Trafalgar Square, sun hours on 21 June

Method

Archi Automate output, unretouched. The clip comes straight out of the Archi Automate viewer: viewer_record rendered each frame from the sun study’s time series. It is not a screen capture, and the title, legend, compass, scale bar and site clock are drawn by the viewer. The whole day, 04:45 to 21:15 BST, runs in 10 seconds. Colours are hours of direct sun since sunrise, from 0 to 16.5 h, the longest possible day at this site in 15-minute steps. The square tile loop is different: viewer_record only records 16:9, so it is 67 viewer captures, one per 15-minute step, joined into a video with ffmpeg; it shows the last 8 seconds of the day.

How it was made: ifc_import_context brought 1,891 OpenStreetMap elements within 350 m into a new IFC model in 48 seconds: buildings with their height and building parts, roads, squares, fountains, monuments (Nelson’s Column at 51.6 m) and trees. The assistant added 8,873 ground tiles of 2 m with ifc_run_write_task. sim_sun then computed the sun on every tile and element every 15 minutes on 21 June 2026, in British Summer Time. The study ran on Archi Automate 27.35 and was run three times while the tiles were raised and the grid extended. The recording was made on 27.36, from the same results. On this day the tiles average 10.0 hours of sun (median 11 h, at most 14.5 h).

Between the 15-minute steps the viewer blends the hours and the clock runs on. During the day it also draws the shadow of that moment over the running total, so tiles in shade at that moment look a little darker than the legend. After sunset the colours match the legend on 99.8% of visible tiles.

Limits

• 184 of the 574 buildings and building parts have no height in OpenStreetMap and use a 9 m default. Among them is St Martin-in-the-Fields, so its spire is missing and its shadow is too short.
• Trees use one default size.
• Sun hours are counted per 2 m tile from one point at its centre, and per element for buildings; context buildings are shown grey, not analysed.
• This is an analysis aid, not a planning or daylight report.