My first try with Lumen

I’ve tried switching to Lumen GI for my archviz project, unfortunately I’m still not happy about the realism I can reach, I’m sure it’s still probably early for me to say that since I’ve recently started to learn it but, correct me if I’m wrong, I still believe that lightmaps are far superior when it comes to reach Archviz photorealism.

Lumen It’s great for dynamic lighting changes and if you want to save time when building light using lightmaps.

So far I’ve noticed that the lumen lighting is far behind compared to static lights bouncing photons. I get no diffuse effect at all, for example a red curtain diffuses some red in the room while with Lumen this effect disappears.

The ambient occlusion it’s still not that great, but I’m not sure if I’m doing something wrong.

No traslucency (but I know it’s in development), so all the glass reflections are kinda bad.

Any suggestion guys on how I can improve? Or should I stick to baked lighting?

I uploaded a pic to show my results.

Kind regards.

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I’m still learning UE5 and Lumen and Nanite myself. I’ve found you can achieve NEARLY as good as baked (lightmass) results with Lumen. If you’re going for a clean environment in your ArchViz, it’s very important to adhere to the Lumen/Nanite requirements for meshes and their materials. It also differs from software to hardware ray tracing with Lumen. The documentation is definitely your friend. I’ve found what works best for me and my environments is hardware ray tracing with ray traced shadows and no Nanite.

I’ve found one of the best ways to see if Lumen is behaving like intended is to use the Path Tracer as reference. Let the Path Tracer render for a bit to see what your scene SHOULD look like, and you can toggle back and forth with Lumen (Lit) mode and see how close Lumen is to Path Tracing.

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Thanks for your answer! Yes I have to be honest, if you use only few light sources or one simple skylight the Lumen quality is close to baked ligthing, but in a archviz enviroment with many different lights I can’t get the realism I’d like.

Do you have any advice on how to improve the Ambient occlusion effect on the heatsink in my pic? (left is baked, right is Lumen)

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Maybe try increasing the final gather quality (setting in the post process volume) significantly, to something like 6.

For something like this you might be better off using material AO

Tbanks a lot for your answer, so far I got big improvements but I still struggle with indirect light bouncing. I have a room in my scene where the lamps are facing the ceiling and 99% of the light in the room is indirect. With light baking I had the scene lit perfectly instead with lumen the room is pitch black unless I look directly at the light. Is there a way to fix this or it’s a lumen limitation?

Go into the details panel of the SM and check ‘Is emissive light source’, and then go into Post-process settings and crank the ‘Lumen scene detail’ up. Lumen culls small objects to keep the surface cache performant, which is great for dynamic world performance but means archviz requires some setting tweaking. Increasing the lumen scene detail will tell the surface cache to include smaller objects in GI, as otherwise it only has SSGI to fall back on, hence your view-dependant lighting. The ‘is emissive light source’ similarly tells lumen not to cull small emissives contributing to scene lighting.

By and large, what I’ve realized about lumen is that it is a complex, hairy beast of a system- many different techniques and optimizations are at play, and anything from open-world on mid-range PCs to photorealistic Archviz work are possible with it, as long as you know how to tweak it. That being said, they hide 95% of the advanced features and settings under CVars, even things entirely uncovered by documentation, so you really do need to go through the CVars yourself to figure out how it works. For instance, Lumen has a ‘reference mode’ that achieves super high quality at a substantial ding to real-time performance, but still far better than the path tracer.

Hey thanks for the help, I’ve set lumen scene detail up to 4, I don’t care about FPS I just like photorealism, I’ve clicked on the lamp mesh and checked the emissive light source option, but nothing has changed, actually the way I did was using one spot light facing the ceiling. If I bake light the photons bouncing on the ceiling light the room perfectly, with lumen as soon as I don’t look directly at the light I get a pitch black scene. Is there anything more that I’m missing?
Maybe since I’m not using a rtx graphic card I can’t get the lumen indirect light effect?

another thing that I noticed is that even if I remove the mesh the indirect light doesn’t change, so I guess is a Lumen interior problem and I still have to stick to static lights and lightmaps :frowning:

Now that’s a weird thing, and certainly not a problem I’ve experienced since EA. If I may ask, what build are you on? 5.0?

Oh, you’re not using an RTX card?

That would do it. Lumen was originally intended to be a more performant and inter-gen (DX 11&12) system, but they’ve since pulled DX11 support as I believe they simply found it too limiting. Your quality with software ray tracing is pretty limited, especially for small objects as they have a small volume texture (their representation in software RT). If you need high-quality interior lighting without access to hardware RT, you may just need to use baked lighting unfortunately.

I’m having a similar issue inside all by buildings…it can be bright outside and its pitch-black inside…it’s like Lumen has ZERO indirect Lighting built in or it just has no clue how to deal with enclosed spaces. On top of that I’m also getting really dark shadows on the trees around leaves, dark as in pitch black dark.

It would depend on the nature of the enclosure. Lumen is very good at resolving occlusion, so areas with no direct lighting will simply be dead black, and it could also be an exposure issue. Dark shadows on trees may be a product of an over-occlusion bug, which is a known issue lumen has that’s getting sorted in 5.1.

Yeah I figured that may be possible, but the thing is take those Western Desert Town Buildings…none of the Lumen Lighting seems to make it through those windows…no idea why, but they are solid pitch black inside…even in the middle of the day…I can legit turn my Sun Intensity up to 1000 and it will still be pitch black inside…Increasing Indirect Light Intensity on Post Process Volume or the Sun has absolutely no effect…even if I manually enter an insanely high number about 1k…

Ah, the western scene. I experimented with that myself, and it was a very strange headache for me.

Lumen and glass behave weirdly, especially depending on your translucency setup. What I’ve discovered is sometimes lumen will just treat glass as completely opaque, which may be your problem.

Thankfully, 5.1 supports lumen material translucency, and I tried that scene with the updated version to great success. Alternatively, go into the window meshes and tell it to ignore the lumen scene, that works well too.

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Thanks I’ll try that out. Appreciate the advice and support

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I FIGURE IT OUT!!! It’s the Distance Fields…they are blocking my Windows so Lumen thinks they are solid walls…

Yep, that would absolutely do it. This is where lumen’s content limitations start to get rather frustrating. I completely admire that lumen’s original goals were to support dx11 and dx12, and to be scalable, but I think it’s become clear to Epic and the Unreal developers community that the pipeline is not feasable.

SWRT needs manifold, watertight, opaque (ish) meshes bigger than a certain size, whereas HWRT will take basically anything you throw at it. The old West set doesn’t consistantly follow that paradigm, and I remember being very confused myself when lumen just seemed absolutly broken in some cases.

Is HWRT an option for you? Or alternatively, I wonder if lumen’s new stochastic semi-transparency might be useful, for the new build.

Yeah no doubt, I tried Hardware Ray Tracing though and It didn’t help either. So I’m not really sure. I’ll try again later though just to make sure. I just re-compiled the UE5.1 build to see if they ever got Nanite hooked back up. I’m going to test my project in it to see if there are any noticeable improvements.

How did they end up decoupling nanite? They just disabled the rendering paradigm entirely?