Request for advice/help solving a light leaking issue


I have a custom building mesh, this has an exterior and interior, its for a game not an archviz scene. The issue I am having is light hitting the side of the building on an upper level and leaking down the wall into the room below. I will upload a screenshot.

I have made the roof to this part of the building approx 30cm thick, it consists of two planes, one facing upwards (the roof) and then the ceiling 30cm below facing downwards. I have tried both snapping them in each corner to the walls surrounding so that it perfectly lines up with the walls, as well as actually cutting the mesh and welding them to the walls so that there is a gap in the walls between the roof and ceiling, but the like still moves down the wall.

It seems to be caused by the movable light source (directional light) and the only two things that fix it are changing the shadow bias from around 0.5 to around 0.15 but that leaves very undesirable results elsewhere, or changing the Num Dynamic Shadow Cascades from 3 to around 5, but that is quite expensive is it not.

I was just wondering if someone could elaborate on best practice and possible solutions/ ways to avoid this issue when creating other meshes as well as any other ways to fix this that I havent thought about. Thank you very much in advance!



Since you’re using movable lights the only way to adjust that is to adjust the shadow bias. You could try and increase the thickness of the ceiling/roof and cover it up a bit

Hey Darth,

Really appreciate that, honestly I was hoping that was the case, clear and simple issue, so I guess it is like I thought just one of those bite the bullet and pick the worse of two evils really, appreciate your time, thank you!