How does World Partition deal with actors that are always on grid cell bounds?

Development World Creation
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1

Hello everyone,

We recently started using WorldPartition in version 5.3.1. With the help of the wp.Editor.DumpStreamingGenerationLog command, we noticed a handful of actors that should have been in grid level 0 were promoted to the highest grid level.

We traced this issue back to the following function:

FSquare2DGridHelper GetPartitionedActors
if (GridLevel.GetNumIntersectingCells(ActorSetInstance->Bounds) == 1)

Using WorldSettings.bPreviewGrids, we realized that the actor is always intersecting two cells at once, regardless of the grid level.

Because the actor is so small, this specific case can be resolved by enabling wp.Runtime.RuntimeSpatialHashPlacePartitionActorsUsingLocation.

Alternatively, we could disable wp.Runtime.RuntimeSpatialHashUseAlignedGridLevels, but we are unsure of the potential side effects. I am not sure why this was defaulted to true or why it was ever needed. It would be helpful to get some information on both of these CVars.

Thanks