Lumen GI and Reflections feedback thread

[Yaeko]

Thanks, thought it might help to visualize the changes, given that its the exact same project/game.

Translucency, yes and no - I think some improvements were made, but trees (masked) are still (obviously) broken.

SSS, definitely, which is why the whole scene there has an orange tint, due to me having subsurface “sunshade-things” on the roof-windows.

As I said in earlier posts, Instanced Static Meshes also now work with Lumen, a lot less noise and many smaller improvements.

did you do anything different than with the bushes?

No, the bushes are from the same origin (creator), but they always behaved differently, probably due to them not being as large as the trees, therefore the engine treating masked as opague not having as much as an effect. (Imagine the trees as large “panels” blocking the light, while the bushes are much smaller “panels” - thats most likely where the difference comes from, and the bushes are closer to white surfaces too.)

Tbh, I think it is partially because this is a brightly lit area (there is a lot more bounce-light now, it seems, in comparison), since in other areas the bushes are dark too:

See the “usual dark bushes” here, also: GI from SSS (the triangular roof panels)

In my github build, Emitter light is flickering though, therefore missing in the screenshot currently, which is why the jump pads there look “weird”.

TL:DR is: Epic improved a LOT, its clearly visible, but there is still things to do, oh, and obviously performance went down a bit too.

[okaifas]

Are you sure? I swear I have never seen this before in previous versions of UE4. This occurs even when there is no other object in the scene.

[okaifas]

I’m installing 4.27 to see if I can reproduce it.

[Arkiras]

@okaifas

Are you sure

100% sure. One of the first questions I ever asked about Unreal was about this exact issue.

[okaifas]

Well, I can confirm it does not happen on 4.27.2

[Arkiras]

Yes, it does, and always has:

The exact appearance of the issue will vary, especially in UE5 when using virtual shadow maps as it has fewer controls and way higher resolution but the issue is inescapable.

This is not specific to Unreal either, here’s a thread about the issue in Blender: Is there a workaround for the terminator problem? - Lighting and Rendering - Blender Artists Community

[okaifas]

Why exactly does it not appear in the screen I posted, then?

[Arkiras]

Because you’re using the default map which has a stationary light with inset shadows

Switch it to moveable (or disable inset shadows) and then set the dynamic shadow distance to something small like 5000 and you’ll see it appear. This issue is in some ways resolution dependent and having less resolution will help obscure it.

[Yaeko]

Guys, Girls, this is not a Lumen issue, obviously.
This is shadow related.

[okaifas]

But apparently it is UE5 related? Because if I setup a default scene in UE5, the issue is very obvious.

Also, I set the directional light to movable in UE4 and I still cant see the artifact…

[okaifas]

Also , sorry if I sound argumentative–this is not my intention. I’m just trying to figure out how to remove these artifacts.

[Arkiras]

@okaifas

I’m just trying to figure out how to remove these artifacts.

I already gave you the answer in my first reply; Use more geometry.

Left: Default Sphere
Right: Sphere with much more geometry

Otherwise just disable virtual shadow maps. Your call.

In the future maybe we’ll have more controls over VSM but for now this is what we’ve got.

[okaifas]

See, here’s the answer I was looking for–it’s related to virtual shadow maps, then?

[Yaeko]

Done some investigations on “trees and leaves”, since the question was raised…

It seems, at least in my Github build, its partially working.

The “overshadowing” is dependent on the distance to the next surface:

Very visible here, the wrong color of the “shadow”, given the surrounding environment color, which is green - on certain distances it simply doesnt “get through” → turns black instead.

This would also explain why the bushes in my above screenshots are mostly fine, while the trees are not - because the trees are in that “deadzone” for Lumen, it seems, due to the distance between the planes the material is on.

In trees, this obviously becomes an issue quickly, given the distances between planes:

I hope this helps to visualize the translucency improvements and remaining issues.

[zbieraj]

Can you paste the link to the newest version on GitHub, please? And is there an easy way to compile it? Noob here who always use the Epic Games Launcher for using 5.0EA.

[LivelyGeek]

@zbieraj - I made a quick tutorial showing how to compile UE5 from source code here: Building Unreal Engine 5 from Source Code - UE5 Game Development #2 - YouTube

You’ll want to checkout the ue5-main branch though, not the EA2 tag in the video.

[zbieraj]

Eh, so after the update the PostProcessVolume, when in the area of it, it shows flat shading. When turning it off, it looks fine. Also, the new IOR system does not work properly now.

[Yaeko]

Is the House a single mesh?

if so, lumen wont work properly with it because of “how it works” - you simply cant use complex meshes that are hollow with lumen. The Mesh Distance Field wont have enough details.

It doesnt look (too) wrong on the outside though, given the overexposure of your image, but the inside definitely is “wrong”.

[zbieraj]

1. Nope, it is not a single mesh.
2. It worked just fine with 5EA2.0.
3. It looks really wrong outside :D. After turning off the PP, it goes back to normal.

By the way, the IOR in the recent GitHub build is totally broken…

[Yaeko]

Github builds are obviously a bit “hit and miss”, some are fine, some are not - usually something is broken, somewhere - but if you find a stable build, the benefits outweigh the annoyances by far, given how “bad” EA2 was at “doing lumen stuff”, at least in comparison to my december build.

But, that aside, your house doesnt benefit from the improvements as much as a game does, given the scale differences etc. - so maybe EA2 is the best for you, at the moment.