Buildings can be mapped in OpenStreetMap. Their shapes can be turned into 3D models for use in FlightGear scenery.

Challenges

• There are "just" 64 million buildings in OSM^[1], most cities in the world have no buildings at all or just a few.
• Only 1.04% of the buildings in OSM have a height specified. Ca. 1.4% has a known number of floors (levels).^[2]
• FlightGear cannot handle thousands of models in a view. Grouping models into bigger files improves performance to a very usable level, but is less practical unless automated.

From OpenStreetMap

A single building

1. Find the building in OpenStreetMap.
2. Enable the "Data" overlay.
3. Choose a manual area and drag a box around your building.
4. Click your building, the way id will be shown. Copy this id.
5. Run the following code, replacing 44338398 with your building's id:

perl bob.pl -w 44338398

Next to this basic code, there are several options, to be added behind the basic code.

• Lat/lon location of the model's origin:

-lat 52.00141 -lon 4.36966

• Object name (not the .ac name!):

-n "Empire State Building"

• Building height (in meters):

-h 15

Note: buildings are always sunk 5 m into the ground, in order to account for non-flat terrain. These 5 meters are added on top of (or below, if you like) the building height.

• Create a xml file with a standard range animation:

-x

• Clean the shape by removing nodes that lie within a certain distance from the line that connects its two adjacent nodes. This results in much smaller files and allows more buildings to have a gable roof:

-clean

All buildings in an area

  Lower Manhattan at dawn.

1. Download a file with all data from the area, by visiting the following link and save it somewhere on your computer. This will only include buildings (building=yes) within the specified bounding box.

   http://overpass-api.de/api/xapi?way[bbox=left,bottom,right,top][building=*][@meta]

   For example:

   http://overpass-api.de/api/xapi?way[bbox=-74.02037,40.69704,-73.96922,40.73971][building=*][@meta]

2. Get a list of wayids via grep "<way" map.osm|cut -f2 -d\">wayids.txt change the number after f where appropriate
   or sed -n 's|<way.*id="\(.*\)" .*>|\1|p' "map.osm" > wayids.txt
3. For Windows users: Run for /f %a in (wayids.txt) do perl bob.pl -w %a -f map.osm
   For others: Iterate through wayids.txt and assign each way id to $object and run perl bob.pl -w $object -f map.osm on all the ids.

参考：https://wiki.flightgear.org/OpenStreetMap_buildings