Unreal Engine Issues
Unreal Engine Issues
Foliage painted on Mesh Terrain disappears after edits are made
UE - Graphics Tools - Mesh Terrain - Sep 22, 2026Mesh Terrain recreates the visible section actors when edits are made, and those sections in the editor don't correspond to the ones at runtime, which breaks the ComponentId that the foliage system ...
Enhanced Input: use-after-free in EvaluateInputComponentDelegates when a delegate forces a synchronous mapping rebuild
UE - Gameplay - Input - Sep 21, 2026Context UEnhancedPlayerInput::EvaluateInputComponentDelegates iterates the delegates that triggered this tick. For each one it resolves the action's state via FindActionInstanceData(DelegateAction) ...
ReturnUntouchedSceneColorForPostProcessing ignores view overrides and breaks splitscreen
UE - Rendering - Architecture - Sep 17, 2026When a view extension uses ReturnUntouchedSceneColorForPostProcessing and uses split screen, the final view is incorrect (clipped) because ReturnUntouchedSceneColorForPostProcessing doesn't take int ...
Open Formats: USD UX - Visibility managemente in USD Stage Actor
UE - VEI - Open File Formats - Sep 15, 2026Working with a big USDStageActor is complicated due to visibility management. We are importing "simple" environments from usd files through the USDStageActor. However, when the artist wants to hide ...
Race condition in GetFunctionSig_Write() and other function signatures
UE - Rendering - Architecture - Niagara - Sep 11, 2026A race condition exists in GetFunctionSig_Write() and other places where FNiagaraFunctionSignature is lazily initialized because multiple worker threads can progress past if (!Sig.IsValid()) and st ...
TMap where key is an FString: initializer list will accept bad MakeTuple
UE - Core - Systems - Sep 2, 2026POST LINK: https://forums.unrealengine.com/t/tmap-where-key-is-an-fstring-initializer-list-will-accept-bad-maketuple/2747443 POST BODY:Summary A TMap where the key is an FString can be created lik ...
ShouldMarkSyncPhases causes pose discontinuities when sync leader changes
UE - Runtime - Anim BP - Aug 27, 2026The issue is caused by the way that we calculate the leader sample's Time vs the follower sample’s Time and how that calculation switches on the frame when a follower sample becomes a lead sample. ...
Cannot get Texture Size property from Texture Collections
UE - Rendering - Architecture - Materials - Aug 26, 2026The following error is shown when attempting to use the Texture Size of a Texture Collection texture object: Texture size only available for Texture2D, TextureVirtual, Texture2DArray, VolumeTexture ...
HasVertexPositionOffsetConnected returns true even if WorldPosition output isn't connect to output
UE - Rendering - Architecture - Materials - Aug 25, 2026FMaterialCachedExpressionData::UpdateForExpressions iterates on all expressions, even for those that are not enabled in a material instance or not even connected to output. This will enable features ...
MID TextureCollections don't work with Post Process Overlays
UE - Rendering - RHI - Aug 24, 2026TextureCollectionParameters in a material assigned to a Post Process Overlay are not overridden by a MID because CopyInterpParameters in Engine\Source\Runtime\Engine\Private\Materials\MaterialInsta ...