Extreme Lumen ghosting issue

Hi everyone, I’ve been working with Lumen in UE5.2 for a while now and I’m happy with the overall lighting quality, I am however getting some extreme ghosting when moving around the level (first-person, both at normal walking speeds and while sprinting).

I’ve tried several trouble-shooting methods from all over the forum but without any improvements to this effect - any help or advice would be greatly appreciated!


Trouble-shooting info:

  • Turning off Lumen removes the ghosting effect so it has to be Lumen related
  • Starting a clean first-person template project comes with this issue out of the box, it’s more apparent on brighter materials and wherever there is more contrast between faces
  • Multiple play-testers on various systems have mentioned seeing the effect
  • Motion blur is turned off
  • I’ve tried every type of AA or turning it off entirely without effect
  • I’ve tried all the Lumen quality settings (final gather, update speed etc.) without effect
  • I’ve tried removing large emissive materials without effect
  • I’m using Shader Model 5

I’ve been looking into the Mesh Distance Fields and Global Distance Fields and their respective visualization views, but I’m not sure I understand how to interpret them:



Do these look healthy? Smaller meshes (25x25) are completely invisible in my MDF view. I’ve tried increasing the Distance Field Resolution Scales to the max but that doesn’t help much. Are MDF’s only important for the overall level structure (walls, floors etc.)?

I could really use some guidance or help to resolve this issue.

Thanks,
-Tim

Update after doing some more trouble-shooting:

Most of my meshes did not have proper Mesh Distance Fields / Global Distance Fields because the material was set to double-sided. Some meshes did not even show up or have any Mesh Distance Fields, this was because “Affect Distance Field Lighting” was unticked on the static mesh inside of the blueprint.

I’m sharing my process here in case anyone else needs it in the future.

The ghosting issue is still unresolved. Any help or insight would be appreciated.


It could be screen traces. Try and disable them to see if things work any better.

r.lumen.reflections.screentraces 0
r.lumen.screenprobegather.screentraces 0

Thanks for the suggestion comlys, unfortunately disabling these did not affect the ghosting:

I’ve also tried lowering (from default value of 10 to 0) r.Lumen.ScreenProbeGather.Temporal.MaxFramesAccumulated but that just trades the ghosting effect for noise. Turning the value up to 50 greatly amplifies the effect.

Any other thoughts?

My only other thought is that it could be shadow artifacts. Are you using VSMs or RT shadows? You could try switching the shadow type.

I’m in 5.3 and I have a similar (or maybe the same) problem. In regular objects, there is a slight ghosting effect, but in widgets in world space it is completely unplayable. And it looks more like a shadow problem, but I tried enabling ray traced shadows and changing VSMs for normal shadow maps and nothing made a change. I did almost all of what you did (and I also tried disabling screen traces), and I got to the same conclusion.When disabling lumen the problem is gone. Does anybody have a fix for this?


With ray traced illumination or screen space and MSAA, the problem is completely gone. But it doesn’t look nice, I guess there’s no fix to stop lumen from making this ghosting effect, but is there a way to reduce it?