Why lumen looks better than baked light?

[u/Thin_Tradition8467]

I open this post because i couldn't find someone talking about it. I find lumen's cloudy day look more pleasing and realistic. It just looks next gen. Why we don't have much more better lightning in a precomputed scenario. Why baked lighting looks old.

[u/_Wolfos]

It's higher resolution. Baked lighting either uses probes, which are sparse, or lightmaps which are mostly phased out by now because they require ungodly amounts of data.

Lumen not only solves the specular response too (as others pointed out), but at one ray per four pixels it's vastly higher resolution than any lightmap could be.

But yeah, in my GI research I was amazed by Lumen in general. It looked extremely close to my path traced reference. Very realistic.

I think the more valuable aspect of it is not the graphics though. Baked lighting requires careful calibration. Different games require wholly different systems, it breaks at scale, gets incredibly awkward with dynamic time of day, etc. Limitations for days, really.
Lumen on the other hand *just works*. You turn it on. And it'll hold up in almost any project from archviz to a procedurally generated open world.

That's why dynamic lighting is becoming the default. It takes away expensive technical work and nasty error-prone workflows and replaces it with a checkbox. It doesn't need to be the most performant or best looking.

[u/Thin_Tradition8467 → u/_Wolfos]

I think i am in a wrong sub. Do you really say a premade calculation can not beat a real time one.

[u/_Wolfos → u/Thin_Tradition8467]

Comparing two graphics technologies is rarely black and white. I'm saying baked lighting has practical issues that, among other things, prevent it from having resolutions that are close to per-pixel like Lumen.

It's a series of tradeoffs. Baked does have its own advantages, it's just not resolution because that would be an enormous amount of data in the realms of terabytes for a full game.

[u/PaperMartin → u/Thin_Tradition8467]

if we had infinite disk space, disk speed and vram, which we don't, it might, but only for indirect, diffuse light coming from static light sources & bouncing on static objects. Specular light & reflections are different based on camera position and angle so will never be represented better by any precomputed solution

[u/_Wolfos → u/Thin_Tradition8467]

Sorry I assumed you were a graphics programmer and used a lot of jargon 😂

[u/Thin_Tradition8467 → u/_Wolfos]

I am not a graphics programmer but i have HLSL background. Many stuff you said was wrong.

[u/maxmax4 → u/Thin_Tradition8467]

You could technically get better diffuse GI from baking extremely high quality light maps. It would just be an outrageously bad decision to make for the vast majority of games. Does that better answer your question?

[u/maxmax4 → u/Thin_Tradition8467]

Lumen does a lot of incremental caching, that’s what the radiance cache is. You can think about it like a very large in-memory atlas of low resolution lightmaps that gets sparsely updated over time.

[u/Thin_Tradition8467 → u/maxmax4]

I know what it does. I saw your other comment too. I seriously do not understand why people keep assumings increasing quality will bring realism to your scene. It just adds details. Clearly saying, it does not change the composition. It does not change how bright the room or how surfaces reflect colors.

Maybe it's because of reddit people. I feel like people telling me if i play my game on 4K instead of 1080p, it will look more realistic somehow.

[u/shlaifu]

I'm assuming because lumen reflections are just there by default, and baking requires you to bake them. baked reflections are as good as baked reflections can be... which is not very.

[u/S48GS]

you could show screenshots comparison...

but probably refractions + GI in screen resolution

to match performance-cheap raytracing your lightmaps should be insane resolution for quality of small details and less noticeable interpolation

[u/Thin_Tradition8467 → u/S48GS]

https://youtu.be/YluSG7A_Qjs?si=N-FFHOECxEhY37sx

I don't think it is about resolution.

[u/S48GS → u/Thin_Tradition8467]

on video clearly visible - it is resolution of lightmaps as I said

0:32 time with white wall and shadows on it - you clearly see how lightmap soft shadows blured - because resolution of lightmap on wall probably 2k (2048x2048)

to compete with real time raytracing you need atleast 4k lightmaps for flat like wall surfaces

on the bed - probably even less like 1k resolution -because every soft shadow is blured

and second reason - probably this is "cheap" lightmaps - rendered on "lightmap size" texture - when you can create high quality lightmaps in Blender then downscale - for better quality (rendering lightmaps in blender will take ages)

[u/Thin_Tradition8467 → u/S48GS]

I don't think even 16k textures would introduce that cloudy day effect that i am looking for.

[u/S48GS → u/Thin_Tradition8467]

you can run realtime pathtracing on almost any Nviida RTX gpu at 60+fps - not in UE5 ofc

https://www.reddit.com/r/GraphicsProgramming/comments/1jrehm9/rtxpt_demo_is_very_impressive_especially_ray/

[u/Tentabrobpy → u/Thin_Tradition8467]

Overall the Lumen example here has a lot less contrast between shadowed and lit areas versus the baked example, which is what you'd expect on a cloudy day when the lighting is very diffuse. Note in 0:28 - 0:40 the shadows behind the plants and the board sitting against the wall, the folds on the bed, and the softer shadows in the foliage which make the plants look less plasticky (though they end up looking a bit blobby/impressionistic to my eye). Lumen also gives the scene a much greener tint, which might be more in line with what we expect when diffuse bluish light interacts with a warm off-white surface. You should be able to reproduce most of this with baked lighting just through artistic adjustments or upping the number of bounces.

In addition to that, Lumen seems to have superior specular occlusion. In 0:51 - 0:52 note the pipe and floor next to the window as well as the right end of the shelf, where reflections appear to be blocked versus in the baked example. I'm not familiar with Unreal's light baking system so this may or may not be harder to reproduce.