Merging negative-scaled actors breaks materials

UE - World Creation - Worldbuilding Tools - HLOD - Mar 27, 2018

Materials are broken when merging a mesh with another that has negative scale Licencee states that bisMirrored in FMeshMergeHelpers::TransformRawMeshVertexData seems to be involved. Does not occur ...

Distance Field Shadows Not Working On Large Objects

UE - Graphics Features - May 10, 2018

UDN Licensee reported this on 4.16, and I can repro in 4.17- 4.19.  Per Licensee: I'm trying to use distance field shadows on very large objects, but it looks like it does not work. Can you sugge ...

Adding a camera cut track through sequencer scripting does not set the movie scene's camera cut track

UE - Anim - Sequencer - Mar 13, 2020

When adding a camera cut track through sequencer scripting there is no way to set the camera cut track on the movie scene, which is how the add track menu determines if a new one can be added. This ...

BlackboardComponent observer can be called for the wrong key

UE - AI - BehaviorTree - Feb 7, 2023

We need to, at least, prevent this by clearing observers when running a new BT using a different blackboard. Must also think that this might affect licensees relying on the current behavior (might h ...

TranslucentVolumeAmbient is darkened in InjectTranslucencyLightingVolume pass when using VSMs with r.Shadow.Virtual.ForceOnlyVirtualShadowMaps is Off

UE - Graphics Features - Shadows - Nov 18, 2024

CSM targets are still created and affect the InjectTranslucencyLightingVolume pass when moving in a project that only uses VSM causing over brightening of fog planes and other translucent meshes. r ...

Compiling any material in UE 5.5.1 without ShaderCompiler JobCache results in a crash

UE - Rendering Architecture - Shaders - Jan 15, 2025

Compiling any material with r.ShaderCompiler.JobCache=0 causes ShaderCompileWorker to crash. Reproduction steps cause a crash during Editor startup, but this bug may affect other scenarios where mat ...

Popping Ribbon UVs

UE - Niagara - Mar 10, 2025

Please see the Additional Link for related UDN information. The UV popping described can be subtle, depending on settings; it's affected by spawn rate and GPU vs CPU. The popping shown in the gif t ...

Niagara Fails to Compile Shader For iOS and Android

UE - Niagara - Aug 2, 2018

Niagara fails to compile shader for iOS and Android. Unable to test in 4.19 due to assets provided being created in 4.20. Found in 4.20 CL# 4233996 and 4.21 CL# 4247867 ...

Editor primitives render incorrectly in stereoscopic with instanced stereo

UE - Platform - XR - Aug 17, 2016

Trigger box icons move around when oculus head movement is used. Found in //UE4/Release-Staging-4.13 @ 3090357 QA-Promotion map Edit: 08-22: This affects volumes as well as their editor icons, upd ...

Using Blend Physics Weight causes skeletal mesh to spin at high speed

OLD - Anim - Mar 5, 2015

When Phyics Blend in the PHAT editor is set between 0 and 1, the user character will spin wildly. User has image of this affecting character in game whereas I was only able to replicate it in the PH ...