Demo: Simplify Building Footprints¶

This demo demonstrates how to simplify and process building footprints. It covers downloading point cloud and building footprint data, removing outliers, building a terrain raster, extracting roof points, computing building heights, and then simplifying and splitting the building footprints for a cleaner city model.

To run the demo, type:

$ python simplify_building_footprints.py

Purpose¶

This demo illustrates an end-to-end workflow for processing building footprints. It demonstrates how to: - Download point cloud and building footprint data. - Process the point cloud by removing outliers. - Build a terrain raster from the point cloud. - Extract roof points and compute building heights. - Simplify building footprints through merging, simplification, and clearance fixing. - Optionally split footprint walls based on building height. - Assemble a city model and visualize the result.

Step-by-step¶

Define Bounds: Specify the spatial bounds for a residential area in Helsingborg by setting a height/width value (here, 2000.0 units).
```
h = 2000.0
bounds = dtcc.Bounds(319891, 6399790, 319891 + h, 6399790 + h)
```

Download Data: Retrieve the point cloud and building footprint data within the defined bounds.

pointcloud = dtcc.download_pointcloud(bounds=bounds)
buildings = dtcc.download_footprints(bounds=bounds)

Process the Point Cloud: Remove global outliers from the point cloud to improve data quality.
```
pointcloud = pointcloud.remove_global_outliers(3.0)
```

Build Terrain Raster: Create a terrain raster from the processed point cloud. Parameters such as cell size, radius, and ground filtering are specified.

raster = dtcc.build_terrain_raster(pointcloud, cell_size=2, radius=3,
                                   ground_only=True)

Extract Roof Points and Compute Building Heights: Process the building footprints to extract roof points and compute building heights based on the terrain raster.
```
buildings = dtcc.extract_roof_points(buildings, pointcloud)
buildings = dtcc.compute_building_heights(buildings, raster, overwrite=True)
```

Simplify Building Footprints: Merge, simplify, and fix clearances in the building footprints to clean up the data.

buildings = dtcc.merge_building_footprints(buildings, max_distance=0.5,
                                           min_area=10)
buildings = dtcc.simplify_building_footprints(buildings, tolerance=0.25)
buildings = dtcc.fix_building_footprint_clearance(buildings, 0.5)

Split Footprint Walls: Optionally split building footprint walls using the building heights to determine maximum wall length.

max_wall_length = [building.height for building in buildings]
buildings = dtcc.split_footprint_walls(buildings, max_wall_length=max_wall_length)

Create and Visualize the City Model: Create a city object, add the processed building footprints, and visualize the resulting city model.
```
city = dtcc.City()
city.add_buildings(buildings)
city.view()
```

Complete Code¶

Below is the complete code for this demo:

import dtcc

# Define bounds (a residential area in Helsingborg)
h = 2000.0
bounds = dtcc.Bounds(319891, 6399790, 319891 + h, 6399790 + h)

# Download pointcloud and building footprints
pointcloud = dtcc.download_pointcloud(bounds=bounds)
buildings = dtcc.download_footprints(bounds=bounds)

# Remove global outliers
pointcloud = pointcloud.remove_global_outliers(3.0)

# Build terrain raster
raster = dtcc.build_terrain_raster(pointcloud, cell_size=2, radius=3, ground_only=True)

# Extract roof points and compute building heights
buildings = dtcc.extract_roof_points(buildings, pointcloud)
buildings = dtcc.compute_building_heights(buildings, raster, overwrite=True)

# Simplify building footprints
buildings = dtcc.merge_building_footprints(buildings, max_distance=0.5, min_area=10)
buildings = dtcc.simplify_building_footprints(buildings, tolerance=0.25)
buildings = dtcc.fix_building_footprint_clearance(buildings, 0.5)

# Split building footprints walls
max_wall_length = [building.height for building in buildings]
buildings = dtcc.split_footprint_walls(buildings, max_wall_length=max_wall_length)

# Create city and add buildings
city = dtcc.City()
city.add_buildings(buildings)

# View city
city.view()