Demo: Build City Mesh from CityJSON¶

This demo illustrates how to build a mesh for a CityJSON city model.

To run the demo, type:

$ python build_city_mesh_from_cityjson.py

Purpose¶

This demo demonstrates how to download a CityJSON file from an external URL, load the city model from the file using DTCC, build a city mesh at a specified level of detail (LOD2 in this case), and visualize the resulting mesh.

Step-by-step¶

Download CityJSON File: Retrieve the CityJSON file from a specified URL and save it to a temporary file. This file contains the city model data in the CityJSON format.

url = "https://3d.bk.tudelft.nl/opendata/cityjson/3dcities/v2.0/3-20-DELFSHAVEN.city.json"
temp_path = tempfile.NamedTemporaryFile(suffix=".json", delete=False)
urlretrieve(url=url, filename=temp_path.name)

Load City Model: Load the city model from the downloaded CityJSON file using the load_city function provided by DTCC.
```
import dtcc
city = dtcc.load_city(temp_path.name)
```
Add terrain to the city model If the model doesn’t have a terrain, add a flat terrain to the city model with a buffer of 10 meters.
```
if not city.has_terrain():
   city.add_flat_terrain(buffer=10)
```
Build City Mesh: Generate a city mesh from the loaded city model. Here, the mesh is built at level of detail LOD2.
```
mesh = dtcc.build_city_mesh(city, dtcc.GeometryType.LOD2)
```
Visualize the Mesh: View the generated city mesh using the view() method.
```
mesh.view()
```
Delete Temporary File: Clean up by deleting the temporary file.
```
os.unlink(temp_path.name)
```

Complete Code¶

Below is the complete code for this demo:

# This demo illustrates how to build a mesh for a CityJSON city model.

import dtcc
from urllib.request import urlretrieve

# Download example CityJSON file
url = "https://3d.bk.tudelft.nl/opendata/cityjson/3dcities/v2.0/3-20-DELFSHAVEN.city.json"
urlretrieve(url=url, filename="city.json")

# Load city model from CityJSON file
city = dtcc.load_city("city.json")

# Add terrain if not present
if not city.has_terrain():
    city.add_flat_terrain(buffer=10)

# Build city mesh
mesh = dtcc.build_city_mesh(city, dtcc.GeometryType.LOD2)

# View mesh
mesh.view()