Hi everyone, so I’ve been scouring the net for a while now trying to find a solution to this issue but so far to no avail: I’m having really noisy reflections using Lumen in UE5.
The thing is I guess I wanted to switch to SSGI but now I can see the reflection of some decals on the desk on the floor below…
Any idea how to fix any of those? I know this not an uncommon issue. Maybe I’ll have to wait for the 5.1
So, to be clear, you’re trying to figure out how to reduce noise with lumen reflections?
Unfortunately, you are correct. At present, there are no real solutions to reduce the noisiness in lumen reflections. There are ways to make the lumen scene itself less noisy, and there is a way to supress noisy lumen reflections itself.
Although it’s not top of mind, there is a CVar that controls the cutoff at which lumen will trace additional rays for reflections. If a surface is above this cutoff, instead of tracing rays, it will affectively interpolate ‘reflections’ from lumen’s diffuse lighting. I have comparisons of what one vs. the other looks like in the lumen feedback page, it might be of use.
By and large, rough lumen reflections are probably the biggest content restriction UE5 faces at the moment. They used to be ideal for old-school techniques to hide shadow inaccuracies with, but ray-tracing breaks them, and the lumen team seems disinclined to use cone tracing or other methods to resolve. While 5.1 does have some fixes and solutions for reflections, I’m not sure how much improved lumen reflections are. I’ll need to check.
thanks jb for clearing that up. I’ll definitely check your post in the Lumen feedback page. I guess modifying the number of rays can be costly but need to check if that’s worth it though.
There would indeed be improvements in 5.1 for reflections, but I need to check in detail too since I don’t think I have seen big steps in the list toward completely fixing the issue. It’s probably gonna take some time before we get decent working reflections I guess.
I’ll need to check if there’s a rough ETA on the 5.1 version too. Anyhow, thanks again for the help !
I should clarify: I actually meant eliminating the use of extra rays for rough reflections, basically faking rough reflections entirely. It loses detail but makes up for it in some cases with visual stability.
And I agree with you. Lumen’s biggest updates appear to be working with previously incompatible content, and obviously perf. If you find a rough ETA on 5.1, please let me know. I haven’t been able to pull down any new versions for a while because they always seem to have some vital feature disabled that crashes my builds.
As an addendum to everything I said, this only applies for the standard material pipeline. Strata, with its’ multiple-layered materials and very complex interaction with lighting, could be able to handle rough reflections with ease. They talk about addressing rough reflections in strata in the changelogs, but I truly don’t know enough about how it works to know if it’ll solve the problem.
Thanks for clarifying jb. I kind of managed to get a acceptable looking reflection in my scene by setting the r.Lumen.Reflections.MaxRoughnessToTrace set to 0.28. I feel it kind of needs to tweak the CVar to get the right balance. It’s not perfect either but it kind of works without having a lot of noise and not using extra rays.
Been digging a bit for and rough ETA on 5.1 but so far nothing comes up. Of course will let you know if I stumble upon something.
Just discovered about the strata mats. I’m no tech art or prog so I’m kind of new to all this tech particularities. It’s looking quite interesting, though not sure these applies to work with the video pipeline using mostly PBR mats. I’ll keep and eye out for these if by any chance it could be applied to that industry.
Thanks for sharing all the knowledge and info it’s quite interesting and helpful.
You bet @Bhasara , I’m hapyp to help. Happy you got a decent reflection, and you are right that the system needs tweaking. My understanding about lumen is that they began the effort by exploring and implementing many different rendering paths and features, and have been gradually refining/figuring out the right values and implemenetations for them. Reflections will get better, it will simply take time. I really do hope we get preview 5.1, it has so many powerful features on the rendering side of things that the community will benifit from. They even just added in indirect lighting brightness controls as an art knob for lumen, which is super important for good stylization.
I am decently familiar with aspects of tech art, and strata is still somewhat impenetrable for me for now. I think it’s meant to represent more diverse material pipelines, like two-layered materials but far more nuanced. I think it’ll see a lot of use as materials start getting complicated enough to match Nanite’s incredible geometric detail. I’m happy to share the knowledge, it’s wonderful to explore what the tech can do and talk to people about it. Always a good time.
Hahah yup it’s always a good time to talk about tech with other people even if I’m no expert.
I see the idea of strata when you describe it like that, it just feels natural for tech to develop improved material pipelines like this one. And yup it just feels logical to create new tech to fit nanite, what I’m wondering though is how nanite that is a UE tech only will grow in the industry? Will it become a standard? Will other public or custom engines will develop similar techs? So many interesting questions regarding tech dev 
Being mainly an artist I need to focus on art stuff (like composition, lighting, color etc…) while there are so many interesting topics to explore like this one all over the net and so many hours in a day haha I wish I had more time to dig into all that crispy tech stuff being still a bit of a techie beyond art.
I understand what you mean, only so many hours in a day. Tech art is a wonderful field in that regard because it lets you enjoy both sides of the equation, although your speciality does determine a fair bit of what you encounter.
Whether or not nanite scales to the industry at large is a phenomenal question. As it stands, it essentially eliminates the need to bake lowpolys. The tech at its’ core is certainly reproducable, but I believe it would take quite some time to get it working in another engine. Considering how deeply integrated Nanite, lumen and (soon) strata are, building an engine ecosystem that would mimic all those behaviors would certainly be a costly endevor. For the next-gen, I think Epic’s cornered the market.
Hahahha, ■■■■■■■ you’re so right. I think that indeed Epic got the market cornered It’s kind of scary when you think about it, I mean for the market’s freedom. It means that most next gen productions, be it AR, gaming, VFX etc… Would depend 100% on Lord Epic’s tech.
But hey, that’s how it is. And I don’t think I’ve heard as of now of any other company developing tech similar to this one. Even it UE5 is, as we mentionned earlier, not perfect and needs tweaking, it already a beast in the industry. I see big game dev studios and movies production one that are using it. It also feels like the era of pre-rendered 3D, like using VRay and such is coming to an end. The gap in visual quality gets closer and closer after the years. The market is definitely changing, for good or bad, only time will tell 
And I’m quite sure that at some point AI and machine learning will merge with that. To be honest I’m quite excited to see where all this goes
Also just out of curiosity, do you do that as a hobby or is also for work and such?
The market is a very big one, and Epic is advancing in some ways, and other companies are focusing on other markets. Epic’s definitely positioned itself as the next-gen high-end game engine provider, but for older platforms, smaller and simpler games, and the mobile market especially, that’s a different question. Unity has managed to make a very lightweight engine, with a lot of practical uses, for example. Cryengine had a real-time dynamic GI system for years even before hardware RT. Besides, Epic’s innovations will push other companies to try harder, which is better for everybody.
The gap is most certainly closing, I agree, but I think it will remain for just a little bit longer. As ray-tracing hardware is adopted more and more into the mainstream, the basic support for these features will increase. With technology like ReSTIR, a lot of light transport can be done in real time, but you still have to wait for certain types of features like subsurface scattering, volumetric scattering, or caustics. Give it five years though
AI and the work with NERFs will almost certainly be introduced into the engine at some point. I’ll suppose a member of the Strata team may already be doing experimental work, but time will tell.
And both, effectively. I’m actually back at school to grow my knowledge base, become better with the art side of things.
This is a very interesting conversation, and I am intending to learn about Strata.
Just OOC, do either if you know if it is the case that 5.1 and Lumen have altered the performance of subsurface scattered material and GI in a significant way?
I had been doing some experiments in 5.0 with subsurface scattering and canopy foliage that came out beautifully with Lumen. Even more beautifully, actually, when I used the Nvidia RTXGI Plugin for 5.0 (but I’ll leave that aside for now.)
But when I experiment with the 5.1 main branch, I seem to lose subsurface scattering significantly. Or maybe, now that I read this, what I am seeing is subsurface scattering that is a lot more noisy,in the same way reflections are.
I might add that the 5.1 nanite supports alpha and hence my foliage experiments, but I think the issue is independent of whether or not the material is nanite.
Anyway, I am starting to suspect that I need to understand Strata to gain better perspective on this.
@jblackwell yup the market is indeed pretty big As you mentioned with the Unity example, it’s more like they are all getting more specialized for certain applications. Unity clearly has his own crowd and platforms to focus on.
And yeah the gap between real time and pre-rendered is closing but it’s of course going to take a couple of years more to close the gap completely (Will investigate this ReSTIR tech you mentioned)
And I hope your return to school and the arty stuff is going nicely It seems like you already are quite knowledgeable on the tech side of things. If you have any questions regarding art don’t hesitate to send me PM or ask me here I’ll gladly try to help.
@ooghe I honestly have no clue ! I have not tested the 5.1, I’ve been waiting for a “full” release on the epic app. But since adding alpha support for nanite, it may be that the functionality is still in dev or needs improvement. I’ll have to investigate strata too to be able to give you a better answer. What you can try is using the CVar in mentioned earlier to check if it makes any difference with your foliage “noisiness”. If that’s the case it could be related to the same issue indeed. r.Lumen.Reflections.MaxRoughnessToTrace is the one I used. Play with the values a bit maybe, put it to 0 you may see a big difference.
Of course if it doesn’t change much in the foliage it may be related to the alpha implementation itself 
jb might be more knowledgeable on that part than me though
I actually gave strata SSS a shot a few days ago, and the results were…inconclusive. I only ran initial tests on simple strata materials and a few parameters, and SSS in UE5 is one of the less intuitive pieces of tech on the engine. I don’t fully understand what my parameters control (or if they’re even hooked up to actual material behavior), but it appears strata supports most expected SSS features. It’s still a diffusion-based approach, which I’m not super happy with, as RT SSS allows for much more accurate and complex light transport behaviors.
For lumen, I couldn’t say. I built UE5_1 yesterday and I’ll do more tests.
I would genuinely love to take you up on that. As part of our courses, we have everyone from complete newbies to semi-experienced professionals, so our first battery of courses is getting everyone up to speed on basic art. 2D concept drawing is kicking me right now, I’m now fully grasping how hard it is to generate good-looking light without an algorithm painting it in for you. Are you an artist in the industry?
And absolutely, check out ReSTIR and the derivative algorithms. It’s basically technology that can facilitate real-time path-tracing for many-light scenes (IE hundreds+) at less of a cost. I’ve read through the white paper a few dozen times and I still only understand so much, plus the algorithm’s been reworked a handful of times since its’ debut. Essentially? Low-noise path-tracing for about 2SPP, with options to scale up or down.
The gap is absolutely closing, and competitors are trying to catch up to Epic. Just a few days ago, Nvidia announced their micro-meshes system, which is based on an Adobe paper on displacement maps for ray-tracing plus some lessons from nanite and mesh shaders I believe. Unlike Nanite however, it can support partial opacity and ray-tracing against the raw geo. It’s also an open-standard, with mass adoption in mind. Cheap, real-time path-tracing against things with almost unlimited geometric detail is coming soon-ish, and how the industry will adapt will be a fascinating thing to see.
So yes, I do love the tech side of things. But with a chance to learn art, I’m really happy to challenge myself in new ways.
ahhh traditional art XD I’ve been learning concept art and drawing for years before switching to 3D which suited me better. So I feel you haha But it’s still good practice to get the basics indeed. It can be quite frustrating though Keep it up and don’t despair haha
You’re drawings will probably look like 5 years old stuff at first but it’s quite normal so don’t worry about it
And no I’m not in the gaming industry. Tryin to get in for quite some time though. I’ve been improving for a while now, working with UE in environment art. Here’s a link to my stuff if you want a peek ArtStation - Daryl Kidjo
If you’re struggling with specific stuff, shoot I may help. A good book if you want to get a reference is “Drawing on the Right Side of the Brain”. Don’t know how far they’re going to push you traditional art stuff but that could help.
I quickly checked out ReSTIR and it looks like cool in development tech ! I saw they had the paper attached to the page, but too much tech stuff and my brain melts haha But It’s awesome to know such things are developing !
Nice the stuff with Nvidia ! Didn’t know about that, thanks for sharing Especially being open-standard that’s clearly a plus. As you said, nanite etc is quite good for the industry development as a whole We’ll all need RTX card in a few years haha I’ll check that tech out too !
You got that jb, challenging yourself and always evolving is always greatly rewarding and interesting We evolve in a awesome industry for that haha
I did! You did cool stuff, I like the console in particular. And funnily enough, you’re the third person to tell me to read that book. Guess I should give it a shot!
And yeah, the tech is really complicated and took me forever to understand. Your compliments are much appreciated and I am also impressed by your enthusiasm and willingness to learn/challenge yourself as well. We are in an awesome industry, yes!
Also, checkout what I posted in the lumen feedback thread if you’d like. Some new features just came down (~5 hours old) and UE5.1 might get a lot more interesting.
Thanks for the kind words on the console haha Glad you like it
Well if I’m the third person to recommend you that book go for it when you have some time, I think it may give you really helpful tips !
And I quickly checked out the feedback thread yesterday night, looking promising ! Also investigating strata a bit more looks quite awesome haha I really need to build the 5.1 to experiment with all that ! I’m just a bit short on SSD space, having already 2 versions of UE on it + projects files etc… hahah
I also discovered the work of BananableOffense ! Awesome stuff he’s doing, very insightful ! I see you’ve been taking about this & that with him for some time Looks like a cool person also haha Will dig more into his stuff to get a better grasp of what’s under the hood of the beast UE5 XD
