Lumen quality advice for film

Development Rendering
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I am starting a short film project with Unreal Engine 5 as I am keen to use both Lumen and Nanite but I am becoming a bit dismayed but what I perceive as the low(ish) quality of Lumen.

I just cannot seem to get rid of the grainy noise Lumen appears to be producing and I seem to be having a terrible time with spotlights.
My major issues are:

  1. Lumen just seems to be hit and miss with general quality even with point lights
  2. Spot lights seem to be screenspace GI only. As soon as I face the camera slightly away from a spotlight the GI just goes black.
  3. To combat the spotlight issue I decided to use emissive “lights” but the Lumen output is all mottled and really not good quality.

I have seen Youtube videos regarding emissive materials and the poor Lumen quality but surely I can get nice clean results and surely I can get well behaved Spotlights.

As my project will be rendered out as a short film I don’t particularily care about FPS, I only care about quality. I even tried to use Pathtracer and I found produced great quality (slowly)… but… doesn’t support Groom hair which I am using and volumetric fog :frowning:

Can anyone suggest any specific cvars I might need or any other settings that can solve the issues I am having. I am loving the near realtime workflow, having a great time with realtime hair strands and my skin and Nanite meshes look great… just the lighting… argh…

Appreciate any advice.
PS. I am using raytracing with Lumen and I thought that might solve the spotlight issue and mottling but no :frowning:
PC Specs (if it helps with quality settings)
Intel i9
128GB Ram
Nvidia 3090RTX

Thanks in advance :slight_smile:

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While I can see the appeal of this stuff for your purposes, truthfully I just don’t think it’s there yet despite the way they market it. It doesn’t yet cover all the bases for real-time games, where we are willing/expect to deal with visual trade offs for performance.

There are just too many things, like groom hair being only affected by certain lighting situations and looking really weird in others, foliage issues etc, that need to be worked out before you’re going to get anything comparable to an offline renderer - for games projects we look at the overall game world and deal with minor stuff because the lighting being iffy in a certain spot is relatively minor over all. But for you, iffy lighting can ruin an entire shot or sequence of shots, and thus a large part of your overall project.

And of course, the eternal caveat; it’s not a final release and can’t be expected to work perfectly in all cases etc etc.

If you’re going to pursue it anyway though, the best advice I can give is the following.

Number one, make sure you have read the Lumen technical details page and are building your environments in exactly the way it expects given the way it processes and reads the scene.

Two, specifically on the spotlight issue although I haven’t tried one yet; if it is not working right, could you try a point light with a geometry shroud to make a “real” spotlight? It’s expensive, but if frame rate isn’t a major concern…

Three, skip Lumen for the final render and enable hardware ray tracing support and RTGI brute force method with cranked settings; although this may lead to problems with nanite meshes and you may have to use regular static meshes instead at a frame rate that would be unnacceptable for games, but may work alright in your use case.

Lumen is great where it works, but it’s unfinished and is still a performance compromise aimed at real time devs who can’t go around rampantly tracing rays without it heading into slideshow territory. You might be able to make use of features we have to back away from to get what you want.

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As far as I understand it (which, admittedly, isn’t very far), Lumen is not technically more “correct” than just using raytracing. If you are talking about Film, raytracing will still be superior, save in that Lumen can give you look dev results much faster for basic setup.

That said, your specific problem I think can be handled by just increasing the lumen settings, which by default have a fairly low ray count. There are several youtube videos that discuss how to remove the “mottling” you are talking about.

Additionally, I believe that rect lights are superior to spotlights in most circumstances. Is there any specific reason you have to use spotlights?

1 Like
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Wait until it is actually released to form a conclusion on whether or not it would be suitable for your needs, would be my advice.

UE5 is not released yet, it is in early access. Practically all of its features are unfinished.

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@dragonlordsd I actually had not thought about rect lights instead of spotlights, I completely disrearded them for no good reason.
Thanks for the advice I’ll give them a go now.

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If lighting or reflections are only happening in screen space, it normally means you don’t have proper distance fields setup for your scene. Use the Lumen scene visualization under show options and make sure you have distance fields enabled on meshes.

Also make sure the distance fields are accurate to your scene.

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Hi bro please use “Movie render queue” for rendering and increase the AA samples

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Thanks @anoopkalpaka definitely increasing AA samples in the render queue makes a huge quality difference.
My biggest issue is the mottley (is that the word) noise that appears on walls etc with Lumen.
I have managed to improve shadow and reflection quality with some of the advice in here but the mottled noise still occurs when playing the sequence (or recording).

I’m not sure Distance Field resolution changes have much effect as I am using Hardware Raytracing in Lumen and I think they are really only in effect if using the software tracing. Increasing their resolution seemed to make no difference.

If I crank the brightness of the scene up the mottled noise goes alway but this is a semi diim scene in a basement and with a few rect lights used as spotlights to light the area the mottled noise is very noticable.

I was hoping there were some console varable settings for Lumen that I could change to increase the number of samples or something to remove the noise but so far have come up with nothing other than ones that have definitely improved shadow blending and sharpness.