Unreal Engine Issues
Unreal Engine Issues
Null Material Layers in Material Instances cause Opacity Mask and WPO to break on Nanite Meshes
UE - Rendering Architecture - Materials - Oct 31, 2024When a Material Instance is loaded that has a nullptr layer in StaticParametrs.Materiallayers. The Material Instance will create it's own CachedExpressionData but the ConnectedParameterMask will be ...
Ensure condition failed / Crash on BP Compile after adding variable
UE - Gameplay - Blueprint Compiler - Jan 26, 2018Crash when compiling BP (containing user defined struct + object reference) after adding variable. ...
No Dynamic Shadows From Stationary Lights in Forward Shading Without Building Lighting
UE - Graphics Features - Apr 24, 2018I've observed this issue in 4.18.3 and 4.19.1. Per Licensee: So we've spotted an issue that I wanted to put on your radar with dynamic shadowed stationary lights + r.ForwardShading=1 What we're s ...
Tabbing out of exclusive fullscreen leaves the window & backbuffer in an incorrect state
UE - Editor - UI Systems - Apr 24, 2020With windows 10 there has come some new swap chains, which unfortunately messes some things with regards to fullscreen up. We've fixed a bunch in the renderer (which would downright cause crashes), ...
Editor Crash when trying to get Color data from Vertex buffer
UE - Graphics Features - Nov 6, 2019When attempting to get the vertex color of an instance of of a static mesh that is painted after placing it in the World Viewport. The Editor crashes returning an "Unhandled Exception". The cause o ...
Preview Rendering Levels Do Not Display Supported Optimization Viewmodes in Viewport Dropdown
UE - Platform - Mobile - Apr 2, 2019When attempting to set an optimization viewmode while using a Preview Rendering Level other than Shader Model 5, the Optimization Viewmodes dropdown is missing all of its options and instead display ...
PCG sampling of RVT does only works when sampling the first texture layer
UE - World Creation - Procedural Tools - PCG Component - Dec 11, 2025The logic for selecting a page table texture in FVirtualTexturePageTable::Initialize() uses the indexing for texture layers (index 0-7) to fetch from the page table textures (index 0-1). All RVT for ...
FString.Mid doesn't react appropriately when given negative values for the Count variable
UE - Foundation - Core - Jul 16, 2015If you use a 5 character string (hello) to call the Mid function and provide 0 for start, -1 for count, it'll give you the entire string. This should either return an assert or treat all negatives a ...
Crash when adding Actor Array Element to a Sequencer Event Struct
UE - Anim - Sequencer - May 25, 2017Crash when adding Actor Array Element to a Sequencer Event Struct Error message: Assertion failed: 0 [Link Removed] [Line: 56] Source Context: 42 N = FName(*StringName); 43 ...
Crash when changing r.MaterialQualityLevel when FastGeo plugin enabled in cooked build
UE - World Creation - Worldbuilding Tools - Sep 5, 2025The engine crashes when the r.MaterialQualityLevel is changed in a cooked game that uses the FastGeo Streaming Plugin. The crash doesn't repro with the same steps in Editor, just in a cooked build. ...