emissive material creates flickering lighting artifacts

[123SarahharaS321 (Sarah)]

Hi
In my current scene (UE 5.2.1) i have several candles which use an emissive material mapped onto a plane for the flame of the candle.
For some reason they create flickering noise light artifacts on surrounding objects that should be way out of their influence radius. Limiting the emissive strength of the material barely helps, which has me believing that i am missing some kind of other aspect of this problem.
Any help appreciated!

[SupportiveEntity]

Hey there @123SarahharaS321! Welcome back to the community! So the flickering you’re seeing is Lumen trying to find a good final gather solution. This will continue occurring on lower settings often. If you’re doing a solid render this thread here can help (it can also help for game settings but it’s mostly for non real time rendering)

UE5.0 flickering shadow (lumen?)

[flickering shadows 180822] https://vimeo.com/oviantales/download/741366208/1971e73821 Hello everyone I tried to resolve this problem for an entire week and I even if I found some tracks and clues on the web, I could not be able to resolve this shadow flikering issue. Any idea ? Every light in the scene is movable. I tried to enable Distance Field Shadows on every lights, enter r.Lumen.Reflections.HierarchicalScreenTraces.MaxIterations 4, I also switched from Virtual Shadow Ma…

Other’s have stated that increasing final gather settings inside your post processing and disabling Temporal AA in project settings could alleviate some of the flicker.

[Arkiras]

You cannot light a scene with small emissives and expect good results, you must use actor lightsources (point/spot/rect)

UE5 Light Material Flickering issue

You are probably going to have to lower the emissive intensity of your material or increase the brightness of your light. 1 candela is extremely dim… You may not be able to get rid of it entirely as this is just the nature of having small bright emissives in your scene, not enough of Lumens rays will hit the emissive surface and so it will not converge to a stable result.

[123SarahharaS321 (Sarah)]

Disabling Temporal AA and changing the anti aliasing method has indeed helped reduce the flickering, although not completely gotten rid of it.
For now i am opting to instead lower the emission strength significantly and use bloom in the post process volume for a similar visual effect.

[SupportiveEntity]

Glad it helped! Also during a final build without preview lighting the flicker will definitely be lessened as well. Though I do agree with Ark the living legend above as emissive lighting is great, but can be a bit finicky in situations especially for realtime applications. Increasing final gathering can also help a bit, but it will come with a solid performance hit in most cases.

[123SarahharaS321 (Sarah)]

I do have several other lights in the scene, i disabled them to show the artifacts in the screenshot more clearly

[Arkiras]

Might be this bug then. This is specific to Lumen when using TSR as the antialiasing method in 5.2 and earlier. It should be fixed in 5.3, if that’s the problem.

[123SarahharaS321 (Sarah)]

I am rather certain that youre correct! Good to know that it will be fixed soon and thank you for the help