Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike...
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Transcript of Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike...
![Page 1: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/1.jpg)
Lightcuts: A Scalable Approach to Illumination
Lightcuts: A Scalable Approach to Illumination
Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian,
Kavita Bala, Donald Greenberg
Program of Computer Graphics, Cornell University
![Page 2: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/2.jpg)
LIGHTCUTS
SIGGRAPH 2005
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Lightcuts Lightcuts
• Efficient, accurate complex illumination
Environment map lighting & indirectTime 111s
Textured area lights & indirectTime 98s
(640x480, Anti-aliased, Glossy materials)
![Page 3: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/3.jpg)
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ScalableScalable
• Scalable solution for many point lights
– Thousands to millions
– Sub-linear cost
0
100
200
300
400
500
600
0 1000 2000 3000 4000
Number of Point Lights
Tim
e (s
ecs)
Standard
Ward
Lightcut
Tableau Scene
![Page 4: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/4.jpg)
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Complex LightingComplex Lighting
• Simulate complex illumination using point lights
– Area lights
– HDR environment maps
– Sun & sky light
– Indirect illumination
• Unifies illumination
– Enables tradeoffs between components
Area lights + Sun/sky + Indirect
![Page 5: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/5.jpg)
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Related WorkRelated Work• Hierarchical techniques
– Hierarchical radiosity [eg, Hanrahan et al. 91, Smits et al. 94]
– Light hierarchy [Paquette et al. 98]
• Many lights
– [eg, Teller & Hanrahan 93, Ward 94, Shirley et al. 96, Fernandez et al. 2002, Wald et al. 2003]
• Illumination coherence
– [eg, Kok & Jensen 92, Ward 92, Scheel et al. 2002, Krivanek et al. 2005]
• Env map illumination
– [Debevec 98, Agarwal et al. 2003, Kollig & Keller 2003, Ostromoukhov et al. 2004]
• Instant Radiosity
– [Keller 97, Wald et al. 2002]
![Page 6: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/6.jpg)
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Talk OverviewTalk Overview
• Lightcuts
– Scalable accurate solution for complex illumination
• Reconstruction cuts
– Builds on lightcuts
– Use smart interpolation to further reduce cost
![Page 7: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/7.jpg)
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Lightcuts ProblemLightcuts Problem
Visiblesurface
![Page 8: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/8.jpg)
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Lightcuts ProblemLightcuts Problem
![Page 9: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/9.jpg)
LIGHTCUTS
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Lightcuts ProblemLightcuts Problem
Camera
![Page 10: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/10.jpg)
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Key ConceptsKey Concepts
• Light Cluster
– Approximate many lights by a single brighter light (the representative light)
![Page 11: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/11.jpg)
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Key ConceptsKey Concepts
• Light Cluster
• Light Tree
– Binary tree of lights and clusters
Clusters
IndividualLights
![Page 12: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/12.jpg)
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Key ConceptsKey Concepts
• Light Cluster
• Light Tree
• A Cut
– A set of nodes that partitions the lights into clusters
![Page 13: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/13.jpg)
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Simple ExampleSimple Example
#1 #2 #3 #4
1 2 3 4
1 4
Light Tree
Clusters
IndividualLights
RepresentativeLight
4
![Page 14: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/14.jpg)
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Three Example CutsThree Example Cuts
1 2 3 4
1 4
4
1 2 3 4
1 4
4
1 2 3 4
1 4
4
Three Cuts
#1 #2 #4 #1 #3 #4 #1 #4
![Page 15: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/15.jpg)
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Three Example CutsThree Example Cuts
1 2 3 4
1 4
4
1 2 3 4
1 4
4
1 2 3 4
1 4
4
Three Cuts
#1 #2 #4 #1 #3 #4 #1 #4
Good Bad Bad
![Page 16: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/16.jpg)
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Three Example CutsThree Example Cuts
1 2 3 4
1 4
4
1 2 3 4
1 4
4
1 2 3 4
1 4
4
Three Cuts
#1 #2 #4 #1 #3 #4 #1 #4
Bad Good Bad
![Page 17: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/17.jpg)
LIGHTCUTS
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Three Example CutsThree Example Cuts
1 2 3 4
1 4
4
1 2 3 4
1 4
4
1 2 3 4
1 4
4
Three Cuts
#1 #2 #4 #1 #3 #4 #1 #4
Good Good Good
![Page 18: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/18.jpg)
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Algorithm OverviewAlgorithm Overview
• Pre-process
– Convert illumination to point lights
– Build light tree
• For each eye ray
– Choose a cut to approximate the illumination
![Page 19: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/19.jpg)
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Convert IlluminationConvert Illumination
• HDR environment map
– Apply captured light to scene
– Convert to directional point lightsusing [Agarwal et al. 2003]
• Indirect Illumination
– Convert indirect to direct illuminationusing Instant Radiosity [Keller 97]
• Caveats: no caustics, clamping, etc.
– More lights = more indirect detail
![Page 20: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/20.jpg)
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Algorithm OverviewAlgorithm Overview
• Pre-process
– Convert illumination to point lights
– Build light tree
• For each eye ray
– Choose a cut to approximate the local illumination
• Cost vs. accuracy
• Avoid visible transition artifacts
![Page 21: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/21.jpg)
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Perceptual MetricPerceptual Metric
• Weber’s Law
– Contrast visibility threshold is fixed percentage of signal
– Used 2% in our results
• Ensure each cluster’s error < visibility threshold
– Transitions will not be visible
– Used to select cut
![Page 22: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/22.jpg)
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Illumination EquationIllumination Equation
Material term
result = Mi Gi Vi Iilights
Geometric term
Visibility term
Light intensity
Currently support diffuse, phong, and Ward
![Page 23: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/23.jpg)
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Illumination EquationIllumination Equation
Material term
result = Mi Gi Vi Iilights
Geometric term
Visibility term
Light intensity
![Page 24: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/24.jpg)
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Illumination EquationIllumination Equation
Material term
result = Mi Gi Vi Iilights
Geometric term
Visibility term
Light intensity
![Page 25: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/25.jpg)
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Cluster ApproximationCluster Approximation
Cluster
result ~ Mj Gj Vj Iilights
~
j is the representative light
![Page 26: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/26.jpg)
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error Mub Gub Vub Ii
Cluster Error BoundCluster Error Bound
Cluster
lights
• Bound each term
– Visibility <= 1 (trivial)
– Intensity is known
– Bound material and geometric terms using cluster bounding volume
ub == upper bound
![Page 27: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/27.jpg)
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Cut Selection AlgorithmCut Selection Algorithm
Cut
• Start with coarse cut (eg, root node)
![Page 28: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/28.jpg)
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Cut Selection AlgorithmCut Selection Algorithm
Cut
• Select cluster with largest error bound
![Page 29: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/29.jpg)
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Cut Selection AlgorithmCut Selection Algorithm
Cut
• Refine if error bound > 2% of total
![Page 30: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/30.jpg)
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Cut Selection AlgorithmCut Selection Algorithm
Cut
![Page 31: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/31.jpg)
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Cut Selection AlgorithmCut Selection Algorithm
Cut
![Page 32: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/32.jpg)
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Cut Selection AlgorithmCut Selection Algorithm
Cut
![Page 33: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/33.jpg)
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Cut Selection AlgorithmCut Selection Algorithm
Cut
• Repeat until cut obeys 2% threshold
![Page 34: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/34.jpg)
Lightcuts (128s) Reference (1096s)
Kitchen, 388K polygons, 4608 lights (72 area sources)
![Page 35: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/35.jpg)
Lightcuts (128s) Reference (1096s)
Error Error x16
Kitchen, 388K polygons, 4608 lights (72 area sources)
![Page 36: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/36.jpg)
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Combined IlluminationCombined Illumination
Lightcuts 128s
4 608 Lights(Area lights only)
Lightcuts 290s
59 672 Lights(Area + Sun/sky + Indirect)
![Page 37: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/37.jpg)
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Combined IlluminationCombined Illumination
Lightcuts 128s
4 608 Lights(Area lights only)
Avg. 259 shadow rays / pixel
Lightcuts 290s
59 672 Lights(Area + Sun/sky + Indirect)
Avg. 478 shadow rays / pixel(only 54 to area lights)
![Page 38: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/38.jpg)
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Lightcuts RecapLightcuts Recap
• Unified illumination handling
• Scalable solution for many lights
– Locally adaptive representation (the cut)
• Analytic cluster error bounds
– Most important lights always sampled
• Perceptual visibility metric
Lightcuts implementation sketch, Petree Hall C, ~4:30pm
![Page 39: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/39.jpg)
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Talk OverviewTalk Overview
• Lightcuts
– Scalable accurate solution for complex illumination
• Reconstruction cuts
– Builds on lightcuts
– Use smart interpolation to further reduce cost
![Page 40: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/40.jpg)
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Reconstruction CutsReconstruction Cuts
• Subdivide image into blocks
– Generate samples at corners
• Within blocks
– Interpolate smooth illumination
– Use shadow rays when needed to preserve features
• Shadow boundaries, glossy highlights, etc.
• Anti-aliasing
– (5-50 samples per pixel)
![Page 41: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/41.jpg)
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Image SubdivisionImage Subdivision
• Divide into max block size (4x4 blocks)
4x4 block
![Page 42: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/42.jpg)
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Image SubdivisionImage Subdivision
• Divide into max block size (4x4 blocks)
• Trace multiple eye rays per pixel
• Subdivide blocks if needed
– Based on material, surface normal,and local shadowing configuration
![Page 43: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/43.jpg)
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Image SubdivisionImage Subdivision
• Divide into max block size (4x4 blocks)
• Trace multiple eye rays per pixel
• Subdivide blocks if needed
– Based on material, surface normal,and local shadowing configuration
• Compute samples at corners
Samples
![Page 44: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/44.jpg)
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Image SubdivisionImage Subdivision
• Divide into max block size (4x4 blocks)
• Trace multiple eye rays per pixel
• Subdivide blocks if needed
– Based on material, surface normal,and local shadowing configuration
• Compute samples at corners
• Shade eye rays using reconstruction cuts
Samples Reconstructioncut
![Page 45: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/45.jpg)
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Sample ConstructionSample Construction
• Compute a lightcut at each sample
• For each node on or above the cut
– Create impostor light (directional light)
– Reproduce cluster’s effect at sample
Cluster
ImpostorDirectional light
![Page 46: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/46.jpg)
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Reconstruction CutReconstruction Cut
• Top-down traversal of light tree
– Comparing impostors from nearby samples
Not visited
Recurse
Occluded
Interpolate
Shadow ray
![Page 47: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/47.jpg)
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Reconstruction CutReconstruction Cut
• Recurse if samples differ significantly
Not visited
Recurse
Occluded
Interpolate
Shadow ray
![Page 48: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/48.jpg)
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Reconstruction CutReconstruction Cut
• Discard if cluster occluded at all samples
Not visited
Recurse
Occluded
Interpolate
Shadow ray
![Page 49: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/49.jpg)
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Reconstruction CutReconstruction Cut
Not visited
Recurse
Occluded
Interpolate
Shadow ray
![Page 50: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/50.jpg)
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Reconstruction CutReconstruction Cut
Not visited
Recurse
Occluded
Interpolate
Shadow ray
![Page 51: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/51.jpg)
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Reconstruction CutReconstruction Cut
• Interpolate if sample impostors are similar
Not visited
Recurse
Occluded
Interpolate
Shadow ray
![Page 52: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/52.jpg)
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Reconstruction CutReconstruction Cut
• If cluster contribution small enough, shoot shadow ray to representative light
– Lightcut-style evaluation
Not visited
Recurse
Occluded
Interpolate
Shadow ray
![Page 53: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/53.jpg)
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Reconstruction CutReconstruction Cut
Not visited
Recurse
Occluded
Interpolate
Shadow ray
![Page 54: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/54.jpg)
Temple, 2.1M polygons, 505 064 lights, (Sun/sky+Indirect)
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Temple, reconstruction cut block size
![Page 56: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/56.jpg)
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Result StatisticsResult Statistics
• Temple model (2.1M polys, 505 064 lights)
Image algorithmAvg. eye rays
per pixelImage time
Lightcuts only 1 225s
Combined (anti-aliased) 5.5 189s
Cut type Avg. shadow rays per cut
Lightcut 373
Reconstruction cut 9.4
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Grand Central, 1.46M polygons, 143 464 lights, (Area+Sun/sky+Indirect)
Avg. shadow rays per eye ray 46 (0.03%)
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Tableau, 630K polygons, 13 000 lights, (EnvMap+Indirect)
Avg. shadow rays per eye ray 17 (0.13%)
![Page 59: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/59.jpg)
Bigscreen, 628K polygons, 639 528 lights, (Area+Indirect)
Avg. shadow rays per eye ray 17 (0.003%)
![Page 60: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/60.jpg)
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ConclusionsConclusions
• Lightcuts
– Scalable, unified framework for complex illumination
– Analytic cluster error bounds & perceptual visibility metric
• Reconstruction cuts
– Exploits coherence
– High-resolution, anti-aliased images
0
100
200
300
400
500
600
0 1000 2000 3000 4000
Number of Point Lights
Tim
e (s
ecs)
Standard
Ward
Lightcut
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Future WorkFuture Work
• Visibility bounds
• More light types
– Spot lights etc.
• More BRDF types
– Need cheap tight bounds
• Other illumination types
– Eg, caustics
![Page 62: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/62.jpg)
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AcknowledgementsAcknowledgements
• National Science Foundation grant ACI-0205438
• Intel corporation for support and equipment
• The modelers– Kitchen: Jeremiah Fairbanks
– Bigscreen: Will Stokes
– Grand Central: Moreno Piccolotto, Yasemin Kologlu, Anne Briggs, Dana Gettman
– Temple: Veronica Sundstedt, Patrick Ledda, and the graphics group at University of Bristol
– Stanford and Georgia Tech for Buddha and Horse geometry
![Page 63: Lightcuts: A Scalable Approach to Illumination Bruce Walter, Sebastian Fernandez, Adam Arbree, Mike Donikian, Kavita Bala, Donald Greenberg Program of.](https://reader036.fdocuments.in/reader036/viewer/2022062714/56649d4b5503460f94a29100/html5/thumbnails/63.jpg)
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The EndThe End
• Questions?
Lightcuts implementation sketch, Petree Hall C, ~4:30pm
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ScalableScalable
• Scalable solution for many point lights
– Thousands to millions
– Sub-linear cost
0
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400
500
600
0 1000 2000 3000 4000 5000
Number of Point Lights
Tim
e (s
ecs)
Standard
Ward
Lightcuts
0
100
200
300
400
500
600
0 1000 2000 3000 4000
Number of Point Lights
Tim
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Standard
Ward
Lightcut
Tableau Scene Kitchen Scene
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Lightcuts Reference
Error x 16Cut size
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Kitchen, 388K polygons, 59,672 Lights
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Kitchen, shadow ray false color
0 750 1500
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Tableau, shadow ray false color
0 750 1500
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Kitchen with sample locations marked
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Types of Point LightsTypes of Point Lights
• Omni
– Spherical lights
• Oriented
– Area lights, indirect lights
• Directional
– HDR env maps, sun&sky