Lightmass Crashes

[2017.11.13-17.16.48:906][742]*** CRITICAL ERROR! Machine: RAILDEX
[2017.11.13-17.16.48:906][742]*** CRITICAL ERROR! Logfile: UnrealLight_RAILDEX_389D5A694AAE1799F7B6C9A432A12D78.log
[2017.11.13-17.16.48:906][742]*** CRITICAL ERROR! Crash report:
[2017.11.13-17.16.48:906][742]Job has failed! The task failure count is non-zero
[2017.11.13-17.16.48:906][742]LightingResults: Error: === Lightmass crashed: ===Unhandled Exception: EXCEPTION_INT_DIVIDE_BY_ZERO
Fatal error: [File:D:\Build++UE4+Release-4.18+Compile\Sync\Engine\Source\Programs\UnrealLightmass\Private\Lighting\LightingSystem.cpp] [Line: 1338]
Static lighting thread exception:

0x00000000DFF48F97 UnrealLightmass.exe!Lightmass::FStaticLightingSystem::IncomingRadianceAdaptive<Lightmass::TFinalGatherSample<2> >() []
0x00000000DFF67846 UnrealLightmass.exe!Lightmass::FStaticLightingSystem::CachePointIncomingRadiance() []
0x00000000DFFFD12A UnrealLightmass.exe!Lightmass::FStaticLightingSystem::ProcessCacheIndirectLightingTask() []
0x00000000DFFDA25C UnrealLightmass.exe!Lightmass::FStaticLightingSystem::CalculateIndirectLightingTextureMapping() []
0x00000000DFFFFE76 UnrealLightmass.exe!Lightmass::FStaticLightingSystem::ProcessTextureMapping() []
0x00000000DFFBE9CB UnrealLightmass.exe!Lightmass::FStaticLightingSystem::ThreadLoop() []
0x00000000DFFB2D29 UnrealLightmass.exe!Lightmass::FMappingProcessingThreadRunnable::Run() []
0x0000000020AE6F0C UnrealLightmass-Core.dll!UnknownFunction []
0x0000000020AD7AD3 UnrealLightmass-Core.dll!UnknownFunction []
0x00000000864B1FE4 KERNEL32.DLL!UnknownFunction []
0x00000000881AEF91 ntdll.dll!UnknownFunction []
0x00000000881AEF91 ntdll.dll!UnknownFunction []

I only changed some Meshes with Mesh Tool from the Marketplace and now I can’t build lighting anymore in my whole level.
I can build light in a different Project though


I can build each sublevel individually, but I cannot build the Light when I have the Persistent Level…

Hi Raildex_,

Are you able to reproduce this issue in a clean project without any 3rd party content? If you get that same issue to occur with the default engine meshes (such as the cube or the sphere) and can provide some repro steps, that would be helpful. Otherwise, it may be a problem with the mesh tool you got from the marketplace.

I couldn’t reproduce it, but my guess is that Lightmass doesn’t like bad (Lightmap) UVs.
For example a whole cube textured with “Wall Planar” means that Top and Bottom have bad UVs.
Giving every face proper UVs somehow solved the problem.

Hi Raildex,

I’m glad you were able to solve the problem by fixing the UVs. For tracking purposes, I am going to go ahead and mark this issue as “resolved” but if the same issue happens again, then please respond to this message with additional information and we will investigate as soon as possible.