white the wall become dark?

[vsolutionvs]

May i know why the front wall show darker? Thank you...

[Dariusz Makowski (Dadal)]

Because according to light decay and physics less light hit it...

[LQ2]

It might be also worth noting that I assume there is no GI in the scene and no floor or ceiling, so the lighting solution would be strange anyway. If you were to put a floor and a ceiling, and enable GI, you might be able to get lighting.