Unreal Engine Issues
Unreal Engine Issues
In 5.6, bWarningsAsErrors does not work with clang
UE - Foundation - Cpp Tools - UnrealBuildTool - Sep 20, 2025In 5.6, many warnings and errors specify their command line arguments to the compiler with these new C# attributes: [WarningsClangToolChain(["-Wno-date-time"], ["-Wdate-time", "-Wno-error=date-ti ...
Ray tracing scene doesn't reflect WPO with instance custom data
UE - Rendering - Graphics Features - Ray Tracing - Sep 19, 2025When custom instance data is used to calculate WPO in a Material and applied to an ISM the WPO value in the Lumen scene (ray tracing scene) is different than the visible scene resulting in incorrect ...
Nanite Skeletal Meshes Invalidate VSM
UE - Rendering - Graphics Features - Nanite - Sep 17, 2025Nanite Skeletal Meshes will always invalidate VSMs, even with their Shadow Cache Invalidation Behavior set to Rigid. This does not match the behavior of non-Nanite Skeletal Meshes. ...
Controller::OnPossessedPawnChanged broadcasts (Pawn->null) but not (null->Pawn) during AGameModeBase::RestartPlayer()
UE - Gameplay - Sep 17, 2025Context AController has a blueprint assignable delegate that fires when the possessed pawn changes. This should fire in both singleplayer and networked games. The bug is reproducible in single play ...
Hovering items at bottom right of Content Browser does not display tooltip and causes cursor flicker
UE - Editor - Developer Usability - Sep 17, 2025When hovering over items located at the bottom right corner of the Content Browser while the Editor is maximized, the tooltip is not displayed. It seems that the tooltip would extend beyond the edge ...
Switching modular control rig to FK mode breaks pose of controls that have been baked to rig
UE - Anim - Rigging - Control Rig - Sep 14, 2025From the licensee:We have built a modular Control Rig in Unreal 5.6, and while IK to FK matching works correctly inthe rig, but we are facing an issue when applying mocap animation to the characters ...
SkyLight Leaking does not affect reflections when the SkyLight is static but static lighting is disallowed
UE - Rendering - Graphics Features - Sep 10, 2025Reflections do not receive SkyLight leakage contribution from a static SkyLight when static lighting is disallowed. This is caused by the function UpdateSkyIrradianceGpuBuffer checking if the SkyLig ...
Importing FBX that contains a socket from Blender to Unreal, the socket gets rotated by 90° and is scaled by 100
UE - Editor - Content Pipeline - FBX - Sep 9, 2025Context: Sockets are attach points that can be placed on a Static Mesh to attach an object to the static mesh. Problem: Importing an FBX that contains a socket from Blender to Unreal, the socket ge ...
Lumen Translucency lighting vs opaque mismatch is larger than expected
UE - Rendering - Graphics Features - Lumen - Sep 5, 2025The licensee's VFX team has been struggling with getting their Niagara systems with translucent materials to fit into the environments they are being used in. In a project with default settings, the ...
Cook non-determinism when serializing UObject pointers pointing to garbage
UE - CoreTech - UObject - Aug 25, 2025There's a cook determinism issue in the way UObject unversioned serialization handles UObject pointers pointing to garbage. Depending on GC timing, it can either be skipped (as a property matching C ...