Problem with MegaLights

Development Rendering
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1

Hello everyone,

I was wondering if there is a solution to fix this “light circles”, they appears only when MegaLights are activated, there is 3 RectLights on the roof, right on the top of the screenshot.

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And this is the same screenshot without MegaLights

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Thanks a lot for help :slight_smile:

2

Interesting, I’ve never seen that artifact before. Is MegaLights using hardware ray-tracing or not?

3

Thank you for your answer!

Well ray tracing is activated in my project, but if there is a specific ray tracing parameter regarding MegaLigts I didn’t found it.

4

It will use RT automatically, I just can’t think of any reason those artifacts would be present. What does the path tracer viewmode look like?

5

Yes thanks for the information, I’ve indeed seen that MegaLights doesn’t work without RT.

This is the result without MegaLights, PathTracing ON:

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And with MegaLights, PathTracing ON:

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I see no differences, so even didn’t know if MegaLigts have any effects with PathTracing ON.

Btw just for your information, on the left of this two screenshots I’ve removed some blue niagara effects, because in PathTracing they was making all the scene illuminated with blue light.

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But there is no differences if I also deactivated them with Lumen regarding the artifacts.

6

Little up here :slight_smile:
The problem still persists in 5.5.1

7

No idea what’s happening, but I would be curious to investigate if you can share some small repro.

8

Hello @Krzysztof.N thanks a lot for your answer and sry for my late response!

Amazing thank you, I’ll take some time with pleasure in order to to that, I think this week-end.
Just to be sure, if I understand well you want me to share a copy scene of the project, that’s right?

9

To save time:

Yes, you can describe some reproductable steps, to get the same effect, or you can share (privately with him) a ‘proof’ project. Better if you previosly clean the project as much as you can, to keep only the neccessary conflictive assets, taking part when causing the issue.

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10

Thank you @Miguel1900 for the details :slight_smile:

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11

Yeah, likely I don’t need your entire scene, just some repro steps or maybe some small project with one floor mesh, a light and PPV volume. Basically some way to reproduce that issue on my end, as I haven’t encountered anything like that before.

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12

Sorry to reply to an older post like this, but given that this topic never reached a resolution, and I personally couldn’t find any other threads on the matter - did this ever get addressed on your end? I’m hitting this problem on my project with UE5.7.1.

13

You could try to lower r.MegaLights.MinSampleWeight, that likely would fix it. Through ideally I would like to get my hands on a repro, so I can investigate and fix it properly.

This threshold is exposure relative, so I wonder if this is something with exposure setup? Like local exposure or exposure bias curves?

14

Adjusting r.MegaLights.MinSampleWeight to a lower value definitely fixed this, yes. I actually managed to get you a minimal repro, with just a plane, point light, fog and PPV. I’ve attached the archive (made with the binary UE5.7.1).

Things to note:

  • When I tried creating a new level using “Basic” and copying the light, fog and PPV - I could not replicate this. Only when I duplicated one of the maps where I was hitting this and basically removing everything but one of the problematic lights, keeping the PPV and fog was I able to get you a repro.
  • The repro project is completely blank in terms of project options, but since you mentioned exposure - my project has turned auto exposure from the project settings off, but having it on in the repro blank project makes no difference.
    • In the PPV I’ve set Metering Mode to Manual and have set Exposure Compensation to 11.

Hope I was able to help!

CircleIssueRepro.7z (4.5 MB)

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