Noise in Cel Shade Post process effect with Lumen

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I am seeking some direction resolving an issue.
I am currently trying to make a cel shader post process work in my game but ive ran into an issue with some poise in the shadows.
I’ve been mucking around with every setting i could think of and turned off AO as i dont super need it in my cel shade bands, but the problem persists.

In trouble shooting i confirmed that the mask isn’t adding the shadow and seems to come in when i add the scene back in through post process0.

When i played with lighting setting in the post process value i found that the noise disappears when lumen is removed.

I really like lumen as it was one of the selling points of me learning unreal 5 versus 4.

Is there any way to have lumen’s default source based lighting profile changed to utilize the same curve my post process volume is? or possible to eliminate the noice while still using Lumen?

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Bumping this because I also have this issue when doing Post Processing Cel-shading.

Has any solution been found yet?

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Bumping this again, still no fix? @Evan_Axel

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Answer was in the original post: Don’t use Lumen.

Also applies to DFAO and any other effect that is not temporally stable. There’s no way to fix this.

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I see… is there a temporally stable GI? Or way that I could create a similar appearance? It just seems too cheap without Lumen.

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Baked lighting would work, another option would be ambient cubemaps, otherwise you can fake GI by placing additional lightsources in areas that should be lit up by bounce lighting.

You may want to watch this video by Tango Gameworks on how they lit Hi-Fi Rush (in UE4, so no Lumen)

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This person did:

https://www.reddit.com/r/unrealengine/comments/yss6iz/post_process_toon_colours_celshading_and_outlines/

So it is technically possible, it’s just a matter of figuring out the best method that works.

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I can’t conclude much from this video:

  1. First half is the easiest possible use case, exterior direct lighting with little no no bounce light what so ever.
  2. Second half shows smearing in the feet (23s mark, probably due to disocclusion) so this is clearly not perfectly stable.
  3. He’s using a single band shadow which is the easiest to deal with and is not what the OP posted about.

Regardless, you’re welcome to try but if I were you I would not be so optimistic. Even if you could get it to work, spending upwards of 4ms on Lumen just to crush the detail out of it seems like a complete waste of performance.

Edit: If you’d like some advice:

  1. Disable Screen Traces and turn off Lumen’s short range AO. Short range AO will produce a grainy look and Screen Traces tend to produce more noise because they can pick up smaller details than tracing through the Lumen scene. Turning off screen traces will also allow you to have better control over the Lumen scene so you can remove problem causing meshes with fewer issues.
  2. Avoid reflective materials.
  3. Avoid emissive materials unless they’re translucent.
  4. Keep windows large and don’t rely entirely on bounce lighting to illuminate the scene.