A tree in the indirect lighting, with a large building in the distance this occurs with both Lumen hardware and software, although it’s obviously more pronounced with the software version.
Occlusion and de-occlusion look absolutely terrible on these types of elements, which of course occur frequently in a game set in an urban environment.
Here’s a top-down view of the scene’s setup at this location on the map :
In this segment, still using Lumen in hardware mode, downsampling is set to 16 at native 4K with TSR, and Lumen’s screen tracing is disabled.
I removed many of the tree’s branches, but it obviously looks worse once you add back all the other branches and leaves.
I was able to reproduce the issue with a simple lighting pillar and a piece of a bus shelter as well. No AO in the scene, no screentrace, still in 4K native, Lumen hardware, etc.
Setting r.Lumen.ScreenProbeGather.DownsampleFactor to 4, for example, reduces the issue significantly, but we’re at around 20ms in 4K on a 4080. In other words, it’s slower than Nvidia’s algorithm with ReSTIR GI while being less accurate, which isn’t viable.