Static Meshes that are reimported with less materials can lead to map check errors on instances that had overriden materials that require manual cleanup

UE - Rendering Architecture - Feb 5, 2025

StaticMeshActors placed in the world can override the default materials of a static mesh. If the static mesh is then reimported with less materials, the actors maintain references to unused material ...

FLevelInstanceActorGuid::GetGuid issue in Multiplayer

UE - World Creation - Worldbuilding Tools - Level Instances - Feb 3, 2025

I am doing some runtime manipulation of data layers and I am running into a check failure due to a zero guid in FLevelInstanceActorGuid::GetGuid during multiplayer testing. When I debug FLevelInsta ...

Spline mesh crashing in FRayTracingDynamicGeometryCollection::AddDynamicMeshBatchForGeometryUpdate

UE - Graphics Features - Ray Tracing - Jan 31, 2025

A crash occurs when using ray tracing with spline meshes preceded by the following ensure : Ensure condition failed: NumCPUVertices <= VertexBufferNumElements  File: Engine\Source\Runtime\Renderer\ ...

Lumen ignores Landscape Holes (Landscape Visibility) when Hardware Ray Tracing is enabled and Ray Lighting Mode is set to Surface Cache

UE - Graphics Features - Ray Tracing - Jan 31, 2025

Context Lumen is the default global illumination and reflections system. Lumen renders diffuse interreflection with infinite bounces and indirect specular reflections in large, detailed environments ...

In -game in Editor, if streaming-in a LevelInstance and initialize its world partition, then leaving that cell and make it go outside the streaming grid, to re-enter it again, will trigger a check(!StreamingPolicy) if no GC has happened during that time.

UE - World Creation - Worldbuilding Tools - World Partition - Jan 27, 2025

This crash can be fixed by adding a couple of || IsRunningGame() like it is done here:    FGenerateStreamingContext Context = FGenerateStreamingContext()        .SetLevelPackagesToGenerate((bIsPIE ...

UEditorEngine::AddPendingLateJoinClient checks original PIE/SIE state, not current state

UE - Networking - Jan 27, 2025

When adding late joining clients, the engine checks the originally requested EPlaySessionWorldType, rather than checking whether or not the session is currently simulating or not. This means if the ...

MRQ - Skeletal Mesh motion vector are output only for the last sample of Spatial Sample Count

UE - Anim - Sequencer - MRQ - Jan 24, 2025

Skeletal Mesh motion vectors are output only for the last sample of Spatial Sample Count, while Static Mesh motion vectors are output in all samples. UDN: [Link Removed] Slack thread: [Link Remo ...

Steam Sockets cannot create listen socket during non-seamless server travel

UE - Online - Jan 24, 2025

This seems to occur because the original listen socket is still around when the instance tries to create the new one, even though it has been marked for deletion. The issue does not occur when FStea ...

Temporal Super Sampling flickering temporal analysis visualisation mode indicates temporal analysis disabled for all objects on screen

UE - Graphics Features - Jan 24, 2025

This can also be observed while running in PIE mode using the console command "r.TSR.Visualize -2". It is not clear whether it is only the TSR flickering temporal analysis visualization that is exh ...

When a TSoftObjectPtr pointing to a const type is used as a parameter for a Dyanmic delegate, unreal marks it as deprecaded.

UE - Foundation - Cpp Tools - UnrealHeaderTool - Jan 21, 2025

A change has been done to the TSoftObjectPtr class that warns when constructing a pointer-to non-const from a pointer-to-const. This change makes sense and is correct. Example: UTexture2D* Loade ...