Summary
Changing a material’s Blend Mode crashes the editor when that material is currently assigned to a Nanite-enabled static mesh (visible in the level or in the Material Editor preview). The engine correctly logs a warning that the blend mode is unsupported on Nanite, but then proceeds into a Lumen scene card capture path that asserts instead of failing gracefully.
What Type of Bug are you experiencing?
AI
Steps to Reproduce
Create or use a static mesh with Nanite enabled.
Assign a material to it (in the level, or set as the Material Editor’s preview mesh).
Open the material and change its Blend Mode.
Editor crashes immediately.
Expected Result
Editor should not crash. Ideally it should block or gracefully reject the invalid blend mode/Nanite combination, consistent with the warning it already logs.
Observed Result
Editor crashes with an unhandled assertion.
Affects Versions
5.8
Platform(s)
Windows
For crash reports, include your callstack
LogStaticMesh: Warning: Invalid material [NewMaterial] used on Nanite static mesh [SM_Drone_Two_Mats].
Only opaque or masked blend modes are currently supported, [BLEND_TranslucentColoredTransmittance] blend mode was specified.
LogWindows: Error: appError called: Assertion failed: Nanite::IsSupportedBlendMode(ShadingMaterial)
[File:D:\build++UE5\Sync\Engine\Source\Runtime\Renderer\Private\Lumen\LumenSceneCardCapture.cpp] [Line: 312]