Unreal Engine Issues and Bug Tracker (UE-40229)

Description

This is a regression in behavior between 4.14.1 and 4.14.2!

The editor will crash when importing FBX meshes that have multiple material ID assignments. If it's a single material ID it will import without the crash.

Tested with:
Working: 4.14.1 Binary CL-3224400
Broken: 4.14.2 Binary CL-3241561
Working: 4.15 Dev-Main CL-3238204
Working: 4.16 Dev-Main CL-3247095
Working: 4.15 Automated Binary Build CL-3247232

Added test assets from 3Ds Max 2016 that recreate the crash attached below.

MultiMatBox uses 3 material elements assigned to a box that is 100x100x100cm. - Causes Crash
Box2 uses a single material element on a box that is 100x100x100cm, - Does not cause crash.

Steps to Reproduce

1. Import attached asset
2. Use default settings for the Import Options

Results: The editor will crash

Assertion failed: (Index >= 0) & (Index < ArrayNum) [Link Removed] [Line: 634]
Array index out of bounds: -1 from an array of size

Callstack

MachineId:7D8A1A304BE9658328C158A3D14CC774
EpicAccountId:7c6293d6bf1940c0bc89e1494c5ba9d7

Assertion failed: (Index >= 0) & (Index < ArrayNum) [Link Removed] [Line: 634]
Array index out of bounds: -1 from an array of size 1

UE4Editor_Core!FDebug::AssertFailed() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\core\private\misc\assertionmacros.cpp:332]
UE4Editor_UnrealEd!UnFbx::FFbxImporter::ReorderMaterialToFbxOrder() [d:\build\++ue4+release-4.14+compile\sync\engine\source\editor\unrealed\private\fbx\fbxstaticmeshimport.cpp:1619]
UE4Editor_UnrealEd!UFbxFactory::FactoryCreateBinary() [d:\build\++ue4+release-4.14+compile\sync\engine\source\editor\unrealed\private\fbx\fbxfactory.cpp:297]
UE4Editor_UnrealEd!UFactory::FactoryCreateFile() [d:\build\++ue4+release-4.14+compile\sync\engine\source\editor\unrealed\private\factories\factory.cpp:75]
UE4Editor_UnrealEd!UFactory::ImportObject() [d:\build\++ue4+release-4.14+compile\sync\engine\source\editor\unrealed\private\factories\factory.cpp:150]
UE4Editor_AssetTools!FAssetTools::ImportAssetsInternal() [d:\build\++ue4+release-4.14+compile\sync\engine\source\developer\assettools\private\assettools.cpp:1375]
UE4Editor_AssetTools!FAssetTools::ImportAssets() [d:\build\++ue4+release-4.14+compile\sync\engine\source\developer\assettools\private\assettools.cpp:628]
UE4Editor_AssetTools!FAssetTools::ImportAssets() [d:\build\++ue4+release-4.14+compile\sync\engine\source\developer\assettools\private\assettools.cpp:561]
UE4Editor_ContentBrowser!SContentBrowser::ImportAsset() [d:\build\++ue4+release-4.14+compile\sync\engine\source\editor\contentbrowser\private\scontentbrowser.cpp:790]
UE4Editor_ContentBrowser!SContentBrowser::HandleImportClicked() [d:\build\++ue4+release-4.14+compile\sync\engine\source\editor\contentbrowser\private\scontentbrowser.cpp:781]
UE4Editor_ContentBrowser!TMemberFunctionCaller<SContentBrowser,FReply (__cdecl SContentBrowser::*)(void) __ptr64>::operator()<>() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\core\public\delegates\delegateinstanceinterface.h:161]
UE4Editor_ContentBrowser!TTupleImpl<TIntegerSequence<unsigned int> >::ApplyAfter<TMemberFunctionCaller<SContentBrowser,FReply (__cdecl SContentBrowser::*)(void) __ptr64> >() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\core\public\delegates\tuple.h:116]
UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<0,SContentBrowser,0,FReply __cdecl(void)>::Execute() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:318]
UE4Editor_Slate!TBaseDelegate<FReply>::Execute() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:522]
UE4Editor_Slate!SButton::OnMouseButtonUp() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\slate\private\widgets\input\sbutton.cpp:275]
UE4Editor_Slate!<lambda_8d0e9a1da76abd0a756a3a9d775f5ed1>::operator()() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5010]
UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_8d0e9a1da76abd0a756a3a9d775f5ed1> >() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:215]
UE4Editor_Slate!FSlateApplication::RoutePointerUpEvent() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:4999]
UE4Editor_Slate!FSlateApplication::ProcessMouseButtonUpEvent() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5462]
UE4Editor_Slate!FSlateApplication::OnMouseUp() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5439]
UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\core\private\windows\windowsapplication.cpp:1652]
UE4Editor_Core!FWindowsApplication::DeferMessage() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\core\private\windows\windowsapplication.cpp:2071]
UE4Editor_Core!FWindowsApplication::ProcessMessage() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\core\private\windows\windowsapplication.cpp:814]
UE4Editor_Core!FWindowsApplication::AppWndProc() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\core\private\windows\windowsapplication.cpp:678]
user32
user32
UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\core\private\windows\windowsplatformmisc.cpp:951]
UE4Editor!FEngineLoop::Tick() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\launch\private\launchengineloop.cpp:2811]
UE4Editor!GuardedMain() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\launch\private\launch.cpp:152]
UE4Editor!GuardedMainWrapper() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:126]
UE4Editor!WinMain() [d:\build\++ue4+release-4.14+compile\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:202]
UE4Editor!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:264]
kernel32
ntdll

Community References

Multiple issues with UE 5.1 under macOS, help.

Ue4 crashing when importing skeletal mesh

Importing an FBX from blender with different materials crashes the editor.

Engine crash on importing fbx in 4.14.2

Unreal Engine crashes when importing .obj file

FBX Crash 4.14.2 with multiple material IDs

Unreal Engine crashes when importing .obj file

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Fixed

Component	UE - Editor - Content Pipeline - Import and Export
Affects Versions	4.14.2
Target Fix	4.14.3

Fix Commit	3247844

Created	Jan 5, 2017
Resolved	Jan 5, 2017
Updated	Apr 27, 2018

UE-40229

Editor Crashes when importing some FBXs with multiple Material IDs in 4.14.2

Editor Crashes when importing some FBXs with multiple Material IDs in 4.14.2

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