ISM lag spike when adding a single new instance after generation

Hello All,

So I’m working on a Minecraft-like game with voxel procedural generated landscapes. To generate the landscapes im using instanced static meshes for each type of block. I’m able to generate a 64x64x256 chunk with almost no lag and while playing I’m able to spawn new chunks without lag. However, when I go to add a single block to one of the chunks I get a second of jittery lag.

To place a block I raycast from blueprint to get the ism component and the impact location. Then i call a c++ function which just takes the location and runs the ISM->AddInstance() function.

void AChunk::PlaceBlock(FVector location)
	FTransform trans;
	trans.SetLocation(location - GetActorLocation());

I haven’t found any answers that have solved this lag issue so far, and reducing the chunk size does not seem to effect the lag amount. (16x16x256 was tried).

I’ve also added UPROPERTY(VisibleDefaultsOnly) to my ISM declarations and tried running it as standalone without any effect.

Any ideas would be greatly appreciated!
Thank you.