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Street Generation for City Modeling. Xavier Décoret, François Sillion iMAGIS GRAVIR/IMAG - INRIA. Foreword. A Computer Graphics point of view Graphic artists Game developers Researchers A work in 2 parts A framework An algorithm. Motivations. - PowerPoint PPT Presentation
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Street GenerationStreet Generationfor City Modelingfor City Modeling
Xavier Décoret, François SillionXavier Décoret, François Sillion
iMAGIS GRAVIR/IMAG - INRIAiMAGIS GRAVIR/IMAG - INRIA
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A Computer Graphics point of viewA Computer Graphics point of view– Graphic artistsGraphic artists
– Game developersGame developers
– ResearchersResearchers
A work in 2 partsA work in 2 parts– A frameworkA framework
– An algorithmAn algorithm
ForewordForeword
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MotivationsMotivations
City Modeling is a growing field of interestCity Modeling is a growing field of interest– Game and LeisureGame and Leisure
» Virtual environments are widely usedVirtual environments are widely used
» Need for larger environmentsNeed for larger environments
» Cities are natural and appealing large environmentsCities are natural and appealing large environments
– Analysis and SimulationAnalysis and Simulation» Pedestrians or traffic flowPedestrians or traffic flow
» Wave transportationWave transportation
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MotivationsMotivations
Creating the virtual model is a tedious taskCreating the virtual model is a tedious task– Realistic modelRealistic model
» Model it by hand: long and costlyModel it by hand: long and costly
» Reconstruct it automatically: not working yetReconstruct it automatically: not working yet
– Semi-realistic modelSemi-realistic model» Procedural modellingProcedural modelling
» Map is exact, geometry is approximativeMap is exact, geometry is approximative
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MotivationsMotivations
Creating the virtual model is a tedious taskCreating the virtual model is a tedious task– Realistic modelRealistic model
» Model it by hand: long and costlyModel it by hand: long and costly
» Reconstruct it automatically: not working yetReconstruct it automatically: not working yet
– Semi-realistic modelSemi-realistic model» Procedural modellingProcedural modelling
» Map is exact, geometry is approximativeMap is exact, geometry is approximative
No existing tool
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Overview of the toolOverview of the tool
Retrieve the 2D footprints of buildingsRetrieve the 2D footprints of buildings– Aerial photographsAerial photographs
– Existing 2D models Existing 2D models
Procedurally generate buildingsProcedurally generate buildings– Grammar, library of shapesGrammar, library of shapes
– Style information provided by a designer (GIS)Style information provided by a designer (GIS)
Generate streetsGenerate streets– Retrieve the street networkRetrieve the street network
– Generate geometryGenerate geometry
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Overview of the toolOverview of the tool
Retrieve the 2D footprints of buildingsRetrieve the 2D footprints of buildings– Aerial photographsAerial photographs
– Existing 2D models Existing 2D models
Procedurally generate buildingsProcedurally generate buildings– Grammar, library of shapesGrammar, library of shapes
– Style information provided by a designer (GIS)Style information provided by a designer (GIS)
Generate streetsGenerate streets– Retrieve the street networkRetrieve the street network
– Generate geometryGenerate geometry
Our contribution
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Input & OutputInput & Output
Input
Output
Polygonal footprints
+
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PrinciplePrinciple
We use a median axis (skeleton)We use a median axis (skeleton)
Seems natural for roadsSeems natural for roads– Goes in between 2 buildingsGoes in between 2 buildings
– Goes approximately at equal distanceGoes approximately at equal distance
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Use of a median axisUse of a median axis
Street graphPolygonal footprints
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Robustness Issues (1)Robustness Issues (1)
Input sensitivityInput sensitivity
Ideal case Noise effect Expected result
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Robustness Issues (2)Robustness Issues (2)
ArtefactsArtefacts
Unwanted branches requiring post-processing
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Our approachOur approach
A topological phaseA topological phase– Partition Partition the map intothe map into
» StreetsStreets
» CrossingsCrossings
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Our approachOur approach
A topological phaseA topological phase– Partition Partition the map intothe map into
» StreetsStreets
» CrossingsCrossings
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Our approachOur approach
A topological phaseA topological phase– Partition Partition the map intothe map into
» StreetsStreets
» CrossingsCrossings
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3399
44
55
6677
88
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Our approachOur approach
A topological phaseA topological phase– Partition Partition the map intothe map into
» StreetsStreets
» CrossingsCrossings
A geometric phaseA geometric phase– The graph is shaped to a The graph is shaped to a
correct positioncorrect position
– Optimisation with constraintsOptimisation with constraints
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33
44
55
6677
8899
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Our approachOur approach
A topological phaseA topological phase– Partition Partition the map intothe map into
» StreetsStreets
» CrossingsCrossings
A geometric phaseA geometric phase– The graph is shaped to a The graph is shaped to a
correct positioncorrect position
– Optimisation with constraintsOptimisation with constraints
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33
44
55
6677
8899
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Topological PhaseTopological Phase
Sample the footprints with extra verticesSample the footprints with extra vertices
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Topological PhaseTopological Phase
Sample the footprints with extra verticesSample the footprints with extra vertices
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Topological PhaseTopological Phase
Sample the footprints with extra verticesSample the footprints with extra vertices
Delaunay triangulate the samplesDelaunay triangulate the samples
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Topological PhaseTopological Phase
Sample the footprints with extra verticesSample the footprints with extra vertices
Delaunay triangulate the samplesDelaunay triangulate the samples
Ignore edges joining samples of a same buildingIgnore edges joining samples of a same building
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Topological PhaseTopological Phase
Sample the footprints with extra verticesSample the footprints with extra vertices
Delaunay triangulate the samplesDelaunay triangulate the samples
Ignore edges joining samples of a same buildingIgnore edges joining samples of a same building
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Topological PhaseTopological Phase
Sample the footprints with extra verticesSample the footprints with extra vertices
Delaunay triangulate the samplesDelaunay triangulate the samples
Ignore edges joining samples of a same buildingIgnore edges joining samples of a same building
Take the dual of edges (Voronoï diagram)Take the dual of edges (Voronoï diagram)
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Topological PhaseTopological Phase
Sample the footprints with extra verticesSample the footprints with extra vertices
Delaunay triangulate the samplesDelaunay triangulate the samples
Ignore edges joining samples of a same buildingIgnore edges joining samples of a same building
Take the dual of edges (Voronoï diagram)Take the dual of edges (Voronoï diagram)
Construct a graph from the edgesConstruct a graph from the edges
Crossings
Streets
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Our approachOur approach
A topological phaseA topological phase– Partition Partition the map intothe map into
» StreetsStreets
» CrossingsCrossings
A geometric phaseA geometric phase– The graph is shaped to a The graph is shaped to a
correct positioncorrect position
– Optimisation with constraintsOptimisation with constraints
99
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Geometric PhaseGeometric Phase
Place sample Place sample medianmedian points points
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Geometric PhaseGeometric Phase
Place sample Place sample medianmedian points points
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Geometric PhaseGeometric Phase
Place sample Place sample medianmedian points points
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Geometric PhaseGeometric Phase
Place sample Place sample medianmedian points points
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Geometric PhaseGeometric Phase
Place sample Place sample medianmedian points points
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Geometric PhaseGeometric Phase
Place sample Place sample medianmedian points points
Compute minimum widthCompute minimum width
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Geometric PhaseGeometric Phase
Place sample Place sample medianmedian points points
Compute minimum widthCompute minimum width
Greedily place a Greedily place a validvalid polyline in between polyline in between
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Geometric PhaseGeometric Phase
Place sample Place sample medianmedian points points
Compute minimum widthCompute minimum width
Greedily place a Greedily place a validvalid polyline in between polyline in between
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Place sample Place sample medianmedian points points
Compute minimum widthCompute minimum width
Greedily place a Greedily place a validvalid polyline in between polyline in between
Split the polyline inSplit the polyline in– SegmentsSegments
– CurvesCurves
Geometric PhaseGeometric Phase
Segments
Curve
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RobustnessRobustness
A topological phaseA topological phase– Partition Partition the map intothe map into
» StreetsStreets
» CrossingsCrossings
A geometric phaseA geometric phase– The graph is shaped to a The graph is shaped to a
correct positioncorrect position
– Optimisation with constraintsOptimisation with constraints
- Based on distance- Robust to footprints’shape- Solves input sensitivity
- Based on optimisation- Robust to footprints’shape- Solves artefacts
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ResultsResults
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Street GenerationStreet Generation
Generate streetsGenerate streets– Retrieve the street networkRetrieve the street network
» TopologyTopology
» Simple primitivesSimple primitives
– Generate geometryGenerate geometry» Match buildings boundariesMatch buildings boundaries
» Connect correctly at crossingsConnect correctly at crossings
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WorkflowWorkflow
Generate streetsGenerate streets– Retrieve the street networkRetrieve the street network
» TopologyTopology
» Simple primitivesSimple primitives
– Generate geometryGenerate geometry» Match buildings boundariesMatch buildings boundaries
» Connect correctly at crossingsConnect correctly at crossings
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Generating geometryGenerating geometry
Use library of parametric modelsto build segments and curves
Triangulate the remaining border
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Parametric modelParametric model
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ResultsResults
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Conclusion & Future WorksConclusion & Future Works
We can generate geometry from a 2D map of We can generate geometry from a 2D map of buildingsbuildings
– Work in 2D1/2Work in 2D1/2
Write more parametric modulesWrite more parametric modules
High level features extractionsHigh level features extractions– AvenuesAvenues
– SquaresSquares
Generate coherent trafic signsGenerate coherent trafic signs
