Going nuts - Lightmass shading errors on modular parts

Hi guys and hello to the UE4 developers!

I love really UE4 and enjoy working with it, but this is really bothering me.


If I´ve got an interior scenery with modular wall pieces I get different shading on some parts. I´m not talking about seams, just a totally different shading color. I know about the problem and I´ve tried all workarounds I could find on the internet and sometimes it helps, but sometimes I spend just too much time trying to find the right adjustment for a simple scene. The problem is more obvious when there is very little light in the scene (i.e. just one window) and I pump up the bounces to get GI illuminating the room.

Please EPIC, can´t you do some kind of magic, i.e. a grouping function to tell lightmass to render these grouped pieces on one thread to avoid light shading errors. I know I´ve talked about this a couple of times, but this is really getting me frustrated. Sure it works in the end, but the amount of time I have to spend to get rid of these errors is just to much.

Some kind of selecting the objects I want to bake would also be great when I don´t want to spend time to bake the whole scene.

Perhaps a UE4-guy could write a comment on this?

Best regards,

Hi ForGobbler,

  1. With the Modular pieces, it’s best not to overly modularize where your planar surfaces will be lined up. If you want to use this type of method, it would be better to use other geometry to hide the seams, adjust some of the Lightmass settings to get better results, and/or rework your lightmaps to reduce this artifact. I’m sure you’re familiar with most of these settings. At the moment, I’m not aware of any plans to change how this works, at least not in the near future.

  2. Selected Light Builds, This has already been submitted as a feature request with UE-10034, but this is backlogged. There has been some interest in bringing this one back and it may be added in the future, but there is no time frame or a guarantee this will be added to the engine.

Thank you!


Thank you very much, Tim!

Hi Tim,

Our team also has issues with these modular pieces. It’s like the light is calculated on a different thread different from the other modular pieces around them.

Is there an example out their of how this has been overcome successfully? Replacing the Geometry kinda defeats the point of being Modular right? Especially if people release Hyper Modular packs.

It would be nice to see a scene that suffers with this problem and seeing the tweaks people use to getting it look perfect. (cutting out the light build times in the tut)

I would +1 a system that you could group certain Meshes to ensure they all got lighting built the same way/same thread.