Context:
Data Layers is a system within World Partition used to organize Actors both in the Editor and at runtime. It allows for the user to dynamically load and unload layers in the Editor to help manage complex worlds.
Problem:
The problem is UWorldPartitionSubsystem::IsStreamingCompleted returning the wrong query result when all cells and actors in location are in Data Layers.
Suggestion:
The licensee suggested the issue lies in following code (in WorldPartitionStreamingPolicy.cpp) where it will cause that cell to be skipped.
The licensee also notes "The function name and this block of code seem to be implying has streaming "settled"/"Finished" at that location, but the fact you can pass a query state in (including Unloaded) imply that we should be able to use the function as we're currently doing."
// Test if cell is already in the effective wanted state.
// Note that GetCellEffectiveWantedState always return Activated when the cell has no data layers.
// In this case, continue testing the QueryState with the CellState to respect bExactState.
if (!bSkipCell && Cell->HasDataLayers())
1.) Download and open repro project provided by licensee or the one uploaded in ticket
2.) Start Play in Editor
3.) Walk (W key) towards Red Sphere until it turns Green
Observe: Text in top left (Active) and Green Sphere. This indicates that the area at the sphere's location is Active and streamed in
4.) Walk away (S key) from Green Sphere until it turns red
Observe: Text in top left (Unloaded) and Red Sphere. This indicates that the area at the sphere's location is Unloaded and streamed out
5.) Exit Play in Editor
6.) In the Outliner, Pin the actor "DeleteThisCube" to force load it, then delete it by clicking on it and pressing the Del Key
7.) Start Play in Editor
Observe: The Sphere color flickering between Red and Green, and the text at the top left alternating between Active and Unloaded
Expected: Behavior should be the same prior to deleting the Cube (This cube is not part of any data layer)
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-306965 in the post.
1 |
Component | UE - World Creation - Worldbuilding Tools - World Partition |
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Target Fix | 5.7 |
Created | Jul 24, 2025 |
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Updated | Aug 12, 2025 |