Description

Context:
A static mesh is able to have a geometry collection generated from it using the Fracture editing mode. It can be fractured in many different ways, and when acted upon by a chaos field agent or other such break impulses during PIE it will break into pieces as determined by how it was fractured. If removal-on-break parameters or the remove on sleep on the geometry collection is set to true, the broken pieces disappear after the set timers run out.

Problem:
If a geometry collection is not completely destroyed when broken, and the removal on sleep or removal on break timer are allowed to finish (the broken pieces disappear completely) before attempting to break the collection further, the rest of the geometry collection is unable to be interacted with, yet continues to render.

Expected:
The geometry collection should be able to be interacted with further, either by collision or by being able to be broken further.

Steps to Reproduce

Repro project (Internal only):
1. Open attached project
2. Start PIE
3. Tap "E" while aiming at "GC_Cube" for trace hit and destruction
4. Note the destroyed pieces disappear due to Removal on Break
5. Tap "E" again after pieces fully disappear while aiming at "GC_Cube"
6. Note trace does not hit the cube, the GC does not break further, and player character is able to walk through the unbroken pieces that are still rendering
7a. This is repeatable if removal on break is set to false, and removal on sleep is set to true
7b. Enable Remove on Sleep on the rest collection to note similar behavior
8a. Observed: Rest of the GC is still rendered, but the player can no longer collide with the remaining pieces
8b. Expected: GC is able to be destroyed further or collided with

Fresh project:
1. Start a fresh 5.7.1 First Person project
2. Create a cube static mesh actor, and scale it to approximately x=0.3, y=5, z=3
3. Tap Shift+6 or choose Fracture Mode in the Select Mode drop-down
4. Select the newly created cube, and click "New" in the top-left of the Fracture menu under "Generate"
5. Click "Create Geometry Collection" on the new menu that opens
6. Select "Uniform" under "Fracture"
7. Set Minimum and Maximum Voronoi Sites to 200 under Uniform Voronoi, then click "Fracture" at the bottom of that menu
8. Select "Intrctve" under "Select", and click and drag to select the top row of pieces that were generated for the geometry collection
9. Under Fracture Hierarchy tab, right-click any of the newly selected pieces, hover over "Anchored" and select "Yes" to anchor the top row of pieces that are a part of the geometry collection
10. Under "Utilities" back in the Fracture Mode menu, select "Set removal-on-break parameters" (trash can icon)
11. Set the four Post Break and Removal Timer parameters to 0.1
12. Select the entire geometry collection from the Fracture Hierarchy tab by shift left-clicking the top piece in the list to the bottom piece
13. Click "Apply removal-on-break parameters" to apply the timers to the pieces
14. Ensure "Allow Removal on Break" is set to true the in asset's parameters in the Details tab
15. In the content browser, navigate to the Engine/EditorResources/FieldNodes folder, and place a FS_MasterField in the level
16. Position this field so that the upper half of the sphere touches the bottom of the geometry collection you've created
17. Start PIE, and note the destruction of the GC
18a. Observed: Rest of the GC is still rendered, but the player can no longer collide with the remaining pieces
18b. Expected: GC is able to be destroyed further or collided with
19. This behavior also occurs if "Allow Removal on Break" is set to false, and "Allow Removal on Sleep" is set to true in the Details tab of the asset
20. Under "Chaos Physics" in the Details tab, double-click the "Rest Collection" asset to open the created geometry collection
21. Select "Continue without Dataflow", then under "Removal" in the next menu, set "Remove on Sleep" to true, setting the "Sleep Min Max" values to 0.1 and 1.0
22. Repeat the process of PIE, and note similar behavior to Removal on Break
23a. Observed: Rest of the GC is still rendered, but the player can no longer collide with the remaining pieces
23b. Expected: GC is able to be destroyed further or collided with

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Unresolved
ComponentUE - Simulation - Core
Affects Versions5.7.1
CreatedDec 18, 2025
UpdatedDec 19, 2025
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