Lumen uses temporal accumulation from
r.Lumen.ScreenProbeGather.Temporal.MaxFramesAccumulated which at least doesn’t blur the whole screen like TAA(and TSR cost too much or fuzzes-ups motion).
But yeah, I’ve spoken about how raising MaxFramesAccumulated above 10(default, still a lot of noise) causes the light to smear, so at the moment, it forces you to use hybrid temporal smoothing and that really sucks becuase I’ve seen some pretty dependable GI that doesn’t do this.
At this point I really want Lumen to incorporate a bakeable aspects, the volumetric lightmaps are so broken with so much leaking and memory usage. And Lumen also seems to be wasting a lot of performance on trying to figure out and re-iterate on the scene that are static even if everything is lowered to the slowest possible update. Like the noise and sporadicness could be fixed with bakeable probes.
Lumens supersamped probes is a really smart way to go about faking multiple diffuse path traced rays, but what would be more appropriate for most static games with moving lighting would be something a combination of The Divisions GI which runs way better than Lumen. Allowing us to bake supersampled probes could include super sampled world normal buffers to prevent leaking as well as depth functions to probes closest to geometry like the ones used in EA’s solution..
I guessing for a solution like this, we would need two kinds of bakeable volumes. One for indoors and one for outdoors. Indoor volumes would need the mark probes with a hierarchy in this order light source is visible, direct light is only visible, and neither visible. Then for basic dynamicism, those would only have to trace if an object is occluding the probes “view” of the light source or direct light and di probes under a lower hierarchy based on what percent of higher hierarchy probes are being occluded from whatever their tag was.
This wouldn’t be too bad to work with if each volume could have an array of profiles we could blend between and access via blueprints. Atm Lumen seems to cater to dynamic worlds, with dynamic lights, where at most games using unreal are static worlds with dynamic lights.