World Partition: Making sense of Spatially / Non-spatially loaded definitions and errors

Example error:

Non-spatially loaded actor TCS_RoadIntersection5 references Spatially loaded actor TCS_RoadPath 7

Documentation:

Is Spatially Loaded Determines if the Actor is spatially loaded:

  • If enabled, this Actor is loaded when in range of any streaming source when not assigned to a disabled Data Layer.
  • If disabled, this Actor is loaded when not assigned to a disabled Data Layer. Documentation URL

Why is UE5.0.1 complaining about spatially loading?
What is spatially loading?
What is a streaming source in the context of World Partition and Actors?

The documentation make it sound like World Partition Actors only load when assigned to a disabled data layer.

Above error may produce when assigned connected blueprints have a different HLOD setting.

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I also wondering this topic too. Anyone to help?

in outerliner

AParentActor ( Is Spatially Loaded : NoChecked )
± AChildActor ( Is Spatially Loaded : Checked )

It happens in this situation

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Uh…what?

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The error says that an actor cannot reference or be referenced by another actor if one of them has the Spatially Loaded Actor check. Spatially loaded actor means that if the actor is inside a cell that is unloaded the actor will be unloaded too, but if that actor is reference by another actor that is not unloaded and uses it, can cause a crash.

A streaming source actor is and actor that loads a world partition cells in runtime (the player is by default a streaming source actor, so that when the player moves, the level cells will load/unload depending of his range)

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Example: I had a terrain object that was in the “Landscape” folder in the Outliner, so if I toggled the visibility of the landscape (non spatially loaded) it would also make the terrain object (spatially loaded) invisible in the viewport, I just dragged the terrain object out of the Landscape folder so it’s not dependent on it anymore.