Lumen GI and Reflections feedback thread

Already reported a year ago, unfortunately. But, at least, they added to the TODO list for 5.5 (now moved to 5.6…)

@Krzysztof.N , I have noticed an issue with Packed Level Actors regarding AO, GI contribution or both, I would say.

Unfortunately I can’t test it now in UE5.5 as my main PC GPU is in a RMA process. But in 5.3 in my laptop, I have noticed this:

Cube directly in scene:

That same cube converted to PLA:

(All my floor rocks must be suffering the same, unfortunately, as they are all in a PLA).

The repro is really easy, jusy place an actor in scene and create/convert to PLA. Please, could yo confirm if it still exists in 5.5 and/or provide a fix, maybe? It looks like an important effect to get lost.

Thank you very much

EDIT:
Looks mainly a non-GI response, with and without HW RT. PLA vs normal:

Basic test project: Dropbox

EDIT:
Ok, some inquiries here! (Remember, this is 5.3, I will be able to confirm in 5.5 in one week, if you don’t do it earlier):

  • Non-nanite meshes will be packed in PLAs as HISMs, while Nanite ones will be packed as ISMs
  • HISMs won’t bounce lighting if they are non-nanite, but will do, if they were ISMs (so, why package them as HISMs?)
  • But even being ISMs, it also seems like non-nanite ISMs won’t cause ambient occlusion, additionally. Also if being HISMs, which seems the worst case.

In Lumen scene is very easy to see the differencies in surfaces debug colors.

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