Strange light differences with UE4's inbuilt Geometry

Hi all,

Here’s a little lighting issue that’s got me scratching my head. I am finding that there is a difference in the light being picked up on the Geometry in UE4. To show what I mean, take this picture:


Notice how at the end of the room the floors and walls appear much brighter in the background than the ones in the foreground. It doesn’t matter how you move around, or how you deal with the lights, that end of the room is always has a brighter contrast. Yet the textures they have are the same and if anything, there is slightly less light at that end of the room then at the other.

But here is the weird thing, the meshes there are unaffected, it is just textures applied to the basic geometry I used to build the walls and floor (ruling out Lightmap issues on the meshes which I managed to sort last week after some more head scratching and little help from the forums). Indeed, there are light sources right on the join as well, which are the same type (done via blueprint) as all other light sources in the room. Technically, they should light up both sides in the same way, but they don’t.

It is also happening in the room above as can be seen in this picture (I’ve just begun work on this room, so forgive the lack of detail and the over powered materials with emitters, all of this is work in progress):


The bright section appears in exactly the same location, just directly above the other room. I’ve had a look and can’t find any rogue anomalous lights either (and even if there were, this would mean the light was penetrating solid walls).

Indeed, if we come outside of the rooms for a minute, we can even see it is affecting the outside as well (please also note the yellow box on this image which shows the Lightmass importance has been added and covers the whole level):


I’ve ensured the textures are aligned though, I’ve even deleted those brighter areas and pulled copies of the geometry from the rest of the level into those areas and I’ve rebuilt the lighting umpteen times. Still, this pesky sharp contrast persists. I’m sure it’s something I’ve missed, but I can’t tell what.

But to sum up:
It only seems to be affecting UE4’s geometry.
The level has a lightmass importance covering everything
Textures are identical and aligned.
Lights have been rebuilt.
The contrast remains tied to that side of the level.
There are no ‘rogue’ lights.

Any ideas?


I´ve got exactly the same problem using UE 4.3. If I place 4 pieces with the same material and snap them via vertex snap together in the normal 3rd person level outside, everything looks okay. As soon as I build walls and ceiling around them /building a simple room, I get this very odd color difference. It is as though it isn´t using pixel lighting anymore but some strange kind of “object” lighting (light&dark) :-/ .

@ Draken_28: By “geometry” do you mean brushes or static mesh pieces. I was using the standard static mesh pieces in the Arch-Folder.

Thankful for any help,

This post may help a little from another thread:

This is a known problem with modular pieces. Using other geometry to hide the seams or brighter lights to not bake as much shadow information is a good start way to directly hide the seams. Using Daniel’s suggestions by adjusting the IndirectLightingSmoothness and IndirectLightingQuality can help as well.

Give that a shot and see what works best for you. :slight_smile:


DanielW could probably give you a much more technical explanation than I could but from what I understand it’s that the light is being rendered on different threads that is causing the issues with lightmass. Using the methods above will help the seams.

UE4 uses deferred rendering for its lighting as opposed to UE3’s forward rendering. Using the techniques above and an increased lightmap size can help though.

Thanks for the tips everyone. I used the brushes in game for the floors and walls (the static meshes weren’t affected, just the brushes). I actually solved it in the end by grab everything and moving it’s relative location in the level, dragging it out of the bright area. The difference in lighting was too high to be able to just hide with static meshes and turning up the lighting was not really the effect I was looking for, I wanted to keep the lighting low to achieve the ambience shown in this picture:


It does seem odd though that there would be this patch in the level that for some reason was brighter than the rest of the level without anything telling it to be brighter. And whilst it seems lined up with a brush seam there, during trying to solve it, I discovered that brushes half over the patch would also be half higher lit and half normal lit, so not quite sure if it really is a seam problem