I noticed that lumen reflection for HISM (Hierachical Instanced Meshes) are black!
The weird thing is ISM is working pretty much fine with lumen
Is this a limitation for HISM with lumen scene?
That’s quite a strange effect you are getting, as HSIM should be supported by Lumen with no issues. Maybe their surface cache is being culled in scene. Still, as ISM work as intended, mesh and distance should be fine.
I would start by comparing settings between your HSIM and ISM settings, specially Lighting and Rendering settings, check that their values allign, or are at least close by. Also, check your PPV and rise the value for “Lumen Scene Detail” (around 2 or 3), to ensure your objects are not being culled.
Another possible test, would to open a clean project, and add both HISM and ISM components with a simple mesh, and the same instance placement, then compare in Lumen Scene view. If the issue doesn’t appear here, then it’s tied to an element in your project.
For further details on the Lumen support, please check the related UE doc:
I tested it out on a empty project (5.8), with all the PPV settings you recommended and some more cvar to increase the lumen scene distance (Including Raytracing Cull distance) and the result is sadly the same
It works with nanite pretty ■■■■ well, that’s a good sign. seems like that HISM doesn’t work well with lumen on a Non-Nanite projects though. Or maybe this potentially to be just a bug? I hope it does! or I might just miss something-
Interesting, HSIM is still getting culled in the empty test project. That means nothing is inherently wrong with your own project. ISM still works as intended, and Nanite serves as a workaround. So, it’s quite possible that we are dealing with a specific bugged interaction between HISM and non-Nanite meshes. Just for further testing, I would try the following:
Temporary set your BP’s scale to a fixed value (like 1.1.1), and check if the culling keeps happening
Try the other options from Ray Lighting Mode, and see if they alter the meshes’ behaviour
It’s me again!
Yes I just tested it again, I removed any scaling on the BP and the instances to the default (1.1.1) Scale and tried changed to other big non nanite meshes and fiddle around with the settings (HWRT Lumen, Ray lighting mode, Software Raytracing mode) Sadly the result is still the same… The HISM still culled in the lumen scene and ISM still working fine.
I was wondering on why the scene was so dark and found out the culprit was this issue! I tried to changed it into ISM and got hit by reality that my solution was slower than Unreal Engine solution (HISM), Im looking forward for a fix.
