Unreal Engine Issues
Unreal Engine Issues
Unable to interact or collide with geometry collection after Removal on Sleep or Break timer finishes, yet unbroken piece continue to render
UE - Simulation - Core - Dec 18, 2025Context: 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 ...
Convex hull generation fails when first 3 verts are colinear
UE - Simulation - Core - Dec 9, 2025The licensee identified a number of cases where loading assets will trigger convex hull generation warnings:If the first 3 verts in the set are colinear (in which case IsPlanarShape() returns true b ...
Chaos sometimes can not generate contact points while two dynamic convex hulls actually collide. It results in instability in the contact behavior - such as jittering, inconsistent contact forces, or unexpected collision responses.
UE - Simulation - Core - Dec 2, 2025Context: Chaos Physics is able to use convex hulls to represent object collision geometry for queries and simulation. Problem: Chaos sometimes can not generate contact points while two dynamic conv ...
Not all MidPhases are enumerated in TSimCallbackObject::OnMidPhaseModification
UE - Simulation - Core - Dec 2, 2025Newly generated MidPhases are copied into the array accessible in the NarrowPhase after the OnPreSimulate callback is invoked. As a result, it is not possible to modify newly created MidPhases withi ...
Not all MidPhases are enumerated in TSimCallbackObject::OnMidPhaseModification
UE - Simulation - Core - Dec 2, 2025Newly generated MidPhases are copied into the array accessible in the NarrowPhase after the OnPreSimulate callback is invoked. As a result, it is not possible to modify newly created MidPhases withi ...
BoxOverlapActors fails to catch an Overlaped actor with a particular scale, from a particular position
UE - Simulation - Core - Sep 30, 2025BoxOverlapActors fails to overlap a scaled Floor actor with a particular scale, from a particular position and extent. The setup is really specific and described in Steps to Reproduce. The required ...
Wrong density calculation in UBodySetup::CalculateMass
UE - Simulation - Core - Sep 29, 2025Wrong density calculation in UBodySetup::CalculateMass. The licensee has provided the following analysis and suggested fix: In UBodySetup::CalculateMass, the following code is present: // physical ...
Typo in GetAsBoundsArray() from file AABBTree.h on Chaos module
UE - Simulation - Core - Jul 30, 2025From file [Engine\Source\Runtime\Experimental\Chaos\Public\Chaos\AABBTree.h], function Chaos::TAABBTree<>::GetAsBoundsArray(): bool GetAsBoundsArray(TArray<TAABB<T, 3>>& AllBounds, int32 NodeIdx, i ...
Soft angular constraints solve velocity like hard constraints
UE - Simulation - Core - Jul 17, 2025Soft angular constraints are solving velocity like hard constraints. Instead of swinging back and forth, the affected body just snaps to 45 degrees. Check the steps to reproduce for more details. Th ...
Non-Nanite Instanced Static Mesh Collision not showing in collision view
UE - Simulation - Core - Apr 3, 2025This issue is the same as [Link Removed], but it causes confusion for developers because only Nanite ISM are rendered correctly since UE5. . ...