Hi, Everyone. I noticed that if you settting r.ScreenPercentage to a very large value(in my case 200), and you enabled Lumen reflections and hardware raytracing, there will be visible split lines across the rendered frame. More informations:
The display resolutions is 4k(3840x2160)
I also use DLSS in my project
Engine version 5.4.4
If disable lumen reflection with r.Lumen.Reflections.Allow=0, the rendered frame became normal even if r.ScreenPercentage=200
Different screen percentage settings will cause different split pattern. For r.ScreenPercentage=200, the split line is in the middle of the width and height of the rendered frame
So how can I resolve this problem. Or is there some restrictions about the Lumen Reflections(Like some GPU buffer size or render target size).
Many thanks!!!
Checking with my peers, there’s no reason for r.ScreenPercentage 200 being invalid, nor did I find any docs stating conflicts with it. Your 4K setup should be able to render the output, at great cost, but it’s still valid.
As for the strange lines you are seeing, they sound like a bi-product from a reflection conflict. The fact that they appear right at the middle of surfaces when set to 200, sounds more akin to tiling. Let’s run a few tests to pinpoint the issue’s origin:
Fully disable DLSS, then test r.ScreenPercentage 200, as both settings could be clashing with each other
With DLSS still off, check different percentages (100, 125, 150, and so forth), and note if split appears at any particular value
Check by using cmdlet r.Lumen.Reflections.ScreenTraces 0to see if the splits are affected
Test setting r.Lumen.Reflections.DownsampleFactor to 2, which will trace reflections at a lower resolution
the splits are almost certainly the screen space trace part of lumen reflections breaking at tile borders, and 200% screen percentage is an extreme case for that buffer, the seams show up between tiles when the trace data runs out.
A/B it: r.ScreenPercentage 100 with DLSS off. if the splits vanish it is the supersampling chain, not lumen itself. then r.Lumen.HardwareRayTracing 1 if your card supports it, hardware ray traced lumen reflections bypass the screen trace path, so seams disappearing there confirms the diagnosis.
practical note: 200% plus DLSS is fighting itself, dlss already upscales from lower res. a cleaner and much cheaper frame is 100% with dlss quality or balanced, or TSR at 100%. if you genuinely need the supersampled look for a capture, do it through Movie Render Queue with its own high quality lumen settings instead of realtime screen percentage.
