Hi, I’m new to unreal. Lumen is great as it give results in realtime. But I see some problems in viewport like light flickering, the reflections are blurry and not accurate and there is no translucency. when working with big environments lumen works fine but when it comes to close-up rendering its seems to fail. whereas path tracing is so accurate with lighting, GI and everything, but it comes with a cost that its not realtime.
you can see the difference in the images below, one is lumen another one is path tracing.
Is there any ways to make lumen more effective or we can expect any future update on this…
Yeah, that’s the downside of realtime 
It’s amazing Epic got lumen to work at all.
It would be nice to tune Lumen to work close up, when you approach areas like that. I don’t think it’s possible right now.
I understand that performance and reflection are areas that development is focusing on, but have no idea when we see the benefits…
2 Likes
I might be able to speak to some of that, I follow UE5_main relatively frequently and have been building experimental versions to test some new features.
To address improving lumen quality, the easy levers are of course to increase the final gather and reflections quality in the post-process volume. This generally improves the resolve of GI and reflections especially. The rock is black in your scene because geometry below a certain height and distance threshold are culled from the lumen scene for performance reasons. You can remedy this by increasing the lumen scene detail value. Furthermore, I note your scalability is set to high, which would explain some of the lower quality. High targets open worlds at 60FPS, which means near-field detail and reflection quality are degraded. Increase your settings to epic and you should notice an improvement. It also doesn’t look like non-SS GI is showing up in your lumen scene entirely, what version are you using?
There is in fact translucency, but it’s rather meagre in 5.0. Low-resolution radiance probes are used to shade translucency (in addition to screen-space reflections), and while that avoids light leaking, it means the translucent reflections are noticably dull and low-res. In 5.1, which is in production, Lumen supports high-quality translucent reflections, which are indistinguishable from the regular reflection modes. I’ve tried them out myself and they are effective and performant.
As for improvements, there are quite a few coming down the pipe for 5.1. Solutions for over-occlusion on foliage and other alpha-tested geometry, support for subsurface scattering and two-sided foliage shading affecting GI, improved reflections definition, scalability and performance, light-leaking solutions, and more, in addition to massive performance improvements in general.
I’ve tried out most or all of these features, and I’ve found they all work great. When 5.1 will actually arrive is something I don’t know, so it means these features remain walled-off to the people who know how to build UE5 and are comfortable taking risks on an unstable engine.
2 Likes
Hi, Thank you for such a brief answer. After increasing the final gather, reflections quality and lumen scene detail value, It improved a lot. I’m using UE5 5.0.2 version.
and I noticed after enabling “Use hardware ray tracing when available”, the lighting and reflection became so much better.
1 Like
Ah, you were using software ray-tracing? That would definitely impact quality, SDF tracing is worse quality than hardware triangle ray-tracing in essentially cases. I’m happy you’re having more success with lumen now.
1 Like