I’ve recently advocated for a transition from Unity to Unreal within my company, primarily because of Unreal’s superior Raytracing capabilities, which are critical for our high-end luxury watch visualization projects. However, with the ongoing development shifts towards Lumen, I find myself increasingly concerned about the future quality of our projects in upcoming Unreal versions.
While I understand the advantages of Lumen, particularly for organic environments, it does not yet meet the high standards required for the precise, clean reflections necessary in luxury product visualization. In recent DevTalks, it’s been explained that Lumen uses a Signed Distance Field to simplify environmental representation for faster calculations. This approach, while efficient, cannot replicate the exacting detail and quality provided by Raytracing.
Given that Raytracing is essential for content creators who require 100% accurate reflections, I am compelled to question the decision to phase out Raytracing entirely. Are we risking alienating a significant segment of the professional community that relies on these capabilities for their work?
I urge the Unreal developers to consider maintaining Raytracing in future versions or at least until Lumen can genuinely match its quality. Removing Raytracing now seems premature and could potentially hinder many users like myself, who depend on Unreal for high-quality product visualization. We need tools that do not just work well but excel in rendering the high-detail, reflective materials typical in jewelry and watchmaking.
I appreciate any insights or suggestions on how we might address these concerns moving forward.
We aren’t deprecating ray tracing. We’re deprecating standalone ray tracing features - Ray Traced Reflections, Ray Traced GI etc.
Lumen can use both distance field ray tracing and triangle (hardware) ray tracing. It also has its own path for GI and reflections, so there’s no point in maintaining two features solving the same problem.
Thank you for your clarification regarding the integration of ray tracing features into Lumen. I appreciate the effort to streamline rendering capabilities within Unreal Engine.
I understand the rationale behind merging these features; however, based on our recent tests, we have not yet been able to achieve the same level of sharp and precise reflections with Lumen as we could with standalone ray tracing. This quality is crucial for our high-end jewelry visualization projects. I’ve included a link here PLEASE ! - Don't remove Raytracing Reflection (Deprecated) in 5.4 to our tests which illustrate the current challenges we are facing with achieving the desired clarity and sharpness in reflections.
Given this, I would be grateful for any suggestions or guidance on how we can enhance our results using Lumen or if there are upcoming updates that might better support high-detail reflections necessary for luxury product visualization.
Hard to know for sure without being able to compare in that content myself. Here’s a list of differences between Lumen Reflections and RT Reflections:
By default Lumen Reflections use screen traces, which may help or not. RT reflections didn’t have those.
RT reflections used reflection captures and unshadowed skylight for things in reflections. This can be enabled in Lumen through CVars. r.Lumen.HardwareRayTracing.LightingMode 3 for unshadowed skylight and.ReflectionCaptures for reflection captures.
RT reflections exposed whether shadows in reflections should be area or hard. Lumen uses only hard, as those cause less noise. In 5.5/UE5-Main this can be changed using r.Lumen.HardwareRayTracing.HitLighting.ShadowMode
RT reflections denoiser is sharper. Some of it can be made sharper in Lumen using CVars. Try for example disabling bilateral filter using r.Lumen.Reflections.BilateralFilter 0. There should be new denoiser in 5.5 which will make everything sharper though.
I have to agree with Daniel. In my line of work, which involves motion design and visualization where visuals are scrutinized closely, the mandatory use of Lumen in version 5.4 has resulted in a noticeable decrease in quality. Both reflections and shadows appear less accurate compared to the deprecated hardware version. This is especially apparent on surfaces such as cars or materials that verge into glossy territory (roughness levels of 0-0.25).
Previously, I could adjust quality/performance using the number of rays, but with Lumen, I only have the quality slider and a few mentioned cvars to attempt to enhance the appearance. The persistent moving noise, especially when attempting to improve reflection quality, is particularly troublesome in my projects. A lot accuracy is also lost in relfective surfaces with subtle roughness or normal variation. They appear much rougher than they should. This becomes a big issue when I’m trying to replicate my clients materials, as it doesnt represent them closely enough.
It’s a real shame because there are lots of great reasons to use 5.4, namely nanite displacement improvements, the new motion design mode and the big improvements to sequencer. A real dilemma for me almost forcing me to stay on 5.2/5.3. I havent time to provide screenshots, but they are similar to Daniels, just wanted to chip in with his worries.
I think it’s pretty clear in Daniels linked post with screenshots
I need to find time to create comparison videos/screenshots but I’m mid project so can’t find the time.
Again main issues:
Lumen reflections are not as accurate nor as sharp as hardware raytraced reflections (depreceated). Even when using a mirror material (roughness 0 - 0.05) I get some sharp reflection and then moving blobs on top which seem like some sort of approximate samples of my surrounding environment.
Lumen shadows are much noisier and less accurate than their hardware raytraced (depreceated) counterpart. Where before I could just increase the number of rays on a light if the result was too noisey, doing the same with lumen doesnt seem to have any effect. This is most noticeable on large soft lights like rectangle lights.
Quite frustrating that it feels like I’ve loss quite a bit of control. While I appreciate for games etc the results are good enough, for me the quality drop is noticeable.
I can see differences, but in order to understand where they are coming from I would need to be able to run this project on my end, change settings, CVars etc. So if you can send a repro or show this based on available UE content then I could dig in and figure out what’s wrong here. If this is only screenshots, then I can only speculate what causes those differences.
With roughness [0-0.05] denoiser is completely disabled, so they should be 100% sharp.
As for the moving blobs, I guess that’s GI in reflections. RT Reflections used static lighting (lightmaps/reflection captures + unshadowed skylight) for hits in reflections. If you want the same, then you can disable LumenGI and maybe will need also to enable r.Lumen.HardwareRayTracing.HitLighting.ReflectionCaptures 1 if you use those in your content.
In any case, with relying on baked lighting/unshadowed skylight reflected scene should look 1:1 the same between Lumen Reflections and RT Reflections.
What do you exactly mean by “Lumen shadows”?
Lumen is handling only indirect lighting. If this is about ray traced shadows and VSM, then it’s outside of Lumen and I don’t think anything changed there.
If this is about shadows in reflections, then that should work the same, we just have a different default and now all lights in reflections cast hard shadows. UE5-Main/5.5 got a new CVar to change that (r.Lumen.HardwareRayTracing.HitLighting.ShadowMode) and we’re thinking about exposing it in the PPV.
This is a very small matter, but I would be grateful if you made that a PPV-editable setting (although I vaguely wonder if more drop-down nodes are needed for the lumen settings as they’ve accrued more and more options).
While not a problem in most scenes, I’ve definitely seen situations where the large discontinuity between the very soft shadows of an area light look quite strange next to the razor-sharp lumen scene shadows. A toggle would be very nice .
Same issue here as @dpotuznik , lumen doesn’t hit the quality required yet for rendering videos. I can’t share my repos because it’s 50+ Gb unless you dm me.
I’m also using RT reflections in a game (thankfully still 5.3) and I couldn’t get lumen reflections to render as sharp (reflections are vital to my gameplay).
Phasing out Raytracing in 5.4 is a rushed decision I think – until there’s an easy checkbox in the PPV to get the same quality as RTReflections with Lumen Reflections, I still need RTReflections.
Also agree with the above - I had to change the direction of a project recently because I couldn’t get the reflection quality I was used to with RT reflections but hadn’t realised it was missing from 5.4 when I started work on it. If lumen really can achieve the same quality then it would be great if these settings could be bundled into a single PPV toggle (perhaps with a warning that it’s slower).
here you can see the difference between raytracing and lumen
on the first image you can see the detail in the reflections and it’s very precise and sharp.
on the 2 em it’s much less detailed and especially if you move you get a ghosting effect that’s really not very pleasant.
I’m attaching my project, maybe I’m doing something wrong, but I’ve spent hours on it and it doesn’t come close to the quality of raytracing.
One major missing piece is number of rays per pixel. In this scene your standalone reflections were set to 8 rays per pixel, but we don’t have this control in Lumen reflections at the moment and they trace only 1 ray per pixel. We’ll investigate adding a similar control to Lumen Reflections, but at the moment the only way to improve it is increasing general screen resolution with screen percentage.
When you set screen percentage above 100% you supersample your image. So if reflections trace a single ray per pixel then with screen percentage set to 200% you will get effectively 4 rays per pixel.
Same applies to the Path Tracer, but there you have explicit controls for the number of samples per pixel and don’t really need to touch screen percentage settings.
thank you very much for all the information and tips. However, I have another problem with Lumen Reflections. It is the inability to display translucent materials in reflections. As far as I know, this is only possible in screen space and a workaround would be to work with an opaque proxy. but this does not work with niagara and gaussian splatting…Therefore 5.4 is completely unusable in currently 3 running projects. A great pity, as it brings so many great changes. Is there a solution in sight or can you tell me a solution approach for this? Unfortunately pathtracer is neither an option alternatively, I would also like to see the deprecated but reliable standalone raytracing back again until lumen can catch up.
Thank you!
Transparency should work when you set max refraction bounces in Lumen Reflections and have hit lighting enabled. Likely you need also to disable screen space traces, as they won’t pickup translucent stuff.
Thank you Krzysztof,
unfortunately the settings do not add any value. Not even at maximum. Or am I doing something wrong? With Screen Traces at least some GI and reflections are added. But they are very imprecise and “ugly”. But it’s nice that the checkbox is now available. I tend to have it off by default.
Do you have any other hints please?
I have attached a Pathtracer Screenshot with 512samples/pixel and Denoiser on to see how it was intended and we had close results with standalone raytracing.
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alternatively, I would also like to see the deprecated but reliable standalone raytracing back again until lumen can catch up.
