For me, it seems like ‘full’ Lumen gives a worse reult than Ray Tracing, but also than Lumen with some Ray Tracing features. And, even more: it (full Lumen) gives less performance.
(Same Post Process settings, forcing all possible settings to Lumen).
Please, see attached screenshots. Can you confirm the same?
PD: Edited with an updated, more evident and closer ‘context’: two spot lights on window, instead of one rect light, as above. Both with 10cm source radius, and also GPU profiling tab:
Based on your screenshots, Lumen looks far better… it has more detailed indirect shadowing and higher quality GI in general. The performance difference is hard to understand but could be explained by not using Nanite meshes, you’d have to actually profile it to see where the performance is going.
I think you think it’s better only because it’s a rect light on the window and Lumen can’t diffuse shadows as RT does. Additionally; is Lumen thought to only work well with Nanite? Then, why forgetting RT as a ‘deprecated’ feature?
If someone knows if I can share the project uploaded into my own cloud, would be appreciated. It only contains the Epic’s ArchViz Interior free project.
Anyway, let’s try in a more evident and closer ‘scenario’: two spot lights on window, instead. Both with 10cm source radius, and profiling:
Lumen:
Yeah… basically all of your frame time is being consumed by virtual shadow maps… You’d have to actually expand that to find out where the issue is but my wild guess is that its probably non-Nanite meshes.
If you want to actually figure it out then post a screenshot with the Shadow Depths rollout expanded in the profiler.
Virtual shadowmaps aren’t a Lumen feature, and they’re still experimental. They rely very heavily on having nanite meshes to be performant. You can still use raytraced shadows for your lights, and you probably should if you can since as you’ve discovered: Only raytraced shadows properly diffuse area light shadows.
Certainly, most of time was consumed by Non-nanite.
I have now enabled nanite for all SMs. Better performance (still worse than mixed with RT), but shadows are still so poor. Even if I disable Virtual shadowmaps:
So, could I conclude this?: If I (and all of us, because if it fails in a certain scenario, it can fail in anyone) want to use RT, I can’t, because RT reflections are broken (What's this trail around objects? - #2 by Miguel1900), but can’t use Lumen too, because of poor lighting on Nanite and Non-nanite meshes. I could use a mix, using RT shadows with Lumen poor reflections, but forced to not use Nanite… so there is not a complete solution, it seems; at least UE4 was already offering it (full Ray Tracing), right? Or am I missing something?
The reason you have shadow artifacts is because Raytracing uses the fallback geometry which by default is much lower resolution than the Nanite geometry.
You can fix this by adjusting the fallback geometry percentage in the static mesh editor. It defaults to 2000 triangles as I recall, and there should also be a shadow bias console command. I don’t recall what it is right now, but there have been plenty of posts on this subject and how to fix it. Details about the fallback settings can be found in the Nanite docs.
Or… you could just not use Nanite meshes. Nanite meshes are only really required if you are using Virtual Shadowmaps. Nanite will make Lumen faster, but it’s not quite as important as it is for Virtual Shadowmaps.
I wouldn’t really agree with this… Raytraced GI never produced usable results in scenes with low indirect light, it was always too noisy or slow to use. Raytraced reflections had the same issue on rough surfaces, it required an enormous amount of samples to get a clean result.
Raytraced reflections also had another serious drawback which is that they didn’t render GI in the reflections, so if you had a scene lit entirely by indirect light, the reflections would just be black. Lumen reflections by contrast, do render GI in reflections.
Lumen certainly has some issues that need to be addressed, particularly with reflections in general. Multiple bounce specular is one of the big features that raytraced reflections had that Lumen doesn’t support. But in general I strongly feel Lumen is a big improvement over the deprecated raytracing features. Just my opinion.
