Flickering in a mirror UE 5.5

[looore91]

Hi everyone,

I’m working on an Archviz project in UE 5.5 to produce some videos. While the overall quality of the images and animations meets my expectations, I am encountering some issues with reflections in mirrors.

NewLevelSequence16 2

As shown in the video, particularly in darker areas, there are blotches and flickering.

I achieved some improvements by increasing the “Reflection Bounce” value in the Post Process Volume from 1 to 2. However, the flickering persists, and further increasing the value does not seem to yield additional benefits.

Do you have any recommendations on which parameters I should adjust to address this issue?

Additionally, is it possible to use Planar Reflection Screen in UE 5.5?

Thank you in advance for your assistance!

[Ivan3z]

Try this… i had a similar problem once… Maybe it work for you too

500×500 2.84 KB

Ok… in my case i think this is the best solution (for now) No noise and good performance!! Simply use “NONE” as the global illumination method. [Captura de pantalla 2024-06-01 124224] The downside is that some shadows look very strange. A better solution is welcome!! Thank you so much!! EDITED This fixed everything: Noise, shadows and performance. [Captura de pantalla 2024-06-01 131712]

[looore91]

Hi @Ivan3z thanks for the suggestion!
I tried it, but the result is what you see in the video.

Flickering in a mirror UE 5.5

[Ivan3z]

It is for a architecture project?

Maybe you can try this…

Fix Lumen Light Flickering in Unreal Engine 5.3 Tutorial

I don’t like this solution because i makeing a game and the performance drops a lot…
but maybe for a architecture project it does not matter…

Anyway in a mirror you will have not a perfect reflection (like a real mirror)
Not if you don’t have a mega-super graphics cart… even so maybe you will have not a perfect reflection.

Real-time rendering has many limitations and reflections are one of them.

[looore91]

Hi @Ivan3z , thanks again for the suggestion.
Yes in this case it’s an architecture project and I wouldn’t mind taking longer time in rendering the frames if in the end the video turns out smooth and without flickering.

I knew the video you linked and I had tried increasing the value of “Final Gather Quality”, but still in the mirrors remain that annoying flickering. Any other ideas?

[Ivan3z]

What about a metallic grey material? It’s not a mirror but it simulates one.

[3dRaven]

Yes planar reflections seem to be possible in 5.5

Planar Reflections in Unreal Engine | Unreal Engine 5.5 Documentation | Epic...

[looore91]

Hi, I modified the mirror material, reducing the Metallic to 0.95 and increasing the Roughness to 0.1. This way the reflections will be less sharp but at least I can limit the flickering.

Here you can see the result of the animation:

NewLevelSequence12 2 7

If you have any other suggestions, I would be happy to do more tests to improve it.

Thank you all!

[Ivan3z]

No tengo mas ideas @looore91
Solo conozco esas dos formas de hace espejos.
La cuestión es si tu estás contento con el resultado.
Definitivamente para un juego el material es la solución mas barata.
Para cinemáticas “Planar Reflection” es lo mas realista pero también lo mas caro y sin un buen hardware no vas a tener buenos resultados.

Un placer ayudarte!!
Saludos!!

[3dRaven]

You could go full old school and just duplicate the room on the other side just mirrored. Just add in a glass panel where the mirror is to get light interaction.

[Ivan3z]

Este material es “Cristal” transparente… por si decides duplicar la habiltacion tal y como propone 3dRaven

[Arkiras]

Please see this post:

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So I finally found some settings that’ll make the Archvis crowd stop complaining about noise under indirect light, especially in reflections. Maybe I’m late to the party here and someone else found this, but here it is: Default: r.LumenScene.Radiosity.Temporal.MaxFramesAccumulated 4 r.LumenScene.Radiosity.HemisphereProbeResolution 4 [image] Default (Low) Probe Resolution, Very High Temporal Count: r.LumenScene.Radiosity.Temporal.MaxFramesAccumulated 32 r.LumenScene.Radiosity.HemispherePr…

@looore91

Additionally, is it possible to use Planar Reflection Screen in UE 5.5?

Not with Lumen

[looore91]

Hi everyone and thank you very much for your advice.

I have done several tests in this time and finally got better results with this configuration:

• Machine: i5-12400F, RTX 4060, 16 GB

• The console variables in the export settings:
  r.LumenScene.Radiosity.Temporal.MaxFramesAccumulated 32
r.LumenScene.Radiosity.HemisphereProbeResolution 4

• Post processing box settings:
  Lumen Scene Lighting Quality 8
  Lumen Scene Detail 4
  Final Gather Quality 2
  Quality (Lumen Reflection) 2
  High Quality Translucency Reflections Yes
  Max Reflection Bounces 4
  Max Refraction Bounces 4

• Mirror material:
  Color Base B8D9D9FF (slightly blue/green, I think it adds some realism)
  Metallic 1
  Roughness 0.04 (a little bit of roughness helps with distant details that don’t reflect perfectly)

Surely I could optimize the parameters even more but it looks good to me compared to the beginning. This is the result:

NewLevelSequence12 2 14

I will also keep the trick to duplicate the whole room and apply a transparent material in the mirror, in case I want to render the scene even more accurately.

I will continue to do more testing and keep you updated!

[Ivan3z]

It look great.
Thank for sharing your config!!