Attempting to compile an editor plugin that spawns an instance of ACullDistanceVolume causes a linker error

UE - Gameplay - Aug 9, 2018

A linker error is encountered if an Editor plugin spawns an ACullDistanceVolume instance. This is caused by neither having ENGINE_API or MinimalAPI specified in its UCLASS macro. Regression?: No Th ...

Volumetric Lightmap Holes Appear Every Fifth Build

UE - Graphics Features - Sep 11, 2018

Volumetric lightmap holes appear every fifth build.  Found in 4.19 CL# 4033788, 4.20 CL# 4302132, and 4.21 CL# 4348893 ...

TestEqual(TCHAR*, TCHAR*) function is testing pointer equality instead of values

UE - Automation Test - Oct 1, 2018

A licensee has reported that the TestEqual(TCHAR*, TCHAR*) function tests for pointer equality instead of comparing two values, which does not accomplish what the function is meant to do. Regressio ...

GameplayTask classes that have a BeginSpawningActor function never call the Activate function

UE - AI - Oct 3, 2018

A class that inherits from GameplayTask which also has a BeginSpawningActor function will not have its Activate function fired properly. Removing this function causes it to fire properly. Regressio ...

RF_WasLoaded is set to False in PIE for instances of a Blueprint if the Blueprint is recompiled

UE - Gameplay - Blueprint - Apr 5, 2019

The RF_WasLoaded flag is set to false for Blueprint instances in PIE if the Blueprint is edited and compiled. This is fixed by saving the level which is a simple workaround but this should be needed ...

Cannot change Collision Profile of BP component instances

UE - Simulation - Physics - Oct 24, 2019

BP instances placed in level cannot have their components' collision profiles modified to anything other than default and custom. Note that this did not occur in 4.22 (after applying the separate ...

Niagara system loses source emitters when moving Engine from 4.22 or earlier to 4.23 or later.

UE - Niagara - Nov 29, 2019

The following code causes this behavior.// NiagaraSystem.cpp for (FNiagaraEmitterHandle& EmitterHandle : EmitterHandles) { EmitterHandle.ConditionalPostLoad(NiagaraVer); if (!EmitterHandl ...

Problems in skeletal mesh merge

UE - Editor - Content Pipeline - Asset Build - May 10, 2021

There are a few issues a licensee has found with the skeletal mesh merge operation. See the UDN for more details and the proposed fixes. Note, the issue with the cloth merge is already logged in a ...

bIgnoreAllPressedKeysUntilRelease only applies to keys in the previous mapping

UE - Gameplay - Input - Jun 16, 2022

This is because the RebuildControlMappings function only checks this flag when you have a mapping that was already added, we should apply this for any new mappings as well.  I'll update the repro s ...

Disabling bLerpUVs in Nanite Settings of Static Mesh causes texture warping in clusters

UE - Graphics Features - Nanite - Jan 21, 2025

The licensee has identified a potential fix by changing if( Settings.bLerpUVs ) to if( Settings.bLerpUVs || UVIndex == 0 ) On line 389 of NaniteBuilder\Private\Cluster.cpp in UE 5.5 ...