So for instance, here’s what I’m talking about with the thresholds when using HWRT:
I set the sun angle low on this to really stress the shadows. Note how the long shadow popped in as I descended. I went all around the scene looking for weird light leaks and didn’t have any issues.
It’s possible you’ve got some poorly set cvars or something that have carried over from migrating or something.
Again, reread my description: default project, I made no changes. To ensure I didn’t muck with something under the hood, I resorted to using a default project with default materials (the worldgrid) and still get the same results.
I am very-willing to admit I can make a mistake, point of order, I assume I made a mistake before giving this kind of feedback, hence my exhaustive search for configuration-settings; PEBKAC is an acronym for a reason… 
If it works for you great, but it’s not working for me, in a relatively straightforward testcase.
What are your system specs, driver versions and OS version? This could boil down to some GPU precision fallback or something.
I’m really not seeing any of these issues in my testing. Maybe test in standalone to see if you’re not just having some editor glitch?(sometimes bugs like this can happen if the editor is sitting there hogging 20gb memory, usually you just have to restart the editor or play in standalone)
Win 10, RTX 4060, don’t recall the driver I was on before I tested but to be sure I did upgrade to the latest 572.16. Tried both game-ready and studio drivers.
Always test in standalone, even package it to ensure it’s not an editor thing.
I know you don’t know me, but I used to be in tech support, so I DO try and run the gamut on things I could have missed.
And not that I don’t appreciate the help but it feels like I am spinning my wheels when I just-really want to run around in some grass. 
Pretty sure this is 100% due to RT culling settings and should have nothing to do with Lumen. Disabling Raytraced Shadows in the project settings will do nothing if the directional light is set to override this - so make sure this isn’t the case. Change the directional light to disable RT (or use project settings if RT shadows are disabled at project level), or make adjustments to your culling cvars.
Default RT Shadows:
Oh that was one thing I forgot to check or mention in my previous posts: I don’t use raytraced shadows, because they have a ton of annoying limitations, I only have “use HWRT for lumen” enabled for better lumen.
All hail the Banana-man…
It seems I DID enable ray-traced shadows on the project; been looking at this so long I missed it.
RT shadows enabled, It DOES seem related to culling/culling-distance. r.RayTracing.Culling.Radius 500000 works, but up close it’s still fugly, check the front of the mountain in the foreground.
Even with r.RayTracing.Culling 0, just-having RT shadows enabled still looks ugh (and seems counter-intuitive based on the settings?):
With RT shadows disabled at the project-level:
So, my take-away here is that one cannot really (effectively) use ray-traced shadows from the sun. I was able to enable RT shadows in the project but disable in UDS…
Thank you both for your help.
RT shadows also have “overlapping” issues with Nanite (Nanite landscape?). You could also try cvar nanite mode 1, but it’s very performance demanding and it doesn’t eliminate all overlapping issues.
In summary: I would never use RT shadows as they seem abandoned. Use VSMs or MegaLights instead.
i just rebuilt that scene. my question is why capture all this rvt stuff and duplicate it as this virtual heightfield? i guess it’s useful for things like snow or sand where the clipping is desired but the displacement can be done with the landscape itself, plus the material collision update. and… seems highly unstable in 5.5.2. atleast on my craptop. crashes when viewing the virtual wireframe and it just crashed with a vt feedback error.
either way… none of this is relevant to lumen. raytracing shadows is it’s own tech. i dunno how the terrain is raytraced anyway. is it a giant cluster/chunk collection of bvh? i mean… without any adaptive tesselation or dynamic deformation it’s just a bunch of triangles that don’t need to move. static bvh data. could be rather easy to raytrace against a sun lamp. for sure is alot worse with loads of foliage.
offtopic note 2: editor likes to crash on close or restart occassionaly. not sure why. but it’s an outro not inbetween. : )
Yeah - ray-traced sun shadows are definitely problematic with distant terrain and nanite at the moment.
My current preference is for VSM sun shadows with distance field shadows enabled for far away, non-nanite objects, and MegaLights for local lights. We’ll see how things go once MegaLight ms supports directional lights.
I don’t understand why HW RT shadows disables Distance Field Shadows though. Would be nice if they could take over for distant, culled geometry.
My editor always “crashes” when it’s closed too.
raytracing uses bounding boxes and geometry clusters aka bvh, while sdf is raymarching in basicly screenspace. combining those is i’d guess rather expensive or maybe not compatible. cause screenspace and bvh don’t share data. or you would raytrace in world space and if you hit a bounding box of a sdf volume you would start to raymarch. not sure if this is applicable or if shaders can switch that style of code. i’m not that deep in the engine. i can visualize it, but not code it very well, beyond hobby level. : )
If you’re deadset on using HWRT shadows, there actually is a semi-decent alternative to distance field shadows: far field. Though you have to use world partition and HLOD, if I’m not mistaken, since it samples a lower LOD for the far field traces. Also, it’s an opt in feature per mesh, so you can pick which things you want the far field to operate on.
If I understand correctly this is direct lighting using ray traced shadows leaking, so not really Lumen.
Most likely it’s due to ray tracing culling removing distant stuff from the BVH. Check out Ray Tracing Performance Guide in Unreal Engine | Unreal Engine 5.5 Documentation | Epic Developer Community to understand how to configure it. You can also use RT (or Lumen) visualizations to see whether BVH contains that Landscape in the distance.
Initially we had RT culling disabled, but people complained about poor RT performance, so now it’s enabled with some reasonable default settings.
Are there any plans to implement it for Megalights too in the near future?
hey, there is a way to cull RT shadows with intensity instead pop?
