Unreal Engine Issues

Translucent materials in the PostMotionBlur pass can cause a flickering viewport artefact when using TAA

There appears to be a bug relating to rendering multiple windows that can trigger under unknown circumstances. It has been reported on rectangle lights in the forums and on PostMotionBlur materials ...

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

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 ...

Parameters are not copied and when copy pasting a child actor component of an actor to another actor.

FLevelInstanceActorGuid::GetGuid issue in Multiplayer

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

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

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 ...

No warnings or errors if a UEnum has Bitflags metadata, but no Flags flag.

The problem here isn't obvious: the native enum, EAnotherEnum, is missing the Flags flag for the UEnum. As a result, K2Node_GetEnumeratorNameAsString returns the max enum when it gets a combined fla ...

Bitmask ints can't be converted to strings

While we do have an auto cast function that handles an int to string conversion, bitmask ints use a "bitmask" subcategory which thwarts are ability to find the cast function. ...

K2Node_GetEnumeratorName doesn't support bitmasks

This is almost identical to [Link Removed]. The difference is that we need a variant of UEnum::GetNameByValue that supports bitmasks. We'll likely have to run this by Core. ...

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.

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