Sorry for disturbing, but you are also involved in Path Tracing development, right? Please, if not, could you @mention who correspond? (As many other people I have read, I don’t want to use the bug submission form anymore, to be ignored for the 10th time in the last years, apologizes).
I have noticed most AMD cards seem to be not compatible with PT (crash), while most Intel cards seem incompatible because they show a black screen. (Curiously, some specific models or families, seem to be compatible, like the 7900 AMD series or the Intel “A” family).
You can see this clear behaviours in GameTechBench software, from Steam.
As a last thing, if you have direct access to him, please, could you just share my post link to ask him to read it? Maybe he could “move something”, if he considers it.
Please re-enable Lumen for DX11 in UE 5.5.4. Depending on the GPU and scene complexity, enabling Lumen in DX12 will cost at least 23 - 35 fps, but because DX11 has at least a 28 fps performance gain, this helps offset the cost of Lumen. Thank you!
small note: i don’t like how much noise the surface cache produces in raytraced reflections, targetting glass or very reflective materials. a step down to the irradiance or baked kinda volume representation would be nice in those cases. i’ll try to do it myself the next days, it’s a lot of graphics code to dig thru tho. : )
also… i would like the possibility of a cheap flashlight only gi pass in a baked level. if you know what i mean.
hello. unreal 5.5，Lumen cannot reflect fog, volume fog， And transparent materials. I couldn’t find them in the Lumen scene either. Is there any way for me to reflect the river and high fog? I used hardware ray tracing and GI used hit light. However, highly reflective objects in the scene, such as the reflection of buildings, cannot see the correct effect. Is there any CVAR or method that can solve it
Thank you for your reply. This method can only increase the reflection fog, and my volume fog and transparent river still cannot be reflected correctly. Currently, I can only use screen space reflection by pulling away. Thanks again
Volumetric fog can’t really be integrated into lumen reflections AFAIK. You can insert the transparent river into the RT scene via raytracing. Make sure r.RayTracing.ExcludeTranslucent is 0, and r.Lumen.Reflections.HardwareRayTracing.Translucent.Refraction.EnableForProject is 1, and translucency bounces for lumen is set to 1 or greater. Let me know how that looks.
By the way, (and if it’s just in the documentation and I didn’t see it then sorry for bothering people), has the Lumen documentation been updated with the new information on how transparency works? Even after a good deal of experimentation I’m still not entirely clear on how transparency works with RT, does lumen transparent refraction only work for secondary bounces (refraction visible in reflection) or will it actually be used to resolve primary view refraction?
You are right, I tried using your method and it now reflects the scene correctly. Now I have adjusted and turned off the scene fog and volume fog, but there are still some differences in the reflection effect, such as the sky color and the reflection scene gi. However, the current effect is already very good. Thank you very much for your help
I have a stupid-question for the lay-people out there, I’m not so well-versed in all the math-stuff, but what would the difference here be for a screen-space-reflection vs a lumen-reflection? What other-stuff would we be getting in lumen, what would it (supposed to) be rendering vs a screen-trace?
Would the reflection itself be contributing light, etc? Unsure what lumen might provide vs sampling the final-image in a ‘classic’ reflection.
Screen space reflections are great because they can reflect things that don’t show up in the lumen scene, and the things it reflects can be of higher quality than the lumen scene, but it doesn’t work at the screen edges and there can be disocclusion issues for example if a tree is partially blocking a view of a lake. It’s also common for ray tracing to have issues with skeletal meshes or have them be black in ray traced reflections so screen space will fill in that missing data.
Lumen reflections fix those edge artifacts, allow reflections of things off screen, and minimize disocclusion artifacts. It also helps better represent rougher reflections and semigloss where screen space can struggle and often has a roughness cutoff.
You can visualize this with the node “raytracing quality switch”. Set an object up to be green in the standard view and red in the raytraced view or something. When you view the object in a mirror, you’ll be able to tell what parts are using screen tracing vs raytracing.
Unfortunately, it’ll be very difficult to impossible to get a complete reflections/GBuffer match with lumen, the lumen scene is ultimately an approximation no matter how much you crank up the settings. A complete match is only really possible with the PT. That said, your lighting is really different between the two scenes, for reasons that aren’t actually clear to me.
To add a bit, you can also adjust what buffers SSR is drawing from when tracing rays. 5.5 gives you the option to use (I could me misremembering) a lower-res, anti-aliased series of buffers, which provide more image stability but fewer details. That’s a meaningful tradeoff if your game has a lot of dull surfaces that are more likely to have reflection noise.
Hi! Here you can see a comparison beween pathtracer and lumen in UE 5.4. Its situations like this where I notice that lumen just lacks bouncelight intensity and saturation. This is with the diffuse color boost set to 4 and Indirect Lighting Intensity from the DirectinalLight set to 6. So far I could never even get close to what the pathtracer does. Anyone has some tips for me?
