Is there a way to disable emissive contribution from a static mesh in lumen… it really does look terrible… and if i have a light with a spot light on it i really dont need the added emissive.
This is what they spent years working on, that’s what global illumination is, bounced lighting 
If you don’t want it, you can just turn lumen off.
Then they wasted years of their life. lol…
But in all seriousness… lumen is great, but the blobby artifacts from emissive materials… look terrible. I want realtime GI, but i don’t need it for a small table lamp emissive texture…
Main issue is when i try to light everthing with real world lighting units and have to crank up the emissive material to match it get the correct bloom and everything to look right. The problem is the emissive material contributes too much when i already have a spot light in the area. Plus… most of the time small object with emissive materials look terrible in lumen.
Plus don’t comment on a forum post if you don’t have a solution. This is a problem.
Currently emissive materials use candelas/m² … though im not sure if thats even true… doesn’t look quite right.
I can just leave you hanging next time, if you like 
There is no answer to this, at the moment. Hardware ray tracing may help…
Static lighting looks amazing, but takes an hour to build. Lumen is trying to approximate this EVERY FRAME, it’s no wonder it looks blobby.
thats the thing you are wrong…
Already in my research im finding that r.Lumen.ScreenProbeGather.ScreenTraces 0 helps a great deal… and … unchecking “affect dynamic indirect lighting” on a static mesh also helps.
Not a perfect solution but im looking for more answers and options… so please don’t comment on things when you don’t know what you are talking about.
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Perhaps you could grace us with your superior knowledge when you’re done. Because someone posts just about every week with this issue, and nobody EVER comes back with a solution that demonstrably works…
i think i just did… what i just said demonstrably works. Though r.Lumen.ScreenProbeGather.ScreenTraces 0 doesnt always look as good… like using that makes light not hit the edges of windows for fake interior emissives…
Im not sure exactly what that does.
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I still have blobbiness
( nothing is moving here )
There is a tuning guide ( as you’ve no doubt seen )
Tweaking any options that are not already on cinematic, doesn’t seem to do anything 
I appreciate the doc! ill be going through this. Also on yours… check lumen reflection quality… up that way up and see what happens. That looks more like a reflection problem then a GI problem on that case. I could be wrong.
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Lumen has several kinds of noise but emissives in particular can cause two: Indirect diffuse lighting noise, and noise in specular reflections on semi-rough surfaces. What @ClockworkOcean posted above is specular reflection noise.
In both cases you should not be relying at all on emissive objects to light the scene, if they are overpowering your actor lightsources then you should be lowering the emissive intensity.
You shouldn’t be trying to exclude meshes from Lumen entirely because it means you will not get any reflection from them. If you need to exclude a surface completely from lumen my advice would be to break the emissive section off into its own mesh and give it a translucent material. Translucency is ignored by Lumen in 5.3+. This will allow the mesh to remain on screen, at full intensity, without affecting the lighting, and without having to disable screen traces.
Again though… this means you will have no reflection for the emissive surface. That might be fine for something like a light bulb that you are augmenting with a spotlight. Because the specular highlight for actor lightsources is just computed directly by the shader without having to trace rays into the scene.
Unfortunately this won’t completely clean up the noise in semi-rough scene reflections, just the specular highlight. Meaning it’s not likely to fix what @ClockworkOcean posted above, since it is primarily reflecting the scene. To deal with the scene reflections your best option right now is to use the tonemap strength cvar to clamp the reflection intensity: r.Lumen.Reflections.ScreenSpaceReconstruction.TonemapStrength 1
This will make reflections less intense, but it typically reduces the noise significantly:
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the problem with lowering the emissive intensity is that they no longer behave appropriately with bloom. But very good information either way.
Frankly I see this as a non-issue, but as I said you if you really need to do this then my advice is to break the emissive section off into a translucent material.
Doing it your way (disabling screen traces and setting the mesh to not-affect DF lighting) works, but the cost/benefit ratio is really bad in most cases, just my opinion though.
but translucent does not support nanite. Nore does it occlude for nanite. Also how does my way hurt cost?
also what do screen traces actually do?
That’s true but also… who cares? Does your emissive surface have millions of triangles?
Screen traces provide most of the high detail indirect shadowing and GI, especially for small objects because they are aggressively culled by Lumens surface cache and aren’t big enough to be well represented by the global distance field. If you have a pretty simple scene or a lot of high frequency textures that will mask artifacts then it may not be as big an issue.
Screen traces also provide pretty much all distant GI and GI from skeletal meshes, decals, geometry caches, and anything else that can’t be represented by distance fields.
Any idea what the check mark “use as emissive light source” does? Looks like things get brighter when u check it on… and look worse… im just curious.
2 things also to add…
real time lights… unfortunately dont show up in your reflections unless that area is lit by that light… so small radius… or for spot light if u look at it from the side and not via the spot shining off the spot light… the reflection of the light disappears…
But aside from that… the other reason to use nanite on everything is virtual shadow maps behave better with nanite from what i hear.
my other dilema is for a day and night cycle … ev100- 4 at night and ev100- 14 at day… the emissive values must be very high to be able to make it look like it would in real life…and unfortunately in doing so they contribute to much to the environment makign it look terrible
The attached setting is a real life camera… ev100 - 14 daytime, ev100- 4 night time…
The goal is to replicate this in unreal engine for day night cycle… I have done so successfully with real world units and turning bloom way down.
The problem is now lumen taking too much contribution from the emissive… and making ugly lighting…
Setting it to translucent and non lumen/nanite seems terrible for performance and id rather stay away from that. Plus the emissive is maked into a pbr texture for what part should light up.
It prevents the surface cache from culling that actor. It’s really primarily relevant if you are using hardware raytracing, because in software raytracing mode the actor will still be culled by the global distance field scene.
No idea what you are trying to say here
It’s an emissive surface, I imagine it is probably not casting a shadow. This is only a concern for shadow casting geometry.
I have no idea how you could possibly have come to this conclusion. Assuming you are only splitting off the emissive surfaces like I told you, it should make virtually no difference what so ever.
You can do as you please, it’s your project.