There’s a note inside the UE5 Documentation for Lumen…
Issues like this can be fixed by increasing the number of Cards used with Max Lumen Mesh Cards, but that may not solve all issues. Alternatively, breaking the mesh into less complex pieces can resolve these types of issues as well.
This is something I glossed over during my original reading of the topic. I put together a scene from existing assets and noticed at certain angles on these pillars I would get light bleeding as seen below.
No bleed at this angle, but at a more extreme one…
You can see the light on the pillar is bleeding out of the lips near the bottom. This is definitely because the mesh is large and complex and not in smaller modular form.
So upon a second reading I saw that and figured I should try their advice. So I made the pillar it’s own mesh.
Then I placed that pillar adjacent to the one with all the leakage and tried the same extreme angle.
Problem solved. So definitely a lesson learned for me, this is a big deal for accurate lighting and now I gotta rework the whole scene to see how it works with small modular pieces.