Bật đèn trước khi xâySwitching the lights on before the house is built

A reflected ceiling plan says where each light sits and which switch it hangs on. It does not say what the living room will look like at night, and most owners cannot read it anyway. A render shows a mood, but not whether there is enough light to read by or to see the stair treads. For a narrow terraced house ("nhà phố") still in design, we wanted the owner and the designer to look at the same picture before deciding where the lights go.

What we built

A viewer paints simulated illuminance (in lux) onto the interior image itself. Bright and dark areas show as false colour, with lux contour lines on top. Beside it are six switches, one for each group of lights on the drawing: living downlights, cove LED, painting light, dining downlights, dining pendant with wall lights, and the spots over the void. Press a switch and the picture changes at once, as if the light had been turned on. Six switches give 64 combinations, and a visitor can try all of them.

How we worked

We started from the ceiling plan in DWG, the approved interior renders and the owner's questions. We took the positions of 154 luminaires from the drawing, placed them in the 3D model and checked them back against the plan. The light was computed in Radiance, a validated lighting engine, once for each group. The viewer combines those results according to which switches are on.

An AI coding agent (Claude Code) worked alongside us on this project. It helped write the code that reads the drawings, builds the model, runs the simulation and builds the viewer, and it wrote the automated checks; most commits in the project's git history name it as co-author. The architect set the questions. The architect also checked the results against the drawings and decided whether to trust them.

What it helped decide

The owner raised six questions, and each got a picture to answer it. A 9 W downlight is about 29% brighter than a 7 W one, under the assumed light output. Over the dining table, one long pendant lets the six downlights stay off at dinner. On the mezzanine stair, two wall-washing lights cover most of the stairwell, but one hidden corner of a tread still falls short of 100 lux. The model reports those shortfalls too, because the owner needs to know before construction.

Limits

We had no photometric data for the actual luminaires, so we assumed a light output (about 750 lm for a 9 W downlight). Surface reflectances are estimated, and nothing has been measured in the finished house. Every value here is a simulation. In this view the kitchen has no lux map, so the kitchen frame stays dark.

The interactive version is in the Computational Design row of the Work page.