Lightmap Resolution questions

Hi guys,

I’m trying to understand why my build times have recently skyrocketed for my scene

In terms of lightmap resolutions. The highest single lightmap resolution I have is for 3 objects that are 1024, the rest are 512 or lower.

Now when I go to the statistics window and sort by lightmap/shadow resolution. I see that my top object has a lightmap resolution of 5,504, but it is made up of 86 seperate objects. (To clarify, these are individual static meshes referencing a single mesh, not static mesh instances.) Does Unreal create one giant 5,504px lightmap for these? Or does it generate 86 different 64 pixel lightmap textures? Could this be the cause for my long build times? I am using rafael’s .ini settings and rather high quality settings so it’s entirely possible it’s just my fault :P, but I just wanted to double check.


There are many things that can affect light build times, number of objects, lightmap resolution, and render settings. After it generates lightmaps it will combine them into texture atlases but the atlas will have a power of 2 resolution.

I understand. But there’s no difference between having 10 different objects at LM Res 64 and 10 objects that share the same mesh but are still at LM RES 64, right? They don’t like all of a sudden take longer because its building a bigger Lightmap right? I guess I ask because I heard something about lightmaps can only be done one per thread, so if you have a HUGE lightmap, it can increase build times substantially because only a single thread can work on it, so I’m just making sure I dont have like a 5500 px lightmap by accident or something. (Correct me if I’m wrong on that)


No, there’s no difference between 10 unique objects and 10 copies. The only difference is that it will keep one of the meshes in memory if you use it multiple times but each copy uses a unique lightmap.