Lighting problems in Unreal and their fixes

[@edwardhoare7617]

I'm three hours in troubleshooting lumen crawling and even though I have yet to find a solution, you made me not feel alone. FML

[@sherwyn7436]

Dude did you find any solution? its been 1 week since i tried to fix it all the solutons and all posted by others dont work for me

[@LousyNine]

@@sherwyn7436 Just made an animation for my most recent scene. The crawling comes and goes as the camera enters and exits areas with more/less light. I've tried so many things, but nothing is fixing the issue. My lighting is all very standard, and I have absolutely no idea of all the things that can go wrong, why some weird crawling of light happens. Is this something that studios just have a fix for and don't tell anyone?

[@juandavidhoyosarquitectura]

@@LousyNine Hello, I had the same problem, apparently it is a problem related to the emissive materials, I solved it by lowering the value of the emissive material but I am still looking for a solution

[@geoffalday]

Great video! That Lumen Crawling one is definitely annoying. When recently working through that issue, instead of increasing the final gather, I tried a couple of other things to mitigate it: 1) Added a secondary light source as a fill light, that doesn't cast shadows, to slightly bring up the overall light level. My thinking here is that it gives Lumen less to calculate overall so it can handle those bounces more effectively. In my case, I'm using a lot of emissive light sources and this helped reduce the crawling enough to be happy with. I had to adjust/rebalance all the various actual light and exposure levels too of course. 2) Used exponential height fog to hide Lumen Crawling in the distance. Might not be feasible depending on what people are going for, but I figured since I didn't want players to see too far into the distance anyway, I might as well just hide the crawling. Not a perfect solution but it did help.

[@CraigPerko]

I haven't had much luck with increasing the fill lighting. I explicitly tried it, but I couldn't do it without softening the shadows to the point where it looked day-for-night.

[@geoffalday]

@@CraigPerko I wish there was an exact way to fix it that didn't require a hit to performance. The fill lighting I'm using is just barely there.

[@madeeasy7148]

Yeah there's a fix for the luman crawling, there's a guy on KZbin called William and he slides two sliders and it helps get rid of it

[@frankyjoy222]

@@madeeasy7148 link please? Lumen Crawling has been so annoying.

[@outtoplay]

Interesting issues. Props for bringing this up and starting a conversation. Will keep an eye on this for sure.

[@CraigPerko]

Well, I hardly think I'm the first one to notice. It's just that these days Google is crappy and everythings lost in a mire of Discord channels.

[@TK-11]

Good stuff. The only way I found to solve the Lumen crawling issue was by increasing "Final Gather Quality" too, however this setting can also be found in post process volumes under the "Lumen Global Illumination" section allowing bounded volumes to be placed only where the boost is needed. It's just your same workaround but with a bit more flexibility in how it's applied.

[@CraigPerko]

Oh, good find!

Geez. I've been trying to figure out that camera cut pop for ages. Thank you!

[@beo1863]

for light flickering , you can go : Project settings, Rendering, Default Settings, Anti-Aliassing Method, and choose Temporal super-resolution (TSR) , it work for me

[@clorece]

Im not completely sure how lumen does their filtering calculations or their global illumination, but I assume that disco artifact is probably caused by a svgf (or svg) filtering problem, i think the weight, threshold, or radius for the filtering is set too low. Im not sure if its exactly svgf but its most likely a filtering problem that is supposed to blend and blur ray bounces.

[@clorece]

if you can find the settings or parameters for the filtering they used for lumen, try increasing the weight (this effects the overal color of the ray sample but increasing the strength of the filter), increasing the radius (this blurs the rays in larger radius so think of the disco circles to just be extremely larger but less noticeable than tiny disco circles) or decrease the treshold if there is any (this would allow the filter to filter out a higher range of colors the rays produce)

[@CraigPerko]

I have absolutely no idea where those settings would be, but I'd settle for a tutorial if I could find one. It's so hard to search for these kinds of things because technical terms like "blotchy" give a million other completely unrelated problems.

[@TruongNguyen-xc6ek]

Pls help me how to fix this. every time i move my character or model in ue5 by lumen lighting, its create some light leak so annoying ( one to one frame then nothing happen but every time i move some frame in sequence light leak appear and disappear right few second ).

[@CraigPerko]

Unfortunately, there's a lot of things it could be, and I can't help you since I don't know which problem you're having. It sounds like you might be annoyed by light recalculation delays. You may want to make sure you're set up for realtime only lighting, which may help.

[@marvinrautenberg9061]

You can fix lumen crawling By increasing your light intenity drasticly and compensate the now bright light in your exposure Settings

[@Niro_sounds]

How do i fix light leakage? between walls, etc

[@CraigPerko]

Well, you could add walls on the "outside", otherwise you'll want to look it up from a specialist video, it's a little involved.

[@W.420]

Thanks for open this! I work with UE for Archviz and this crawling is a big Problem for me. The only way to fix it was do lot of lights in the apartment but now the shadows and performance are bad - second i must delete post process volume… anyone now if it is fix in 5.2 or 5.3?

[@CraigPerko]

It's not fixed. You can mitigate it a bit with the techniques in the vid, though.

[@juandavidhoyosarquitectura]

Hello, I had the same problem, apparently it is a problem related to the emissive materials, I solved it by lowering the value of the emissive material

[@Preirin]

This is great - thank you. However, as I am relatively new at UE (5) I am having an issue I can't seem to fix and you seem to be the go-to genius for these issues (subscribed, btw!) I don't know what I did in my landscape but I have a weird "wall of fog" that clears only around a certain radius of my camera. It's not the HeightFog and I have no idea what I did or deleted that created this; it just appeared one build and now I can't get rid of it. Do you have any suggestions? Cheers!

[@CraigPerko]

There's a few things that can create that effect, but all of them are things you add to your scene or project - none should just suddenly exist. So try creating a new scene - does it exist in that scene? If not, slowly set the new scene up with the core features of the existing scene - which feature turns it on?

[@Preirin]

@@CraigPerko Thanks for the reply. I turned everything off and on one by one and it seems that the issue is linked to the sky atmosphere, but I am not certain why. I'll dig around in that function and see what I can find out, if anything. Edit: Playing with the ground radius does change the issue. Lowering it to 1.0 makes it disappear but my sky looks horrible. anything above 2.0 makes the issue visible. It couldn't be the height of my landscape, could it? it's at 100x100x100 in location, so I can't see how...

[@CraigPerko]

@@Preirin I'm not familiar with the intricacies of a sky atmosphere, sorry! But there should be tutorials that can cover it.

[@joerwk]

I couldn't tell from the video, are you using any emissive materials here??

[@CraigPerko]

It's possible things have changed since the video, but as of the time of the video, emissive materials were extra buggy in low-light conditions.

[@joerwk]

@@CraigPerko I started using UE from 5.3 so I'm not sure how bad it was before but it definitely still exists to some degree. I'm asking you if the first problem in the video is caused by emissive materials on the torch/wall or just the regular lights added from the drop down menu?

[@CraigPerko]

@@joerwkRegular lights. But emissive materials are similar, just a bit worse.