# Lightmass crashed fatal error 

**URL:** <https://forums.unrealengine.com/t/lightmass-crashed-fatal-error/2853051>\
**Category:** Issues and Bug Reporting (Unreal Engine)\
**Tags:** unreal-engine, bug-report, editor, question\
**Created:** [November 9, 2026, 9:13pm UTC](https://forums.unrealengine.com/t/lightmass-crashed-fatal-error/2853051 "2026-11-09T21:13:46Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Alexanderfall](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Alexanderfall](https://forums.unrealengine.com/u/Alexanderfall)\
**Post date:** [November 9, 2026, 9:13pm UTC](https://forums.unrealengine.com/t/lightmass-crashed-fatal-error/2853051/1 "2026-11-09T21:13:46Z")

</div>

### Summary

after changing the max shadow resolution with the console command r.Shadow.MaxResolution whenever i try to build the lighting i get the error:  
=== Lightmass crashed: ===  
Fatal error: [File:D:/Build/++UE4/Sync/Engine/Source/Programs/UnrealLightmass/Private/Lighting/LightingSystem.cpp] [Line: 1458]

### What Type of Bug are you experiencing?

Editor

### Steps to Reproduce

unknown

### Expected Result

unknown

### Observed Result

cannot bake shadows

### Affects Versions

4.27

### Platform(s)

Windows

### Upload an image

 ![Screenshot 2026-11-07 170339.png](https://d3kjluh73b9h9o.cloudfront.net/original/4X/9/6/a/96a104a34ee4e0cb2bf3d10b3f8168342941c682.png) ![Screenshot 2026-11-07 170329.png](https://d3kjluh73b9h9o.cloudfront.net/original/4X/6/4/8/6482161f6cdc3e857afea475d4fc86f25b605a41.png)

### Additional Notes

i tried verifying the engine through epic games launcher and clearing the swarm agent cache and it still won’t work.

for some reason it only fails on the medium quality setting when baking lighting.