Random lit and unlit duplicates (With pictures) Unreal 4.16preview


I am currently attempting to build lighting for my level, I have read the documentation about various approaches to lightmap unwrap.
I have also tested this on static and stationary light baking.

I have a library that was built as a quarter from various static meshes, then put into a blueprint and flipped.
To my understanding each duplicate would have its own unique lightmap in channel-1 but share a material in channel-0

The way I am thinking is that if there was an error with my lightmapping then surely it would happen to every quarter section blueprint of the library.

But it does not. It happens to just one of them where it is unlit and popping.

I also receive a couple of errors from other meshes where it says lightmap UVs are overlapped when they definitely are not (I made custom lightmaps with plenty of padding for the most part contiguous)

I have triple checked all the static mesh lightmap index assignments.

I really don’t know what is going on. Every day the “overlapping light map uv” error seems to randomly choose different meshes to alert me about, the next day their UVs are apparently fine.


So just 1 of the balconies disregards lighting/shading.

Please save my sanity.

Kind Regards


If no one knows and this is a new oddity then please reply with that to help my sanity also :smiley:
Thanking you muchly.

Check your Lightmap resolution. It may be very low, so it may look like random light and dark spots.
You can see whole scene Lightmap density by going to menu where “Unlit” is written on your first screenshot, then “Optimisation Viewmodes” -> “Lightmap Density” or just press Alt+0.
If your scene looks very blue, then it is definitely resolution problem and you have to increase it on your meshes, until scene become more greenish it that view mode.

Thank you for your response Druha,

I will try it out at the next available moment and post my findings to potentially help others.

If it is this, I do wonder why it would only affect one of the instances. So weird.