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Terrain SynthesisTerrain Synthesisby Digital Elevation Modelsby Digital Elevation Models
Howard Zhou, Jie Sun, Greg Turk, and James M. Rehg
2006.10.05
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Table of ContentsTable of Contents
1. Introduction2. Feature extraction3. Feature matching and alignment4. Patch stitching5. Conclusion
IntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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Why?Why?
Numerous applications Landscape design Flight simulators Feature film special effects Computer games
IntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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Terrain synthesisFractal model
fBm - fractional Brownian motion (Mandelbrot 1982) Midpoint displacement, recursive subdivision …(Fournier
1982, Miller 1986, Voss 1985, Lewis 1987, Szeliski, et al. 1989)
Erosion model Physical erosion simulation (Kelley, et al. 1988)
Combination of Both Fractal terrains with erosion features (Musgrave et al.
1989) Most commercial landscaping software such as Terragen,
Bryce, Vue d’seprit, and Mojoworld, etc.
Previous WorkPrevious WorkIntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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Limitation of previous terrain synthesis approaches Limited control by user
(parameter tuning) Hard to capture real terrain style
Previous WorkPrevious WorkIntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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What If ?What If ?IntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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Patch based texture synthesis Image quilting (Efros and Freeman 2001), Graphcut
(Kwatra et al. 2003)
Feature guided texture synthesis Image analogy (Hertzmann et al. 2000), Feature
matching and deformation (Zhang et al. 2003, Wu and Yu 2004)
Related WorkRelated WorkIntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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Terrain synthesis is not simply texture synthesis on height fields. Terrain synthesis must preserve global features such as
ridges and valleys. Terrain synthesis must be globally controllable. Unlike general textures, terrain doesn’t have natural
boundaries.
Terrain synthesis is not Terrain synthesis is not texture synthesistexture synthesis
IntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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First example-based terrain synthesisUser control via feature sketches.Feature-based approach to matching and
placement of large curvilinear terrain features.Tree-ordered patch placement algorithm.Multiple terrain style.
Our ContributionOur ContributionIntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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Feature Extraction Extract important terrain features (valleys, ridges, …)
Feature matching and deformation Match terrain features between user sketch and terrain
data to find candidate patch Use deformation to align features
Patch stitching Use graph cuts and Poisson interpolation to remove
visible seams between neighboring patches
ProcedureProcedureIntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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FlowchartFlowchart
Feature extraction
Matching and deformation
Patch stitching
IntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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Finding ridges and valleys Branches and Ends Path Features
Chang’s PPA algorithm (Profile recognition and polygon breaking)
Branch
End
Path
Feature Feature ExtractionExtraction
IntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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Why PPA?Why PPA?
Grand Canyon (shaded relief)
Edge detection result
PPA result
IntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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TargetConnection
Profile Recognition
PolygonBreaking
BranchReduction
PPA explainedPPA explainedIntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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Input
In actionIn action
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Profile Recognition
In actionIn action
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Polygon building
In actionIn action
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Polygon Breaking
In actionIn action
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Branch Reduction
In actionIn action
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Result
In actionIn action
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Feature Feature placement (tree placement (tree traversal)traversal)
IntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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Why is order Why is order important?important?
Raster-scan patch placement (ncc)
Tree traversal
IntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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Most of the time, the feature patches need alignment before they can be used.
Thin plate spline mapping for feature deformation Two sets of corresponding feature points from feature
matching Small deformation in terrain does not alter terrain style
Branch End Path
Feature Feature alignmentalignment
IntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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d : Deformation energy from TPS warping
g : Graphcut seam cost f : Feature dissimilarity i : Other user specified
constraints
Feature Patch Feature Patch MatchingMatching
IntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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SSD- based search (accelerated)
Fill the synthesized height map
Non-feature Non-feature placementplacement
IntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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GraphcutGraphcut
Graphcut Textures: Image and Video Synthesis Using Graph Cuts (Kwatra et al. 2003)
IntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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Poisson interpolationPoisson interpolation
Poisson image editing (Perez et al. 2003)
Modify the gradient and reconstruct
IntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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Mount JacksonMount Jackson
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Grand CanyonGrand Canyon
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Flathead National Flathead National Forest, MTForest, MT
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Mount Vernon, Mount Vernon, KYKY
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Middle EarthMiddle Earth
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ConclusionConclusion
We’ve presented an image-based algorithm for terrain synthesis
It provides user control by intuitive sketch It preserves terrain style embedded in the original
height field
IntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion
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Cape Girardeau, Cape Girardeau, MO (failed)MO (failed)
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ResultsResults
Show video
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PPA in actionPPA in actionIntroductionIntroductionFeature extractionFeature extractionFeature matchingFeature matchingPatch stitchingPatch stitchingConclusionConclusion