UE 5 Early Access issue/glitch with my foliage

Hi all !
I’m new to Unreal Engine and this forum. For a project I need to build a landscape with quite some foliage, trees, grass and so on.
The issue is that when I started to paint my foliage some… “glitches” just appeared, rapidly flashing (See video linked). I don’t really know where to look so that’s why I’m asking here.

Here is the video of the issue : Issue Unreal Engine 5 early access - YouTube

Can someone please help me ?

Hey! Are you using virtual shadow maps? The flickering could be related to that. The strange noise is caused by Lumen GI.

Some console commands you can try:

r.Shadow.Virtual.Clipmap.LastLevel = 22

you can set that to 30 and see if the shadows are getting better.

r.Lumen.ScreenProbeGather.Temporal.DistanceThreshold = 30

try 850 here and see if its better

Hope it helps.

4 Likes

Thanks for your reply !

I’m sorry I was away a long time and did not see your answer sooner :confused:
I’ll check if I’m using virtual shadow maps and try your solution when I get the time and will keep you posted !

Thanks again !

In case anyone else is wondering, Braitenbug’s comment is indeed the fix for flickering grass and foliage shadows in UE5 with Lumen.

(r.Lumen.ScreenProbeGather.Temporal.DistanceThreshold is the one you need to adjust)

3 Likes

Hi !
Thanks for the confirmation that it works !
I tried myself and indeed it does the trick but isn’t there a permanent solution to this ? I mean everytime I close Unreal the next time I open my project I need to redo the all thing in the console command.

You can build a simple editor widget that writes console commands or you can put them in the .ini.
MyProject\Config\DefaultEngine.ini

2 Likes

Yes, I put it in the .ini to avoid having to do this each time. That will be a permanent fix.

Hey man. Do you know what else could cause this issue? Asking because your solution is not fixing it. Thank you in advance

Hey. They changed a lot from the ea to the preview. There are ways to improve noise on foliage but that will have a huge performance impact. Basically you can improve it a lot by cranking up the final gather quality and setting the Global Illumination quality to cinematic. If I find a better solution to deal with the noise on grass I’ll post it here.

Update:

Try setting:

r.Lumen.ScreenProbeGather.TemporalFilterProbes = 1

That made difference for me.

What I found isn’t really a solution, but more of a work-around. I realized my foliage was flickering when the directional light was the only light hitting it, but when I added a point light or rectangular light so that it was hitting it too then the flickering was reduced greatly. The main thing is if your scene is supposed to only be lit up by the directional light then adjust the intensity and placement of the point or rectangular light so it blends in with the scene and isn’t noticeable. I’ve found the easiest way to do that is to position the directional light so it’s pointed directly at the flickering foliage. That way that area is so bright that even a point or rectangular light with default intensity will still blend in really well.

EDIT: I found actual solutions and reasons to certain foliage problems in William Faucher’s vid here Troubleshooting FOLIAGE issues in Unreal Engine - YouTube

Check this vid out and see if any of these solutions work for you.

Hi Nelly,

Thank you for the help! We cannot use youtube. Can you pls explain how they did it? Thanks alot!

In the William Faucher’s video he talks about 4 different problems with foliage. But non of those was about the flickering I was experiencing.

In my case flickering, those noisy black stains moving in foliage, only was solved when setting the scalability to cinematic.

William fixes a similar problem that appears when using wind on your foliage. It’s a complex work araound what he does, basically create a new foliage using the foliage he wants to use, and setting in that new foliage the Evaluate World possition offset ON.

Other problems solved are about shadows or foliage that disappear when zooming out.