Lightmass is crashing when using a material that has "Cast Shadow as Masked" set to true in its properties.

Found in 4.18 P3 CL#3676890

Unable to reproduce in 4.16.3 CL# 3561208 and 4.17.2 CL#3658906, this is a regression.

Steps to Reproduce
  1. Create a blank project
  2. Create a new material
  3. Apply new material to floor mesh
  4. build lighting
  5. open new material
  6. in the material properties, under Lightmass Settings, check "Cast Shadow as Masked"
  7. save the material
  8. build lighting

result: lightmass crashes
expected: lighting built successfully

<None> === Lightmass crashed: ===Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x00000002
Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x00000002

0x000000001E8FD340 UnrealLightmass-Core.dll!UnknownFunction []
0x0000000047014E6C UnrealLightmass.exe!UnknownFunction []
0x0000000047013BA8 UnrealLightmass.exe!UnknownFunction []
0x000000001F4F6FAC embree.dll!UnknownFunction []
0x000000001EF38AD0 embree.dll!UnknownFunction []
0x00000000470294E4 UnrealLightmass.exe!UnknownFunction []
0x000000004707BEBF UnrealLightmass.exe!UnknownFunction []
0x000000004707B892 UnrealLightmass.exe!UnknownFunction []
0x000000004709D158 UnrealLightmass.exe!UnknownFunction []
0x000000001EB86AEC UnrealLightmass-Core.dll!UnknownFunction []
0x000000001EB776B3 UnrealLightmass-Core.dll!UnknownFunction []
0x00000000314413D2 KERNEL32.DLL!UnknownFunction []
0x00000000335D54E4 ntdll.dll!UnknownFunction []
0x00000000335D54E4 ntdll.dll!UnknownFunction []

Community References

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ComponentUE - Rendering
Affects Versions4.18
Target Fix4.18
Fix Commit3681973
Release Commit3681973
CreatedOct 4, 2017
ResolvedOct 5, 2017
UpdatedApr 27, 2018