Description

Building HLODs causes a crash. This only seems to occur in some levels as shown in the attached project.

Found in 4.22 CL# 7053642, 4.23 CL# 7948402, 4.24 CL# 8124506

Steps to Reproduce
  1. Open attached project
  2. Load the level "KooijmanNew"
  3. Open the HLOD outliner
  4. Build HLODs

Result:
The Editor crashes

Expected:
HLODs would be built

Note:
This doesn't occur in the the "Test" level in the project provided following the same steps

Callstack
Fatal error!

Unhandled Exception: EXCEPTION_INT_DIVIDE_BY_ZERO

0x00007ffea69613ed UE4Editor-MeshMergeUtilities.dll!FMeshMergeUtilities::MergeFlattenedMaterials() [d:\build\++ue4\sync\engine\source\developer\meshmergeutilities\private\meshmergeutilities.cpp:862]
0x00007ffea695e0dd UE4Editor-MeshMergeUtilities.dll!FMeshMergeUtilities::MergeComponentsToStaticMesh() [d:\build\++ue4\sync\engine\source\developer\meshmergeutilities\private\meshmergeutilities.cpp:2263]
0x00007fff067958b8 UE4Editor-HierarchicalLODUtilities.dll!FHierarchicalLODUtilities::BuildStaticMeshForLODActor() [d:\build\++ue4\sync\engine\source\developer\hierarchicallodutilities\private\hierarchicallodutilities.cpp:315]
0x00007fff06796283 UE4Editor-HierarchicalLODUtilities.dll!FHierarchicalLODUtilities::BuildStaticMeshForLODActor() [d:\build\++ue4\sync\engine\source\developer\hierarchicallodutilities\private\hierarchicallodutilities.cpp:233]
0x00007ffeb622477d UE4Editor-UnrealEd.dll!FHierarchicalLODBuilder::BuildMeshesForLODActors() [d:\build\++ue4\sync\engine\source\editor\unrealed\private\hierarchicallod.cpp:712]
0x00007ffe9ad12592 UE4Editor-HierarchicalLODOutliner.dll!HLODOutliner::SHLODOutliner::HandleForceBuildLODActors() [d:\build\++ue4\sync\engine\source\editor\hierarchicallodoutliner\private\hlodoutliner.cpp:846]
0x00007ffe9ad047b4 UE4Editor-HierarchicalLODOutliner.dll!TBaseSPMethodDelegateInstance<0,HLODOutliner::SHLODOutliner,0,FReply __cdecl(void)>::Execute() [d:\build\++ue4\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:279]
0x00007ffeb7352a12 UE4Editor-Slate.dll!SButton::OnMouseButtonUp() [d:\build\++ue4\sync\engine\source\runtime\slate\private\widgets\input\sbutton.cpp:293]
0x00007ffeb71a4021 UE4Editor-Slate.dll!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_6c1f6b862bcfb82ea6dcab28fbcc9463> >() [d:\build\++ue4\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:271]
0x00007ffeb7220301 UE4Editor-Slate.dll!FSlateApplication::RoutePointerUpEvent() [d:\build\++ue4\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5598]
0x00007ffeb720aaca UE4Editor-Slate.dll!FSlateApplication::ProcessMouseButtonUpEvent() [d:\build\++ue4\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:6203]
0x00007ffeb7200414 UE4Editor-Slate.dll!FSlateApplication::OnMouseUp() [d:\build\++ue4\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:6176]
0x00007fff0e10b8e0 UE4Editor-ApplicationCore.dll!FWindowsApplication::ProcessDeferredMessage() [d:\build\++ue4\sync\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:1842]
0x00007fff0e0fef9f UE4Editor-ApplicationCore.dll!FWindowsApplication::DeferMessage() [d:\build\++ue4\sync\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:2292]
0x00007fff0e10d77f UE4Editor-ApplicationCore.dll!FWindowsApplication::ProcessMessage() [d:\build\++ue4\sync\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:1522]
0x00007fff0e0fc090 UE4Editor-ApplicationCore.dll!FWindowsApplication::AppWndProc() [d:\build\++ue4\sync\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:772]
0x00007fff25c7ca66 USER32.dll!UnknownFunction []
0x00007fff25c7c582 USER32.dll!UnknownFunction []
0x00007fff0e10e946 UE4Editor-ApplicationCore.dll!FWindowsPlatformApplicationMisc::PumpMessages() [d:\build\++ue4\sync\engine\source\runtime\applicationcore\private\windows\windowsplatformapplicationmisc.cpp:130]
0x00007ff76d755d3e UE4Editor.exe!FEngineLoop::Tick() [d:\build\++ue4\sync\engine\source\runtime\launch\private\launchengineloop.cpp:3882]
0x00007ff76d76554c UE4Editor.exe!GuardedMain() [d:\build\++ue4\sync\engine\source\runtime\launch\private\launch.cpp:168]
0x00007ff76d7655ca UE4Editor.exe!GuardedMainWrapper() [d:\build\++ue4\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:145]
0x00007ff76d77316c UE4Editor.exe!WinMain() [d:\build\++ue4\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:275]
0x00007ff76d775b8e UE4Editor.exe!__scrt_common_main_seh() [d:\agent\_work\3\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288]
0x00007fff258c7974 KERNEL32.DLL!UnknownFunction []
0x00007fff2863a271 ntdll.dll!UnknownFunction []

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Fixed
ComponentTools - HLOD
Affects Versions4.224.234.24
Target Fix4.23
Fix Commit8219953
Main Commit8223716
Release Commit8219953
CreatedAug 21, 2019
ResolvedAug 23, 2019
UpdatedSep 12, 2019