error building lighting

Development Rendering
1

im trying to buld lighting on a large map and
i get this error

Error <None> === Lightmass crashed: ===
Assertion failed: Importer.ImportData((FBaseMaterialData*)this) [File:D:\BuildFarm\buildmachine_++depot+UE4-Releases+4.5\Engine\Source\Programs\UnrealLightmass\Private\ImportExport\Material.cpp] [Line: 14]

KERNELBASE.dll!UnknownFunction (0x00007ffdba30606c) + 0 bytes [UnknownFile:0]
UnrealLightmass-Core.dll!UnknownFunction (0x00007ffd81c1c9e4) + 0 bytes [UnknownFile:0]
UnrealLightmass-Core.dll!UnknownFunction (0x00007ffd81b013c8) + 0 bytes [UnknownFile:0]
UnrealLightmass-Core.dll!UnknownFunction (0x00007ffd81ae753a) + 0 bytes [UnknownFile:0]
UnrealLightmass.exe!UnknownFunction (0x00007ff64e437eac) + 0 bytes [UnknownFile:0]
UnrealLightmass.exe!UnknownFunction (0x00007ff64e3d8b40) + 0 bytes [UnknownFile:0]
UnrealLightmass.exe!UnknownFunction (0x00007ff64e439f8d) + 0 bytes [UnknownFile:0]
UnrealLightmass.exe!UnknownFunction (0x00007ff64e437b85) + 0 bytes [UnknownFile:0]
UnrealLightmass.exe!UnknownFunction (0x00007ff64e3dec71) + 0 bytes [UnknownFile:0]
UnrealLightmass.exe!UnknownFunction (0x00007ff64e43918f) + 0 bytes [UnknownFile:0]
UnrealLightmass.exe!UnknownFunction (0x00007ff64e43a4ef) + 0 bytes [UnknownFile:0]
UnrealLightmass.exe!UnknownFunction (0x00007ff64e40cc05) + 0 bytes [UnknownFile:0]
UnrealLightmass.exe!UnknownFunction (0x00007ff64e440a92) + 0 bytes [UnknownFile:0]
UnrealLightmass.exe!UnknownFunction (0x00007ff64e45bf60) + 0 bytes [UnknownFile:0]
UnrealLightmass.exe!UnknownFunction (0x00007ff64e4ad827) + 0 bytes [UnknownFile:0]
KERNEL32.DLL!UnknownFunction (0x00007ffdbcc516ad) + 0 bytes [UnknownFile:0]
ntdll.dll!UnknownFunction (0x00007ffdbcf14409) + 0 bytes [UnknownFile:0]
ntdll.dll!UnknownFunction (0x00007ffdbcf14409) + 0 bytes [UnknownFile:0]

when the map was unedited (flat plane) it built just fine.
know i have 20gb of ram 2x xeon 5650 @ 2.67ghz(24 threads)
and amd 7970
so that shouldn’t be the issue.
thanks.

2

It’s possible that it ran out of memory, on large maps it’s very possible to use up your memory even with 20GB. Lots of foliage and large landscapes can use up a lot of memory. That’s why on games that have really large maps like Battlefield or GTA they don’t use lightmaps because even if they render it it would take a massive amount of storage.

3

So you just don’t build lighting if its a very large map?

4

There’s also level streaming, so if you want a very large map you can split it up into different levels where you would only have to build lighting for just that part, then stream it in to the larger map. But again, most games avoid using so much memory by using fully dynamic lighting systems.