Grenoble Openworld

A 3D open-world recreation of Grenoble built from real geospatial data — OpenStreetMap + IGN RGE ALTI — running in Godot 4.6.

Walk through the streets, fly over the mountains, and explore a procedurally generated city with real building footprints, roads, forests, and terrain.

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Features

• Terrain — 1024×1024 heightmap from IGN RGE ALTI® DTM (1 m resolution, adaptive smoothing), covering a 10 km × 10 km area around Grenoble city centre
• Buildings — ~10 000 extruded footprints from OSM with correct heights; facade atlas shader with 8 material slots (haussmannien, béton 70s, moderne, industriel…), procedural windows and doors
• Roads — PBR asphalt shader with French IISR markings (edge lines + T1 centre dashes); cross-section profile with 15 cm curbs; LOD ribbon at distance; bridge deck height interpolation with 1 m railings
• Sidewalks — offset ribbon meshes at +15 cm (curb height), procedural concrete paving slab shader; presence inferred from OSM sidewalk tag or road category
• Water — animated procedural water shader (dual-scrolling sine-wave normals in world space, blue-green tint, high specular) for rivers, canals, and lakes
• Landuse — terrain overlay polygons (forest, park, farmland, sports, wetland, industrial) from OSM
• Trees — 3 mesh silhouettes (generic deciduous, conifer, broad-crown); non-uniform scale from OSM height + diameter_crown; age factor from start_date; forest polygon scatter + individual OSM nodes; MultiMesh LOD (3D mesh < 600 m → billboard < 1400 m)
• Street furniture — MultiMesh spawner for OSM-tagged street lamps, benches, bins, bus stops, and bike racks; LOD 300 m; orientation from OSM direction tag
• Player — Walking mode (gravity, jump) and free-fly noclip, toggled with F4

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Tech stack

Layer	Technology
Game engine	Godot 4.6 — GL Compatibility renderer, Jolt Physics
Game logic	GDScript
Rendering	Custom spatial shaders: facade, road, sidewalk, water
Data pipeline	Python 3.12 in isolated venv
OSM parsing	osmium 4.3.0
Geodata	rasterio, pyproj, shapely
Image processing	Pillow, numpy

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Data sources

Source	Content
OpenStreetMap (Geofabrik Rhône-Alpes)	Buildings, roads, landuse, trees, street furniture
IGN RGE ALTI® 1 m (WMTS)	Terrain elevation — true DTM (buildings excluded)

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Project structure

grenoble-openworld/
├── autoloads/
│   ├── WorldConfig.gd        # World dimensions, LOD distances, elevation metadata
│   └── WorldEvents.gd        # Signal bus for decoupled spawner communication
├── data/                     # Generated assets (not committed — run pipeline first)
│   ├── heightmap.png / .json
│   ├── buildings.geojson
│   ├── landuse.geojson
│   ├── landuse_texture.png
│   ├── roads.geojson
│   ├── trees.geojson
│   ├── furniture.geojson
│   └── facade_atlas.png
├── scenes/
│   └── main.tscn
├── scripts/
│   ├── Terrain.gd               # Heightmap → mesh + landuse texture overlay
│   ├── BuildingSpawner.gd       # Reads buildings.geojson, instantiates meshes
│   ├── BuildingMeshFactory.gd   # Extruded polygon mesh with UV mapping
│   ├── BuildingMaterialLibrary.gd # OSM tag → facade shader slot per building
│   ├── RoadMeshSpawner.gd       # Road cross-section profile + waterway ribbons + bridges
│   ├── SidewalkSpawner.gd       # Sidewalk offset ribbons with paving slab shader
│   ├── LanduseMeshSpawner.gd    # Landuse polygon overlays (water uses animated shader)
│   ├── ForestSpawner.gd         # 3-type MultiMesh tree scatter (forest + OSM nodes)
│   ├── FurnitureSpawner.gd      # Street furniture MultiMesh (lamp, bench, bin, …)
│   ├── ChunkManager.gd          # Chunk loading infrastructure (streaming-ready)
│   └── NoclipPlayer.gd          # Walking mode + noclip camera
├── shaders/
│   ├── facade.gdshader          # Procedural windows + doors, 8-slot atlas
│   ├── road.gdshader            # PBR asphalt + French IISR markings
│   ├── sidewalk.gdshader        # Concrete paving slab grid
│   └── water.gdshader           # Animated wave normals, specular reflections
└── tools/
    ├── config.py                # Pipeline config (centre, radius, all output paths)
    ├── setup.sh                 # Create venv + install dependencies
    ├── download_osm.py          # Download Rhône-Alpes PBF, clip to bbox
    ├── download_dem_ign.py      # Download IGN RGE ALTI tiles via WMTS
    ├── process_dem.py           # DEM → heightmap PNG + JSON (adaptive smoothing)
    ├── extract_buildings.py     # OSM PBF → buildings.geojson
    ├── extract_landuse.py       # OSM PBF → landuse.geojson
    ├── extract_roads.py         # OSM PBF → roads.geojson (incl. bridge, sidewalk, lanes)
    ├── extract_trees.py         # OSM PBF → trees.geojson (incl. genus, crown, age)
    ├── extract_furniture.py     # OSM PBF → furniture.geojson (lamp, bench, bin, …)
    ├── generate_facade_atlas.py # Build 8-slot facade texture atlas (CC0 sources)
    ├── generate_landuse_texture.py # Rasterise landuse polygons → PNG overlay
    └── export_to_godot.py       # Copy all pipeline outputs to data/

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Setup

Prerequisites

• Godot 4.6+
• Python 3.12+

1 — Data pipeline

cd tools
bash setup.sh
source venv/bin/activate

# Downloads (~500 MB OSM PBF + IGN DEM tiles, takes 20–40 min)
python download_osm.py
python download_dem_ign.py

# Terrain processing
python process_dem.py

# OSM extraction
python extract_buildings.py
python extract_landuse.py
python extract_roads.py
python extract_trees.py
python extract_furniture.py

# Asset generation
python generate_facade_atlas.py
python generate_landuse_texture.py

# Copy everything to data/
python export_to_godot.py

2 — Run

Open project.godot in Godot 4.6 and press Play.

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Controls

Key	Action
WASD	Move
Mouse	Look
Shift	Sprint
Space	Jump (walk mode)
F4	Toggle noclip / walk
Escape	Release mouse
Scroll wheel	Adjust noclip speed

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Coordinate system

All pipeline scripts and Godot scripts share the same convention:

Space	Convention
Source data	WGS84 (lat/lon)
Pipeline + GeoJSON	Local UTM 31N metres, origin = world centre
Godot	X = east, Y = up, Z = south (northing flipped)

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Roadmap

Phase	Status	Content
1	✅	LOD infrastructure, ChunkManager, per-system LOD distances
2	✅	IGN RGE ALTI terrain, facade atlas with 8 material slots
3	✅	PBR road shader (IISR markings), curb cross-section, sidewalks
4	✅	Animated water shader, bridge deck interpolation + railings
5	✅	3-type tree silhouettes, non-uniform scale, street furniture
6	⬜	HDR sky, atmospheric haze
7	⬜	Day/night cycle