Unreal Engine Issues
Unreal Engine Issues
Unstable automation tests in "Standard Tests" list.
UE - Simulation - Core - Feb 20, 2026The two following automation tests found in the "Standard Tests" list hit exceptions & cause the editor to crash:System->Physics->Interface->BodyInstanceShaders->ShaderPreprocessor->BuiltInMacros ...
bWeldSimulatedBodies not replicated with attachment
UE - Simulation - Core - Jan 13, 2026The bWeldSimulatedBodies attachment parameter is not replicated to clients, both in USceneComponent's attachment replication handling and in AActor's FRepAttachment struct. If AttachToComponent is c ...
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 ...