Colophon

The city behind the home page is the Walled City of Lahore, 1.6 by 1.9 km with Badshahi Mosque, Lahore Fort and Wazir Khan Mosque inside it, and Minar-e-Pakistan in the park to the north. A Python pipeline builds it from open data: 10,066 building footprints from Google Open Buildings, with heights from its 2.5D Temporal dataset, and 117.2 km of streets, with the green spaces and the outlines of the landmarks, from OpenStreetMap.

Satellite heights cannot see anything as thin as a minaret, so the domes and minarets of the three landmarks are generated from their outlines, published dimensions and the height data. From all of it the pipeline samples 224,298 points for the scene.

The scene data is published under the Open Database License 1.0. Its manifest lists every file with its sources, their licences, its size and its checksum.

The scene is drawn by a small WebGL2 renderer written for this site, with no 3D library: 19.9 KB of JavaScript, shaders included, loaded only once the page is idle. The points stream in by distance from the centre and are drawn as they arrive, so the sweep that reveals the city is its real loading progress. A camera on a spline follows your scroll through a damped spring, a few cars move along the major roads, and the quality steps down on a slow device until, if it must, the map takes over.

The light is computed in your browser for this moment in Lahore: the sun's position from the US Naval Observatory's approximate solar coordinates, and the moon's from Meeus, both tested against JPL Horizons. By night the city is lit by the moon, if it is up, and by its streetlights; by day by the sun, with shadows drawn from where it stands; and dawn and dusk between. The readout at the foot of every page shows the moon's phase the scene is using, and the theme follows the same sunrise and sunset unless you choose one.