RailClone and Unreal Engine - Culling

[BK8837]

Hello Itoo Team,
I'm wondering if anyone on the Itoo team knows why this behavior occurs in Unreal Engine 5.5:

When I export a RailClone object using Datasmith and import it into UE, enabling ray tracing causes the object to exhibit some sort of culling behavior. However, when I switch to Lumen, the object appears correct. Since your team has experience with both RailClone and Unreal Engine, as shown in your YouTube video, I thought you might have some insight into this issue.

Please see the attached images. The objects in the distance become invisible and only appear when I get closer. While this behavior is generally desirable, I was wondering if there's a parameter that allows me to extend their visibility range. Thank you!

[Michal Karmazín]

Hi,

I'm sorry to hear you're experiencing trouble and thank you for bringing this to our attention. First, please note that Epic uses our APIs to support Forest Pack and RailClone — not the other way around — so we have limited control over how Datasmith exports our plugins. That said, one of our users recently reported a potential issue related to InstancedStaticMesh culling when using Ray Tracing. You might try disabling it via the console with the following command:

r.RayTracing.Geometry.InstancedStaticMeshes.Culling = 0

to see if there's any difference.

It might be related to the type of objects that Datasmith creates from Forest data. As mentioned here:

"When you use Datasmith to import or sync a 3ds Max scene that contains a Forest Pack or RailClone object in Unreal Engine, Datasmith creates a single Actor in the Unreal Engine Level, and names it according to the name of the object in 3ds Max.
Within the Actor, Datasmith creates the following for each type of geometry that the object handles:

• A Hierarchical Instanced Static Mesh (HISM) Component.
• A Static Mesh Asset in your Project content.

Datasmith then sets each geometry type's HISM Component to refer to its Static Mesh Asset.
...
The HISM Component is the same technology used in Unreal Engine's Foliage system. It's a very efficient way to render many instances of the same Static Mesh. The Unreal Engine renderer batches all instances managed by the same HISM Component, and makes a single draw call per Material assigned to the Static Mesh Asset. By using the HISM, the renderer can handle more instances without affecting GPU performance or frame rate."

Thank you in advance for any additional insights you can share regarding this issue, either with us or the user community — it may help others who encounter similar problems.

Best regards,

[BK8837]

Thanks Michael,
I would’ve never guessed that! I had pretty much tried everything, but the console command worked perfectly. Now RailClone objects are visible from far away. I came to the right place, Thanks!