When trying using lumen in UE5 I’m facing visual and calculation artefacts as light failing to spread as it was supposed and also insane light calculation ghosting. I think it’s related to my driver version of gpu, because i’m using Geforce GTX 670 on 472.2 driver ver. And I’m pretty sure it’s lumen issues, because there’s no any noticeable marks, while using the medium and low scalability presets.
So, in a nutshell, while moving signifficantly in any direction amount and effect of artefacts increases, and they are FAR more noticeable at epic and cinematic scalability presets.
*I did ingame screenshot and video while using only High scalability.
(Screenshot and video was done via Geforce Experience, so there’s no “other factors” that can alter the image. )
First off, and I hate to be the one to say this, your GPU is definitely at the lower end of what lumen is capable of supporting, and I have the feeling a few different optimizations are running in the background. The high scalability setting is more nuanced than a lot of people are aware of, and it’s partly the fault of the documentation. It’s not just about ‘lower-quality lumen’, but it’s specifically geared towards outdoor lighting at 60fps. That means the quality settings assume something like a dynamic sun, a directional light that is the main light of the scene.High includes a number of fast camera settings designed to help dynamic movement look better. Epic quality is designed for stable indoor lighting at 30FPS, which means better lighting but on the assumption of less high-speed change.
Secondly, lumen in the PP volume has settings that let you control how fast temporal history flushes through the reservoir. Temporal accumulation is one of the main ways lumen gets away with such a low sample count, and your setup is almost ideal to break it. It’s not just a stationary light with dynamic occlusion and reflection, but the light itself is actually changing. You could force the lumen update speed to be faster, but that will either vastly decrease your performance or cause noise to explode, which it looks like you’re already dealing with.
In regards to that noisy artifact you pointed out, I truly have no idea. I’ve been using lumen since it came out in EA, I’ve talked to half a dozen people about it, and no one has any idea what exactly can be done to deal with it beyond blasting your quality settings as high as they’ll go. My apologies.
One last note: if this is your scene, and if it’s designed for hardware like yours with rapidly-moving lighting, then I’m not entirely sure lumen is the right fit for you. It heavily relies on caching, filtering, and persistent assets stored in VRAM (which it says you have exhausted, might be one of your problems) that it can’t really scale down that low for exactly what you want it to do. Besides, your game scene’s light is always on-screen, which would make it a good candidate for the (much faster and cheaper) SSGI.
