As of about four hours ago. It’s amazing how much improved lumen is to RTGI on scalability and quality.
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Hello, we found the issue with reflections in 5.3.1 - We use Lumen Reflections with RayTracing Reflections Enabled when available.
To explain better, I created this simple scene using Engine Water Ocean, Simple meshes and materials from the Engine folder. No post-process involved.
The example scene (as well as our original project) is created in 5.2.1. and opened in 5.3.1. later on.
5.2.1 has no glitches:
5.3.1 shows a glitch in water reflection which is annoying when you have many objects around the water area.
More examples on drive https://drive.google.com/drive/folders/1oMFA3lAuvLykfpq4i7K0s18UFKIwYVy0?usp=sharing
Can you advise please?
Many thanks!!!
Came in two days ago, curious what it means by translucent materials in lumen not casting shadows, as I wasn’t aware lumen supported any translucency at all.
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I think translucent materials were always projecting shadows (just opaque) when ray traced. Maybe they just disabled them by default to be more in pair with Lumen, which does not cast them.
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NvRTX Caustics has this function implemented: https://github.com/NvRTX/UnrealEngine/tree/NvRTX_Caustics-5.2
Are you seeing any obvious screen-space artifacts? I can’t really tell in that photo if it’s the lumen scene or not, but if refraction now supports lumen that is a game-changer. That’s actual refraction available in real-time.
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RT translucency and refraction was definitely on (notice the inverted refraction in the full bottle compared to the empty one). No artifacts besides the limited trace distance (notice the distant terrain is missing in the full bottle). There is now a cvar for showing GI and emissives under ray traced translucency. Separate options for reflection vs translucent.
I think it was on by default for translucent, but off for reflections. But when I enabled it for translucent reflections, they also began to show indirect lighting.
It definitely seems lower resolution than elsewhere, because I did get some light leaking. Not sure if it’s lumen being sampled though, or something else (like a dedicated low res RTGI).
Regardless of how it is done, RT translucency with refraction can indeed now be integrated into scenes using Lumen with much more visual consistency.
I’d still use rastered translucent for anything that doesn’t require refraction, since there is a visible decrease in GI quality when viewed through RT translucency. But for use cases like highly refractive objects it is not noticeable, and artifact free - unlike screen space refraction.
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Very cool! Is this as of 5.3, or main?
It’s sampling Lumen Translucency Volume, same one which is used for GI on translucencies. And indeed it’s lower quality than what we use for opaque stuff. Idea is to switch at some point to single layer refraction, similar as we do with single layer reflection.
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Not available on 5.3 I take it? I just tried to replicate @BananableOffense 's work and it appears to be the same light-leaking RT translucency.
This was in 5.3.
I suspected that was the case, but didn’t notice any change when messing with the translucency volume resolution so I wasn’t sure. Very exciting though, even as is. The loss in quality is a non issue for most use cases I’d want refraction for anyway.
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I tried this link and it doesn’t work. I also tried it a few times in the past as well. And it never worked. I get “This is not the web page you are looking for”
Works fine for me. You’ll need to be logged in to GitHub.
I see. Thanks. But it’s strange from their side, because I actually get more info:
Page not found.
404 This is not the web page you are looking for
Exactly like an error. While they should have said something like : You cannot view this page without being logged in.
EDIT: Nah, spoke too soon. Even logged in I get the same error. Strange.
Might you be willing to walk me through how you got it to work? Materials, CVars, etc?
The cvars are:
r.RayTracing.Translucency.EmissiveAndIndirectLighting
r.RayTracing.Reflections.EmissiveAndIndirectLighting
It appears refraction method may need to be set to IoR (even if just set to 1.0), but other than that there doesn’t need to be anything special in the material.
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Unfortunately still not interacting with lumen for me:
Translucency to raster.
Translucency to RT.
Materials very close to opaque to show effect. Indirect lighting still not visible in material, IOR in use, CVars enabled.
Also, didn’t catch this until now:
It looks like Epic is implementing its’ own ReSTIR-style many light shadow system, Github update as of about a week ago. I wonder what this will mean for VSMs, but it’ll be interesting to see how it develops. Epic had something along the lines of this in 5.1 as experimental lumen direct lighting, but I suppose this is more generalizable.
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From my testing so far, only the transmitted rays get proper GI. The reflected rays are receiving some GI but it’s definitely not the same as the translucency - not sure why. If you disable the the GI, areas like the underside of the roof will turn totally black since they receive no direct lighting. This GI appears to be the same as the depreciated RTGI.
But if you make the object completely translucent, you will see the lumen GI volume properly. This is very noticable if you toggle the effect off.
I’m still experimenting with it to see if there’s something I’m missing. But so far it just seems like transmitted rays get lumen GI but reflections on RT translucency don’t in 5.3.
In practice, I didn’t find this noticeable, unless the glass was mostly or completely opaque. I did notice it sort of lets you hack using RT reflections in a scene that is otherwise using Lumen reflections by making mirrors out of translucent materials - which is kind of interesting.
To get around the lack of lumen on the reflected rays, I tried hacking the refracted rays to act as reflections. Doing this allowed for opaque mirror reflections that were not splotchy since the translucency volume is too low res to have the noise typical from indirectly lit Lumen scenes. I thought maybe the low detail volume may be a worthwhile trade in some cases. Unfortunately there was a significant flickering artifact from my janky way of doing it that made it functionally unusable in motion, but I can show an image of it later just to show what it would look like.