Since Dialux is not a full-fledged 3d software, Blender is a capable, free, and open-source 3d software. why not develop an addon for Dialux on Blender?

It goes like this.

In Blender,

Create the building or the site, separate the rooms, and add objects and materials. In the addon give a reflection rate for the walls ceiling floor, and furniture(s) then export it as a Dialux file

In Dialux,

Import the Dialux file created in Blender, add luminaires, and define calculation surfaces.

Calculate.

I know it's easier said than done, however, I think this is logical and doable.

You just need to let the addon recognize the ceiling height, the walls, doors, windows, and the reflection rate.