Lumen GI and Reflections feedback thread

Tried ‘r.Lumen.Reflections.ScreenSpaceReconstruction.TonemapStrength 1’
Worked great in some rough meshes but overall scene look poor. For archviz video it really helped me. I had to render twice the scene. One with default value of 0 and second one with value 1 and compose in post production. Its nice to have this workaround at least but it would be great to have some per object or per material solution that doesn´t affect entire scene. I dont know how difficult that would be to implement or if it´s possible at all but it´s a must for a lot of users. That being said, for architects like me, Lumen is a miracle using it in design early states and not only with finished products baking lights and unwrapping as we had to do in UE4. I´ve been working with Lumen since EA and the software its getting better an better. I understand the frustration that some users who need it for real time or games development are feeling, but In my opinion it´s fair to say that Epic are doing a great job even thought it is not fitting the needs of all users in its current state.
As some users said before it would be great to have a high quality switch for video in movie render queue. If we could have better mirror reflections and a workaround for noise in rough reflectionsm there will be no need for path tracer in 90% of scenes. It hard to deal with people like me who need quality and doesn´t care about performance and people who need performance for real time, I Know. Thanks for your work and for taking the time to answer forum users.

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For sure there are a bunch of things we could do. The current Lumen Reflections is designed around performance limitations of consoles, yet today’s PC GPU’s are massively faster and can afford much more work. We’re not scaling up past consoles, and we haven’t had time to work on that yet.

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I’ve seen the videos, they look amazing and it’s something we need to look into.

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Not at the moment. We’ve talked about it a lot, but there are some complications:

  • Requires extra Surface Cache atlases to store ShadingModelId, Opacity, SubsurfaceColor. Lumen is already using too much VRAM, and the Surface Cache atlases don’t resize based on your use (hardcoded 4k^2), so we’d have to optimize elsewhere before we could do that.
  • Trees (which the backface lighting would help) suffer from a bunch of other Surface Cache problems like missing coverage, so backface lighting is not the hardest thing that needs to be solved here.
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This looks like Ray Traced Shadows to me, not Lumen. You’re showing the lit viewport and not Lumen Scene, so the shadowing here is coming from Ray Traced Shadows, which it looks like aren’t skipping translucency properly. I don’t see how that could have been affected by the Lumen console variable. It’s something we need to fix for sure, I will do a test to reproduce and report it to someone who owns Ray Traced Shadows.

Lumen is so widely used now that we spend a lot of our time on internal and external support, rather than making forward progress. Every season of Fortnite brings new challenges (visual artifacts, performance regressions), then there are the many UEFN projects exposing Lumen artifacts, Special Projects teams within Epic having Lumen problems, the list goes on and on. Probably not what you wanted to hear, but…

Glossy reflection denoising is near the top of our team’s priority list, but it’s just hard to work on with all of our other requirements.

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Thanks, should be easy to fix.

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they look amazing and it’s something we need to look into.

For the love of God DO NOT. It does NOT look amazing in motion. Which tends to be in games?

It’s so blurry and smears in motion. We already have to deal with Lumen being temporally dependent

There is no logical sense to try to make blurry crap the standard for games. Epic games already did that with TAAU.

If you don’t think Temporal AA methods are bad go to r/f**taa.
You find most comparisons showing TAAU ruining motion/gameplay.

The biggest reason RR makes reflections better looking is because it more aggressively smears past frames on reflections. Which results in ruining everything else in motion such as NPCs and soon we’ll see third person smear like crazy.

We need common sense algorithms for games, not cinematics. Playing a path traced game at 720p makes no logical sense. We need actual performant visuals that actually play well with fast gameplay.

Stop falling for this cinematic crap.

Yes, we’re not scaling up as well as we should be able to. We do have higher quality settings that Lumen uses in MRQ (Cinematic scalability), but it still relies on screen traces / surface cache / radiance cache (which have their artifacts) and Lumen Reflections doesn’t scale up at all. Then there are the aliasing artifacts on small details that Lumen screen traces cause with AAMethod=None. And some things like Hit Lighting / multiple reflection bounces don’t get enabled automatically.

Thanks for your feedback, it’s on our minds.

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I honestly figured as much, at this point. With four major public revisions of lumen (E.A-5.3), I struggle to think of must-have featuresets that aren’t supported in some way. With larger codebases and interdependent systems, it makes sense that forward momentum would become slower. I know many people will be more than happy with bug fixes and performance improvements, and the new features can arrive when they may. I really appreciate you being on the forums and letting the community know what to expect, thank you.

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DLSS 3.5? In everything that I’ve seen, it looks like temporal resolve is significantly improved compared to, as NVIDIA puts it, hand-tuned denoisers. It certainly looks better than anything else I’ve ever seen.

Daniel Wright stated that bugfixes and performance improvements are currently top of the priority stack for lumen. How lumen can function without temporal accumulation is a question for the coding oracles.

Speaking from the AAA devs I’ve talked to who have shipped titles, I don’t think ‘common sense’ and ‘game algorithm’ ever go together in the same sentence. Games are built out of hacks and kludges and cringeworthy last-minute fixes to ship. They are anything but elegant, but they are what games are as an art form. If you don’t want to use the newest technologies, that’s more than fair, but the lumen team is doing the best they can, and I think it’s particularly kind of Daniel Wright to visit the forums and let us know what the progress looks like.

Unreal Engine is now a cinematic and movie creation tool as much as a game engine, and Epic has a responsibility to both userbases. I understand that you’re upset with the limitations of the technology you’re facing, but the rest of us are as well. Let’s just do our best to be polite, to the people and the forum that lets us do the work that we do.

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I was actually thinking less about foliage and more for materials like thin fabrics where you get very noticeable shadows you can use for shadow puppet effects or just to give mood to a scene, like tents, shoji doors. To some extent I suppose it can be worked around with emissives.

Anyway, thanks for taking the time to respond. I can appreciate that its a niche issue and there are much more pressing concerns to consider :slight_smile:

On the bug note as well:


Car paint in the city sample glows white when reflections are enabled with 2+ bounces and are out of screen-space.
!

The color appears completely white and doesn’t appear to be receiving any lighting at all, even as the wheel is clearly receiving direct lighting from that point light. I’m guessing some issue with the car paint shading model?

Importantly however, it’s not all cars, but I can’t figure out the rhyme or reason as to which ones seem to be bugging out. Building windows also seem to be failing to reflect in reflections, and car windows seem broken in their own ways.

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DLSS 3.5? In everything that I’ve seen, it looks like temporal resolve is significantly improved compared to

Did you watch videos not sponsored by Nvidia, real gamers, or test done in non-“4k”?
RR hates motion completely because it when something moves, RR drags slime across that movement.

performance improvements are currently top of the priority stack for lumen. How lumen can function without temporal accumulation is a question for the coding oracles.

Awesome to hear the first part. But I’m not talking about dissing about Lumen slow accumulation due to a temporal design.
I’m talking about the flickering not being fixed without adding TAA or some other temporal methods like TSR or DLAA.

Currently two pathways are here-Crank up ScreenProbeGather.Temporal.MaxFramesAccumulatedto 25 to stop the flickering with SMAA, FXAA, no AA etc. But then you get light smearing when the camera pans
This is especially bad in third person games, characters get their face smeared when you pan the camera, or run etc.

Or you can lower the Cvar to 10 to stop light smearing and then rely on TAA,DLAA etc to hide lumens flickering.
I don’t care what temporal AA or pixel upscaler like DLSS, it ruins motion/gameplay.
Unless you are playing at 4k, which is not a realistic resolution since LOT of players with even $600+ systems can’t achieve 4k or even at 4k60fps.

Sharpeners are ugly and don’t fix motion smearing.
This is the oxymoron of modern game graphics.
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I don’t think ‘common sense’ and ‘game algorithm’ ever go together—
but the lumen team is doing the best they can, and I think it’s particularly kind of Daniel Wright to visit the forums and let us know what the progress looks like.—

Maybe I didn’t state that right but this post does
There is no point in making a game look amazing if upscales from 720p and looks like crap in motion. There also seems to be a lack scene specific optimization.

My message to the Lumen team: Thank you for Lumen. I could NEVER design something so innovative and complex. Know I mean no insulting tone or distaste for the team.

My distaste is for the temporal AA obsession and blurry games. Lumen is not apart of that problem except that it pretty much forces developers to use TAA to fix Lumen current issues…rather than the issues in Lumen be fixed and not slapping on TAA/DLAA etc.

and Epic has a responsibility to both userbases. I understand that you’re upset with the limitations of the technology you’re facing

Keep it very separate then. Make a Virtual production mode/preset. Because the majority of game studios’ are ran by morons and lairs. I’m not worried about the performance of my game at this point.
You should know I’m concerned with every other game not produced by me at this point.
I’m not using Nanite now that we clear test vs blindly listening the the false Nanite-hyped documentation.

The problems I present are common sense. I don’t mean “common sense” as an insult. It’s simply my way of expressing: View the entire situation as a whole, including the major challenges and issues. Including the current issues of the so called “fixes.”

A game is meant to dynamically move. Cinematics can render in slow motion and TAA/DLAA etc isn’t going to hurt it.

Speaking of the Nanite test. The Lumen team needs to not revolve fixes, quality, and performance improvements around Nanite meshes only.
Do not force people to work with a unperformant renderer.
Optimized LODs are still the top dogs in performance and a better performing background will only make Lumen’s cost less concerning for 16ms budget games.

I can’t see anything bad in the comparison above. I’m not even sure what am I suppose to see. The image from the right shows bad aliasing and exaggerated sharpness, while the image from the left is much nicer with decent anti-aliasing and no smearing or blurring.

Maybe people don’t see what you see and that’s why there’s a lack of interest.

I can’t see anything bad in the comparison above. I’m not even sure what am I suppose to see.

What is wrong with your eyes? Tekken 8 TAA motion test - Imgsli
How do you not see how much the TAA smears and blurs the character, the fence, the ground, the effects, the words, the entire background? You have FXAA or SMAA to fix the Aliasing, I shouldn’t have to say that.

A screenshot can’t even show how bad it look in motion.
Here is entire test done on motion->Tekken 8 medium motion test(Jin B+4) - Imgsli

TAA is worst thing ever happened to games. For dozens of more comparisons go here.

the image from the left is much nicer with decent anti-aliasing and no smearing or blurring.

Are you kidding me? You’re joking right? The left in real gameplay is unplayable. It’s garbage. And I mean 100% garbage. That’s not even the default TAA in UE5 which blends more past frames/vaseline.

Maybe people don’t see what you see and that’s why there’s a lack of interest.

Yes… that is major issue, showing how bad TAA can be. TAA hates motion and that subreddit shows it better than I could.

In case the Lumen team can’t see it, many other people can and hate it. They hate it so much people will drop the game entirely. I’m not saying all obviously, but a lot of people hate TAA and some people hate it without even knowing what it is.

I’m advocating here for a lot of people. Do not develop Lumen with TAA in mind.

Lumen’s flicking problem is only going to perpetuate forced TAA and TAA dependence.


For instance, Death Stranding and all of its effects looks fantastic with or without temporal AA methods.
While more and more UE games are forcing TAA on to fix several effects, like temporal hair, AO and water effect(TAA dependance, turn it off: The game look even worse with vibrating or flickering pixels).

I’m not saying you are not right, but maybe there’s something lost in translation. Maybe I’m not looking at the right spots. But one of the images has a bad case of aliasing, and the other looks all right.

Images posted with 200% zoom and also a gif animation with the comparison.

aliasing

no_aliasing

comparison

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@TheKJ , why speaking about TAA now, when it’s been the default antialiasing method (and not only in UE!) for many years? Even in UE4… for me, it’s my preferred AA, combined with a slightly sharpness post process. Never seen any artifacts, nor blur (you can disable the motion blur effect, if you want, and the image is quite clear for me). I think someone must be very special to notice any artifact in a normal usage… and I’m absolutely hard when searching for visual incoherencies.
But today you have even “better” alternatives like TSR, DLAA, AMD one… but obviously you won’t ever have all the things at the same time. There is always a tradeoff.

Anyway guys: TAA is not related to Lumen, and this is the Lumen thread. It’s already quite difficult to be read by the team here, so let’s keep this as clean as we can, if you agree, with direct feedback about just Lumen, please.

Regards!

I think we as a community haven’t done the best job keeping the thread clean and focused on lumen specifically, as opposed to various light transport conversations/technology comparisons. I’m sorry for my role in that as it is. Don’t want to make your job any harder than it already is.

I tested it myself at 1080p, and it seemed quite usable all things considered. Not perfect, but the game was legible and I had no issues with the scene.

Now that I would like to learn more about, because as far as I understand it, nanite almost always performs better with diffuse, opaque geo. Performance is non-trivial with WPO and anything similar, but that’s not a new issue. Besides, lumen effectively depends on geo for the surface cache to run as well as it is, as it’s constantly generating and regenerating mesh cards via nanite.