Unreal crash when i try to build lights

=== Lightmass crashed: ===
Assertion failed: rtcDeviceGetError(EmbreeDevice) == RTC_NO_ERROR [File:D:\build++UE5\Sync\Engine\Source\Programs\UnrealLightmass\Private\Lighting\Embree.cpp] [Line: 721]

0x00007ff70cb30cb3 UnrealLightmass.exe!Lightmass::FEmbreeAggregateMesh::PrepareForRaytracing() []
0x00007ff70cb550c0 UnrealLightmass.exe!Lightmass::FStaticLightingSystem::FStaticLightingSystem() []
0x00007ff70cb098b1 UnrealLightmass.exe!Lightmass::BuildStaticLighting() []
0x00007ff70cb2cda1 UnrealLightmass.exe!Lightmass::LightmassMain() []
0x00007ff70cb4cf97 UnrealLightmass.exe!main() []
0x00007ff70cbb5ebc UnrealLightmass.exe!__scrt_common_main_seh() []
0x00007ffd37807034 KERNEL32.DLL!UnknownFunction []
0x00007ffd397626a1 ntdll.dll!UnknownFunction []


Hi, Have you solved this? I’m having the same problem

1 Like

Hi. If you put the grass on the movable, the problem will disappear.

The error message you provided is indicating that there is an assertion failure in the Embree.cpp file of the UnrealLightmass.exe program. This error is related to the Embree library, which is used by Unreal Engine’s Lightmass system to perform ray tracing calculations.

The error message states that the Embree device returned an error, specifically RTC_NO_ERROR, indicating that there is some issue with the Embree library that is preventing it from functioning properly. This error can be caused by a variety of factors such as outdated graphics drivers, a problem with the Embree library installation or conflict with other software running on your computer.

Some solutions that you can try to resolve this issue include:

  • Updating your graphics drivers to the latest version.
  • Make sure your system meets the minimum requirements of Unreal Engine 5.
  • Reinstall Unreal Engine 5 to ensure that all necessary files are in place.

If you continue to experience this issue and none of the solutions work, you may want to consider submitting a bug report to the Unreal Engine team through their official website, as this will help them to investigate and resolve the issue. It’s also important to include the error message and steps you have taken to troubleshoot the problem.