contradictory criteria
Geometry enhancement
Low shading depiction power
VARIATIONAL BINARY RENDERING
Variational Binary Shading
• Deferred shading framework• Rendering data structured as a ST image graph• Edges energies derived from geometry and appearance• Final rendering as a min cut in the image graph
Deferred Shading
Generate a set of arrays (render buffers)– Geometric Properties– Appearance Properties nm
iA 1,0
nmiG
1,0
Rasterization
Ray Tracing
Graph construction
Standard Source-to-Sink Image Graph {V,E}
TiSi
pi eeeE
TSpV i
ImagePixels
Source(white)
Sink(black)
ImageConnectivity
Edges to Source
Edges toSInk
Appearance Contribution to the Graph
• Through terminal weights on • Appearance initiate B/W
segmentation• Experiments using :– Diffuse component– Specular component– Headlight component– Ambient Occlusion/Accessibility
component
TiSi ee
yxWi ,
yxBi ,TerminalWeights
Appearance Graph Terms
Global to local feature control using spatial averages
2
22)(
,
,, ih
vyux
vuii evuAyxA
Support
sizeLocal term: yxAyxAyxA iii ,,,'
Sign:locally lighter or darker
Weighted combination to the global measure.
yxAgyxAgyxB
yxAgyxAgyxW
iiiii
iiiii
,',0max1,1,
,',0max1,,
Global versus Local Thresholding
Global Local
Geometry Contribution to the Graph
• Modelled with neighbor edge weights• Tailors anisotropic, non-local B/W diffusion• Redistributes B/W values to enhance
geometric features• Based on:– View depth values – View dependent curvature, estimated as screen
space normal derivatives [Judd 2007]
pie 1100 ,,, yxyxN
yxz ,
11001100 ,,,,,, 2 yxnyxndyxyxS
Geodesic distance on the Gauss sphereUnit surface normal gathered at 00 , yx
Geometric Term
Local curvature normalization:
2
22
,1100 ,,,,,, c
vyux
vu
evuyxyxyx
Support
size
Yields neighbor edge weights:
2
211001100 ,,,,,,
11001 ,,, k
yxyxyxyx
eyxyxN
Geometry Contribution Modulation
Geometry Contribution Modulation
Small components are successively connected
Graph Minimum Cut
• Max Flow Min Cut Theorem– Shortest split path in the graph→Feature size control through
graph energy• Separate the graph in two components• Boykov and Kolmogorov
implementation [2004]
Cut performance
• Rendering buffers can be speed up using rasterization• Measured on a Core2Duo 1.83GHz (single thread)
RESULTS
Binary Shading
• Global to local features• Appearance & geometry depiction• Large variety of style• Interactive control
Comparison to Line Drawing
Line Drawing Binary Shading
Combination with Line Drawing
Combination with Line Drawing
RGBN Picture Rendering [Toler-Franklin 2007]
Combination with Line Drawing
Comparison to Thresholding
Diffuse Component
Thresholding ThresholdingOver Gaussian Filtering
Binary Rendering
Comparison to Thresholding
Comparison to Image Binarization
(b,e) equivalent to [Mould and Kaplan 2008]
INTERACTIVE CONTROLOn-going work
Interactive Control
• Solution 1: slider-based, for experts– Accurate control– « Too much » control for novice users
• Solution 2: painting interface
Paint Interface
• Supervised sparse B/W contraints• Derive the graph energy structure
Paint Interface
LIMITATIONS AND FUTURE WORK
Animation
… most of straightforward solutions have some temporal coherency failure cases.
Works most of the time but…
K-color Rendering
• Extend to multi-label cuts• Alternative energy minimizer– Lloyd relaxation/k-means– Mean Shift
• k-Component cut• Vector Rendering
CONCLUSION
Binary Shading as a Single Cut
• Global solution• Local to global control• Appearance vs geometry control• High level control
• For automatic binary drawing from 3D Scenes, decals, cut-out, etc…
Thank you
Binary Shading Using Geometry and Appearance.Bert Buchholz, Tamy Boubekeur, Doug DeCarlo and Marc Alexa
Computer Graphics Forum Vol. 29, Nb. 6, 2010Presented at Eurographics 2011