Pixelated artifacts in lightmaps

Hello, I am trying to bake a bedroom scene. I have already done it in 4.23 and it was pretty fine. In 4.24 it gives me some bright pixel artifacts in areas that should normally be shadowed. It happens not in every shadow but mostly on places that are almost completely covered by something and should be really dark. I uploaded some pictures. One is under the bed, one is behind the curtains and in one i hid the vanity mirror so that you see how the wall behind it is pixelated and bright instead of black.

lightmass settings are pretty high 0,1 scale, 10 and 10 both bounces, 4 quality, 1 smoothness. The meshes it happens on are simple walls or floor which means the unwrap is easy and lightmap res is 1024x1024. Anyway if it works in 4.23 why those artifacts in 4.24?

By the size of the pixels it looks like it might be something else. Some pixels are larger than others. That wouldn’t happen as far as I know. Have you tried to check Detail Lighting and Lighting Only modes to see if it actually is a lighting problem?

Yes, it is exactly the same in Detail Lighting and Lighting Only view modes. Searching on the web I found another post in the forums having a similar problem. A scene that baked fine in 4.23, upgraded to 4.24 and had issues. https://forums.unrealengine.com/deve…build-lighting

Something similar to this post happens to my wardrobe. Look at the pictures 4.23 clean lightmaps, 4.24 dirty lightmpas, on the same mesh, with the same unwrap. Just in 4.24 I have removed many objects for the scene as I was wasting hours testing and testing again thinking that I might fix it by changing various settings, only to find out it was the engine version that is responsible. Unless someone enlightens me with some sort of trick I didn’t know that can fix it.

Is there any update on this issue? as a marketplace creator this is becoming a big issue, should we downgrade to 4.23 in order to bake our scenes and put it in the marketplace?

Have you tried to create a new project in 4.24 and then migrate everything from 4.23 to the new project?

I didn’t have any problems moving from 4.23 to 4.24 so it might be something project specific. I would try to migrate and leave everything at default for the first lighting build. See if the problem occurs. If it doesn’t then start making your project specific changes until it happens again.

Are there stationary or movable lights in the scene? If so, what are the settings? What are Volumetric Lightmap settings in World>Lightmass?

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Were you able to resolve this issue? I recently moved to 4.24 and I’m running into the exact same problem with baked lightmaps. In areas with enough light, the lightmaps look acceptable. But in darker or fully darkened areas the maps look pixelated and corrupted like yours.

I think this looks like a place where a mesh has been placed and then removed after building the lighting. Is there something in the scene that blocked light but is currently not visible? Press Ctrl+H to make all meshes visible. - Just a guess. Sorry if that sounds a bit silly but I made that mistake before multiple times :wink:

I hit the same sort of artifact - was fixed by unchecking “Cast Shadow” on a sky dome static mesh surrounding the scene, even though the mesh had an unlit material and shouldn’t have affected static lighting.

Even an unlit material can have emissive when there’s at least a skylight in the scene. It could be a result of the skylight bouncing off the skydome and contributing its emissive to the light bake, resulting in those artifacts. Not sure if it’s really the cause, or a part of it potentially.

Did it work when you disable the shadows of your sky dome?

If not have you tried to change the FireflyClamping?

Go to your engine instalation and under “\UE_YourVersion\Engine\Config” you will find a file named “BaseLightmass.ini”. At the very end you should have FireflyClamping, change it for a bit less and build the light once again if it doesnt work move it up a little bit more and see what it happens (Change 500 less and then if it doesnt work change to 500 more than it was before)

The other 2 parameters will help your project too but thats another topic and dont go too big on those, also I have seen in the comments for you to change in the world settings but the only parameter that will work with GPU lightmass is the “Num Indirect Lighting Bouce” the secound option.

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Hey all, thanks for the help. I apologize for not responding, I subscribed to this thread but must have done it wrong and never got any email notifications. After this post, I found GPU Lightmass and gave that a try. Using the GPU did not result in these corrupted lightmaps. The GPU tool is more complex to use, but I believe I can make that work and get good results.

Since then, I moved from 4.24 to 4.25. Created a brand new map, and using standard/CPU lightmass, I ended up with the same corrupted lightmaps. The skysphere mesh has cast shadow disabled by default, so that was not the culprit. There are also oddities like spots where it looks like an invisible object is casting a shadow, but I am certain there is no object there. Here’s a picture:

This is a fresh map with mostly BSP. I am 100% sure nothing is there, haha

Some part of me wants to blame my specific CPU. I have a relatively old Haswell-E 8 core i7-5960x. For now I will be relying on GPULightmass. I also have other team members that can build my lighting for production if need be. I’m still open to solutions or ideas for testing if anyone can think of anything. Thanks again!

That shadow looks like it’s a cast of the wall it’s next to, but a really bad one. Is the floor there the default tile material from the starter content? I think it may be a part of the problem. Open it in the mesh editor and check settings under LOD 0 > Build, and the other lighting settings. Is “Generate Mesh Distance Fields” enabled in the project settings? If not, try enabling it, and then for that wall mesh in the picture, go to the mesh editor and change Distance Field Resolution to 2, click Apply if it lights up.

I think you’re right, that black mark is the shadow caused by the wall and the second point light that can be seen in the background. I verified by deleting that point light and rebuilding, which erased that artifact.

Unfortunately all the geometry seen in the picture is BSP, not static mesh.

You say you are using BSP? I haven’t used it for a long time. It can cause problems like that. Try to build geometry. In the past you had to build geometry every time you made a change to the BSP.

Are you building lighting by “Build Lighting Only”? Click on the main icon “Build” instead. That will build everything necessary. You should always do that. I would never build lighting only. You don’t really save any time doing that unless you have a huge game scene with lots of navigation in it or you specifically do not want to build something like navigation (so it doesn’t change).

Yea I am using BSP for the initial blockout. I wanted to highlight the fact that it affects both types of geometry; though it’s most noticeable on meshes. It appears on the starter content meshes (Cube, etc), so I do not believe it’s caused by my mesh or UVs. I’ve been using this workflow for years without issue.

I only started getting these corrupted lightmaps once I moved from 4.15 to 4.24. Was there a significant update to Lightmass in between those builds?

There were a ton of updates to Lightmass between those versions. And it could’ve shown up as an issue despite you not experiencing it before with BSP or imported meshes. I’ve encountered it in one project, and not in another, and only was using starter content meshes. So, I think you could be limiting your perspective there in terms of troubleshooting. Not saying it’s what I referred to precisely, since it could be something else. But I’m thinking that it’s one way to narrow down the possible causes. Distance field shadows can apparently cause weird blob-like shadows due to the distance field being insufficient to completely render an accurate shadow, so the distance field representation of the object of which a shadow is being cast. Distance Field Resolution, in the Build settings of a mesh, increases the accuracy of the representation for the mesh’s shadow. You probably already know about that, though.

It could also be the shadow is not the shadow of the wall, but a less lit area of the corridor that is not fully processing the lighting. It’s just a guess, and probably isn’t what it is. I’m no expert, just trying to help.

I’ll look into the Distance Field shadows. I appreciate the help! It seems like an obscure problem because there aren’t many other posts about it. Luckily I have GPU Lightmass that I can use to get around it.

Thanks again

Troubleshooting is a neurotic process sometimes, especially with helpful information scattered around the Unreal web site and other sources. I also wouldn’t put it past it to be something simple…but that’s just another hypothetical.

Having the same problem. Using 4.24.3 version. Is this resolved with 4.25? Been trying to find something about this bug for the last three days, this is the only thread talking about it.