I am trying to resolve an issue in my scene where the lighting is constantly moving and shifty even when I am motionless. For example, in this short video, i have a few fairy lights with emissive material on them, but the emissive light being cast is constantly shifting and moving… I assume its some kind of optimization or project setting but i cant figure out which? It looks almost like the samples are not fully resolving.
This only seems to effect certain light sources, such as emissive materials, but also my SkyLight which uses an HDR map as a source.
I am using Unreal 5.2 for my project setup… Note that I’m not interested in performance improvements as i’m rendering all of this content offline so im just trying to get my lighting to look correct in my viewport in order to balance it.
This is just how Lumen deals with small, bright emissive sources. If you aren’t concerned about performance, the simplest way to deal with it is probably to make the bulb materials translucent so they don’t inject lighting into the scene, then add a point light inside each to cast the light instead.
Ok, that’s both good and bad news, as then i lose the bloom effect from the emmisive source, and the fact that emissive surfaces can be any shape while a point light can only be well… ‘a point’ …
Can you not increase the amount of detail/resources that lumen uses to gain more accuracy (at the cost of performance?).
Not enough to fix this. You can have an object with an emissive material still. Not 100% sure if It was this way in 5.2, but emissive materials set to translucent don’t inject light into the scene (while still visually glowing). Thus you get the look of the glow, but not the noisy light.
Then, you replace the noisy light with the clean point light. This gives the best of both worlds.
Cool (and thanks for your help so far), ok i can try that…
But what about my issues with the HDR map on the Skylight … thats also wobbling around (infact that one changes as i move around the scene) Ill try and grab you a video to demonstrate.
I’m not sure how to deal with it for a skylight HDR. I’ve heard the command ‘r.Lumen.Reflections.ScreenSpaceReconstruction.TonemapStrength 1’ can reduce noise from emissive lights, but it has some tradeoffs. Maybe it’d work in your case.