Severe light bleeding through walls

Hi guys! I’m pretty new to Unreal and I’m having this issue:

It doesn’t seem like it’s caused by lightmap resolution, because (as you can see from the shadow on the floor) the lightmap resolution is much higher than the bleeding. Also the bleeding has kind of a round falloff.

The walls are interpenetrating with the ceiling and floor, so I’m certain there’s no gaps in between. Here’s my lightmap UVs, in case it helps:


Any thoughts?

The floors and ceiling need to be close solid meshes (not open and one sided), and it’s better if the walls and ceiling meet up exactly instead of interpenetrating.

You are much better off using individual wall meshes as you can then give better quality lightmaps to them which will solve your problem. Your lightmap resolution may be high but its covering all of your walls with a single lightmap and then you get bleeding on the UV.

Hey guys! Sorry about the delayed response. I went back and spent some time messing with this, trying to figure out where and when I’m going wrong. So far I’ve:

-Constructed a new scene out of closed, watertight, non-interpenetrating meshes
-Cranked the lightmap resolution up to 2048
-Build lighting on Production quality

Unfortunately I’m still getting the same problem:

It’s got a roundish falloff that’s much bigger than the texel size–so I don’t think it’s an issue of bleeding across the lightmap UV:

Not to mention this ridiculous issue when I stand near it, haha:

It looks like it’s somehow bouncing around inside the mesh and then bouncing through the backfaces on the other side, even though the wall mesh is now closed and perfectly flush with the floor and walls. Is there anything I can do to prevent this besides making the walls all cartoonishly thick?

You can’t have a surface extending beyond the visible area, in that last situation, the pixels of the lightmap won’t line up with where the wall is, and so you’ll either have shadow pixels extend inside or lit pixels extend outside.

I’m sorry, I don’t think I understand at all :{

What determines the visible area? What am I doing incorrectly?

Is the issue that there are no lights lighting the other side of the wall, so it assumes it’s not meant to be visible + lets it bleed through?

Or do I need to make sure my walls align perfectly to the texels of the lightmap? Still kind of mystified here, haha.

Your surface can’t extend beyond the visible area, the part that’s not visible will receive shadows, so you have a floor with a wall on top of it, but the floor goes underneath the wall. When you build the lighting pixels that are lit will extend underneath the wall and might be visible on the other side, or you might get a shadow underneath the wall which can cause dark pixels to appear on the floor since the mesh can’t line up perfectly with the lightmap.

It’s not worth the trouble to try and line up meshes with lightmap pixels, since you can’t do that with meshes that aren’t rectangular.

So–if I want to make walls and floors and avoid the bleeding, what do I need to do differently?

From what I can see, your first room mesh is correct, your second example is not. I can’t see how the light would bleed over there unless the floor or ceiling go over the space between walls, which it looks like it doesn’t.

Hmm, okay–maybe if I make sure the floor pieces are separated under the walls, AND make sure the floor and walls are all closed solid meshes, then it will work. I’ll try that tonight. :v

Well, the walls don’t need to be capped, but it wouldn’t be bad to have wall/ceiling surfaces facing out like the exterior of the building, but I wouldn’t think that would have an effect on interior lighting.