Unreal Engine Issues and Bug Tracker (UE-47526)

Description

This is a common crash affecting users in 4.16.

User Descriptions

Pressing the button to restart the basic mesh in the destruction editor causes the crash.
Refreshing a Destructible Mesh that has had it's static mesh updated.
Refreshing Destructible Mesh
Imported static mesh, created destruction mesh, reimported static mesh and hit refresh on destruction mesh.

Source Context

 802       		for (int32 LodIndex = 0; LodIndex < ImportedResource->LODModels.Num(); ++LodIndex)
  803       		{
  804       			ExistingMeshDataPtr->ExistingImportMeshLodSectionMaterialData.AddZeroed();
  805       			for (int32 SectionIndex = 0; SectionIndex < ImportedResource->LODModels[LodIndex].Sections.Num(); ++SectionIndex)
  806       			{
  807       				int32 SectionMaterialIndex = ImportedResource->LODModels[LodIndex].Sections[SectionIndex].MaterialIndex;
  808       				bool SectionCastShadow = ImportedResource->LODModels[LodIndex].Sections[SectionIndex].bCastShadow;
  809       				bool SectionRecomputeTangents = ImportedResource->LODModels[LodIndex].Sections[SectionIndex].bRecomputeTangent;
  810 ***** 				ExistingMeshDataPtr->ExistingImportMeshLodSectionMaterialData[LodIndex].Add(ExistingMeshLodSectionData(ExistingMeshDataPtr->ExistingImportMaterialOriginalNameData[SectionMaterialIndex], SectionCastShadow, SectionRecomputeTangents));
  811       			}
  812       		}

Steps to Reproduce

repro steps currently unknown, but seems to occur when refreshing a destructible mesh

Callstack

Assertion failed: (Index >= 0) & (Index < ArrayNum) [File:D:\Build\++UE4+Release-4.16+Compile\Sync\Engine\Source\Runtime\Core\Public\Containers/Array.h] [Line: 633] 
Array index out of bounds: 1 from an array of size 1

UE4Editor_UnrealEd!SaveExistingSkelMeshData() [skeletalmeshimport.cpp:811]
UE4Editor_UnrealEd!SaveExistingDestMeshData() [apexdestructibleassetimport.cpp:243]
UE4Editor_UnrealEd!SetApexDestructibleAsset() [apexdestructibleassetimport.cpp:751]
UE4Editor_UnrealEd!BuildDestructibleMeshFromFractureSettings() [apexdestructibleassetimport.cpp:992]
UE4Editor_Engine!UDestructibleMesh::BuildFromStaticMesh() [destructiblemesh.cpp:717]
UE4Editor_DestructibleMeshEditor!FDestructibleMeshEditorViewportClient::RefreshFromStaticMesh() [sdestructiblemesheditorviewport.cpp:242]
UE4Editor_DestructibleMeshEditor!TBaseSPMethodDelegateInstance<0,FDestructibleMeshEditorViewportClient,0,TTypeWrapper<void> __cdecl() [delegateinstancesimpl.h:327]
UE4Editor_DestructibleMeshEditor!TBaseSPMethodDelegateInstance<0,FDestructibleMeshEditorViewportClient,0,void __cdecl() [delegateinstancesimpl.h:434]
UE4Editor_Slate!FUICommandList::ExecuteAction() [uicommandlist.cpp:97]
UE4Editor_Slate!SToolBarButtonBlock::OnClicked() [stoolbarbuttonblock.cpp:305]
UE4Editor_Slate!TMemberFunctionCaller<SToolBarButtonBlock,FReply() [delegateinstanceinterface.h:165]
UE4Editor_Slate!UE4Tuple_Private::TTupleImpl<TIntegerSequence<unsigned int> >::ApplyAfter<TMemberFunctionCaller<SToolBarButtonBlock,FReply() [tuple.h:497]
UE4Editor_Slate!TBaseSPMethodDelegateInstance<0,SToolBarButtonBlock,0,FReply __cdecl() [delegateinstancesimpl.h:327]
UE4Editor_Slate!TBaseDelegate<FReply>::Execute() [delegatesignatureimpl.inl:537]
UE4Editor_Slate!SButton::OnMouseButtonUp() [sbutton.cpp:278]
UE4Editor_Slate!<lambda_8d0e9a1da76abd0a756a3a9d775f5ed1>::operator() [slateapplication.cpp:5049]
UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_8d0e9a1da76abd0a756a3a9d775f5ed1> >() [slateapplication.cpp:239]
UE4Editor_Slate!FSlateApplication::RoutePointerUpEvent() [slateapplication.cpp:5038]
UE4Editor_Slate!FSlateApplication::ProcessMouseButtonUpEvent() [slateapplication.cpp:5515]
UE4Editor_Slate!FSlateApplication::OnMouseUp() [slateapplication.cpp:5495]
UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() [windowsapplication.cpp:1704]
UE4Editor_Core!FWindowsApplication::DeferMessage() [windowsapplication.cpp:2127]
UE4Editor_Core!FWindowsApplication::ProcessMessage() [windowsapplication.cpp:867]
UE4Editor_Core!FWindowsApplication::AppWndProc() [windowsapplication.cpp:714]
user32!UserCallWinProcCheckWow()
user32!DispatchMessageWorker()
UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() [windowsplatformmisc.cpp:1009]
UE4Editor!FEngineLoop::Tick() [launchengineloop.cpp:3058]
UE4Editor!GuardedMain() [launch.cpp:166]
UE4Editor!GuardedMainWrapper() [launchwindows.cpp:134]
UE4Editor!WinMain() [launchwindows.cpp:210]
UE4Editor!__scrt_common_main_seh() [exe_common.inl:253]
kernel32!BaseThreadInitThunk()
ntdll!RtlUserThreadStart()

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Fixed

Component	UE - Simulation - Physics - Destruction
Affects Versions	4.16
Target Fix	4.17

Fix Commit	3474099

Created	Jul 20, 2017
Resolved	Jul 20, 2017
Updated	Apr 27, 2018

UE-47526

[CrashReport] Crash related to refreshing Destructible Mesh - SaveExistingSkelMeshData()

[CrashReport] Crash related to refreshing Destructible Mesh - SaveExistingSkelMeshData()

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