Yes, this was on 5.3. I should have noted that.
I’ll give 5.4 another go.
Yes, it’s actually fixed in 5.4 
Thanks for the heads up
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@Krzysztof.N I’m not sure if it’s still even being supported, but switching on lumen’s irradiance field gather in 5.4 instantly crashed my client, and has done so multiple times, opening different levels and with different lumen settings enabled beforehand. Is that lighting strategy considered abandoned at the moment?
Truthfully, I feel like it hasn’t worked since 5.0 or so, or at least that is the last time I remember it being usable (albeit low quality of course).
@Krzysztof.N or @Daniel_Wright I would like more information on this erratic behavior in 5.4 software Lumen’s AO(I’m positive it’s not short range AO). I haven’t experienced this in editor but haven’t used 5.4 Lumen very much and just wanted to see the quality in FN and I keeping finding this annoying glitch, (video is 4k which means it’s short, put the video on loop)
See how the AO disappeared. It kept happening repeatedly over and over in FN with high scalability.
Maybe you guys will immediately recognize the issue here idk, hope that’s not in the final released 5.4 version.
Let me know when or if you guys find or fix this this issue in the shaders.
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I like lumen a lot, but I’m having 2 issues.
Lumen is apparently using TAA to get rid of noise. This TAA is blurry in motion, especially on stylized low poly geometry. I can’t find an option to use 200% history screen percentage anywhere. This is essentially upscaling to 200% screen resolution and it’s the solution to TAA blur in motion. I have tried to set the final gather lighting update speed as low as possible to reduce the noise in a different way (with r.Lumen.ScreenProbeGather.Temporal.MaxFramesAccumulated=3 to get less smoothing and blur) but I cannot set it lower than 0.5. I don’t know if it’s possible to go lower at all, but it would certainly help
When I use foliage paint, procedural foliage or PCG with regular LOD meshes, all instances are black in the lumen scene. They can only block the landscape and skylight as a result, no indirect lighting or illuminated reflections. Nanite does not have this problem, but it makes my 3070 quite a bit slower than regular LODs. Static mesh actors are correctly illuminated in the lumen scene as well, but it’s not practical to drag every object in the scene by hand. I don’t know if the problem can be solved for regular meshes, but I think it should be possible to bake instanced foliage into a series of static mesh actors. Only for objects that are bigger than a certain size, to keep the amount of actors as low as sufficient
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I forgot to mention one issue. Physically accurate indirect lighting is a little hard to see. That’s why I often brighten it up with the indirect lighting intensity property of the directional light. The problem is that it brightens the reflections as well, which does not look good at all. I think the reflection brightness needs to be decoupled from the indirect lighting intensity. The screen traced reflections are unaffected though, I’m talking about the reflections of off screen objects
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Lumen uses temporal accumulation from
r.Lumen.ScreenProbeGather.Temporal.MaxFramesAccumulated which at least doesn’t blur the whole screen like TAA(and TSR cost too much or fuzzes-ups motion).
But yeah, I’ve spoken about how raising MaxFramesAccumulated above 10(default, still a lot of noise) causes the light to smear, so at the moment, it forces you to use hybrid temporal smoothing and that really sucks becuase I’ve seen some pretty dependable GI that doesn’t do this.
At this point I really want Lumen to incorporate a bakeable aspects, the volumetric lightmaps are so broken with so much leaking and memory usage. And Lumen also seems to be wasting a lot of performance on trying to figure out and re-iterate on the scene that are static even if everything is lowered to the slowest possible update. Like the noise and sporadicness could be fixed with bakeable probes.
Lumens supersamped probes is a really smart way to go about faking multiple diffuse path traced rays, but what would be more appropriate for most static games with moving lighting would be something a combination of The Divisions GI which runs way better than Lumen. Allowing us to bake supersampled probes could include super sampled world normal buffers to prevent leaking as well as depth functions to probes closest to geometry like the ones used in EA’s solution..
I guessing for a solution like this, we would need two kinds of bakeable volumes. One for indoors and one for outdoors. Indoor volumes would need the mark probes with a hierarchy in this order light source is visible, direct light is only visible, and neither visible. Then for basic dynamicism, those would only have to trace if an object is occluding the probes “view” of the light source or direct light and di probes under a lower hierarchy based on what percent of higher hierarchy probes are being occluded from whatever their tag was.
This wouldn’t be too bad to work with if each volume could have an array of profiles we could blend between and access via blueprints. Atm Lumen seems to cater to dynamic worlds, with dynamic lights, where at most games using unreal are static worlds with dynamic lights.
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This only came in a day or so ago, and as UE 5.4 just released I don’t exactly have time to rebuild UE and test it, but I’d be very curious to see what the resolve of hit lighting GI looks like. Does it mean the surface cache itself is just discarded, or only read on the second bounce?
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This looks very interesting. I am also curious how this behaves in terms of noise and update speed.
GI currently can be painfully slow to update. Not relevant in many use cases, but if fast updates are required it’s almost unusable at the moment.
Good to see Lumen is pushing further in both directions though. Down is terms of scalability and up in performance.
thx for the update. i’ll rebuild it. will test and throw some pictures in approximately 3.5 hours. hmm
Performance is definitely one of the big questions for me- Surface Cache GI with hit lighting reflections already got incredibly close to PT reference in my testing, so I’m curious in terms of what content could really benefit from this system in a large way. Besides emissives, I do remember testing a herringbone-style wall mesh that significantly broke lumen GI, with massive amounts of lost energy compared to PT.
Maybe it will drastically reduce noise, patches and weird AO, beside more general accuracy.
okay. i get it. raytraced direct makes a clean sun shadow in the highrise “windows”. reflections. the skylight was already good but it was noisy. also… in the prior test “renders” i intentionally shot the spotlight into the mirror surface to portrait lumen gi reflecting onto the ground. i reckon in raytraced mode this is too direct (without multiple samples) and will not yield the spread the surface cache has.
and the emissive cubes in my test map look very stable, now. hmmhmm
nice. 
screen percentage is 100% btw. it’s not full blown maps but technically okay in screenspace. and runs cool.
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How well do the area shadows resolve in reflections? I’d struggle to believe that would make a large visual difference in most scenes, but I’m curious about the perf cost.
well… they don’t resolve. this would be rather expensive, i think. the directional light according to staff is a brute force xtra pass that mosdef is not represented in the reflection bvh. i dunno how the rect light is rendered. both do not smooth tho.
jsyk… the directional light is blown up to 90 source angle for the first hit and 90 source soft angle for the smooth reflection math. the rect light is visible. that’s what you’d get.
and the before…
(i wish the light bounce from the spot mirror would still be there in the main pass. it is reflected light but lumen handled that bounce pretty da*n well.)
nvm. it only shows up in lightingmode 2. btw… you should point your camera at a mirror and run thru the console variables. you’ll figure it out. the controls are nice. scene dependant tweaks can be made.
and a lil roast mode with possible puddles. i’m aware the ps5 gotta do that in 1440p at stable 30+ fps. or even more on the ps5 pro. i can see the development. yo…
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a minor inconveniance i noticed in this test map a couple of times. the “overcast” direct light, at certain backwards angles, throws a bunch of noise onto flat surfaces. not sure if this is mathematical or a content issue. cheap boxes are no good, i know.
also happens on the box i put infront of the rect light.
I was browsing through some cvars when I discovered something interesting. Looks like we might get RESTIR Lumen at some point. Trying to activate it will just black out the scene unfortunately.
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Hey guys! Great work on 5.4. Im trying to build stand-alone on the quest 3 and even with global clip plane enabled I can’t seem to adjust my setting to get the planar reflections to show up in both eyes. I’ve toggled the stereo view and multi view modes for multiple builds and tried adjusting the false eye offset, but it always seems to have a very similar result. Any suggested setting to get this working on a quest 3?
Since planar reflections aren’t a lumen technology, I’m not quite sure this is the right place for your question. That said, I don’t believe planar reflections are supported by VR? At least not in the documentation I’ve seen.
Hey, this tutorial will be of great help to improve satin materials reflections
I think this is the one of the worst lumen Tutorials I’ve seen so far. Extremely biasing the reflection ray intensities and then messing up the desired material roughness values to compensate for it is one of the worst ways to go about it.
You are essentially completely changing what the original material is supposed to represent just in order to remove artifacts caused by combination of the technological limitations and incorrect sampling settings.
In real world, if you do archviz and client tells you “the table is not supposed to be shiny polished wood, it’s supposed to be matt finish”, then you are screwed because as soon as you increase roughness again, you will lose reflections almost completely (due to the excessive reflection ray clamping), in which case client will again say “the table is not supposed to be completely rough finish, just a matt polish, but not glossy”.
The fact you dare to advertise paid courses called “elite renders academy” at the end of showcasing such poor, beginner understanding of Unreal’s renderer, it’s a cherry of cringe on top 
My response may sound unnecessarily harsh, but it really frustrates me when people with merely the most basic understanding of things immediately start their own paid courses and academies these days, because it feels like its scamming other beginners out of money, for low quality information, and beginners especially are usually running short on money. 
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