Comment by BenoitEssiambre

What I'm trying to achieve is lighting a bit like in these "Artificial Skylight" concepts: https://architizer.com/blog/practice/materials/let-there-be-... They claim their technology is about "Rayleigh scattering" but I think that's mostly marketing mumbo jumbo. Sure that might add a bit of diffuse blue but their main secret, I would bet, is parallel rays which explains why their fixtures require so much space above the ceiling to get around conservation of etendue. The effect of parallel rays and sharp shadows are definitely represented in their example pictures.