Thanks for your comment. I already use exit portals and have only 2 light layers. In fact, Sun+Sky is layer 0, and all the lights are on the same emitter material, so, the same layer1
In fact, light is entering from the left, and on the glass you see on the left, there are 2 glasses of 1 cm each, with a 7cm gap between each. I think the difficulty is for the light to go through the 2 consecutively. Anyway, i have time for the moment
i render these just for my pleasure.
I think using an exr could be nice, i usually like to have a sun entering windows and having high contrasts on materials, but for this one scene, i think i ll try it next week.
No problem for your english, you can speak french when you don t know how to say things
here is the built version of the project, the architect i worked with sent me the image i forgot to post it for you