Issue with HISMC (LOD switched for all instances same time)

Development Rendering
1

Greetings. I’ve tried to implement HISMC. But it acts like ISMC. LODs are switched for all instances at once.
Here’s video: https://i.gyazo.com/7b1b0ef4f79c42d5…d96b65de2d.mp4
For some reason can’t upload a video here (same issue with it as on Answerhub, no mp4 allowed).
It’s the same on 4.21 and 4.23.

Thank you in advance.

Mirror question on Answerhub: https://answers.unrealengine.com/que…tances-sa.html

2

It should work, but AFAIK LODs on HISMC are switched in clusters, rather than individually. I may be wrong, but it would be worth testing on some more random distribution of the instances.

3

Yeah, that’s correct. They are likely so close to each other that all the instances are in the same cluster.

4

Any way to define the size of the cluster? I prefer lods swapped at least in half of the distance.

5

People from UnrealSlackers Discord helped a lot.



int32 UHierarchicalInstancedStaticMeshComponent::DesiredInstancesPerLeaf()
{
    int32 LOD0Verts = GetVertsForLOD(0);
    int32 VertsToSplit = CVarMinVertsToSplitNode.GetValueOnAnyThread();
    if (LOD0Verts)
    {
        return FMath::Clamp(VertsToSplit / LOD0Verts, 1, 1024);
    }
    return 16;
}

Setting CVAR


foliage.MinVertsToSplitNode

To a lower value will shrunk the cluster’s size.
Don’t forget to rebuild your HISMC to update the result.

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