Description

A crash occurs when trying to use the Mesh Reduction tool for the ScotsPine_01 static mesh from the Open World Demo collection.

The assets from this project are usually very processor heavy due to the high resolution textures and number of triangles. Working with large numbers of these can affect performance so it would make sense to have more accurate and controlled LODs.

I think the user was originally attempting this with the asset as the transition from LOD2 to LOD3 was a mesh to billboard transition. The ultimate goal was to have a lower poly LOD3 without it being a billboard.

Steps to Reproduce

1. Open attached project (see comments for shareable link)
2. Open the ScotsPine_01 static mesh and set the Number of LODs to 3.0
3. Apply Changes.
4. Set the Number of LODs back to 4.0
5. Under LOD3 set the Percent Triangles in the Reduction Settings to 50.0
6. Apply Changes.

Outcome Crash occurs after applying changes and attempting to create a new LOD using the Percent Triangles.

Expected No crash and LOD3 now has have the number of Triangles as LOD2 which is where LOD3 was copied.

Callstack

UE4Editor_QuadricMeshReduction!TQuadricAttr<29>::Evaluate() quadric.h:616
UE4Editor_QuadricMeshReduction!TMeshSimplifier<TVertSimp<8>,29>::ComputeNewVerts() meshsimplify.h:892
UE4Editor_QuadricMeshReduction!TMeshSimplifier<TVertSimp<8>,29>::ComputeEdgeCollapseCost() meshsimplify.h:910
UE4Editor_QuadricMeshReduction!TMeshSimplifier<TVertSimp<8>,29>::InitCosts() meshsimplify.h:398
UE4Editor_QuadricMeshReduction!FQuadricSimplifierMeshReduction::Reduce() quadricmeshreduction.cpp:339
UE4Editor_MeshUtilities!FStaticMeshUtilityBuilder::ReduceLODs() meshutilities.cpp:3737
UE4Editor_MeshUtilities!FMeshUtilities::BuildStaticMesh() meshutilities.cpp:4031
UE4Editor_Engine!FStaticMeshRenderData::Cache() staticmesh.cpp:1367
UE4Editor_Engine!UStaticMesh::CacheDerivedData() staticmesh.cpp:2221
UE4Editor_Engine!UStaticMesh::Build() staticmeshbuild.cpp:97
UE4Editor_Engine!UStaticMesh::PostEditChangeProperty() staticmesh.cpp:1864
UE4Editor_CoreUObject!UObject::PostEditChange() obj.cpp:285
UE4Editor_StaticMeshEditor!FLevelOfDetailSettingsLayout::ApplyChanges() staticmesheditortools.cpp:2698
UE4Editor_StaticMeshEditor!FMeshReductionSettingsLayout::OnApplyChanges() staticmesheditortools.cpp:1181
UE4Editor_StaticMeshEditor!TMemberFunctionCaller<FMeshReductionSettingsLayout,FReply() delegateinstanceinterface.h:161
UE4Editor_StaticMeshEditor!TTupleImpl<TIntegerSequence<unsigned int> >::ApplyAfter<TMemberFunctionCaller<FMeshReductionSettingsLayout,FReply() tuple.h:116
UE4Editor_StaticMeshEditor!TBaseSPMethodDelegateInstance<0,FMeshReductionSettingsLayout,0,FReply __cdecl() delegateinstancesimpl.h:318
UE4Editor_Slate!TBaseDelegate<FReply>::Execute() delegatesignatureimpl.inl:522
UE4Editor_Slate!SButton::OnMouseButtonUp() sbutton.cpp:275
UE4Editor_Slate!<lambda_8d0e9a1da76abd0a756a3a9d775f5ed1>::operator() slateapplication.cpp:5010
UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_8d0e9a1da76abd0a756a3a9d775f5ed1> >() slateapplication.cpp:215
UE4Editor_Slate!FSlateApplication::RoutePointerUpEvent() slateapplication.cpp:4999
UE4Editor_Slate!FSlateApplication::ProcessMouseButtonUpEvent() slateapplication.cpp:5462
UE4Editor_Slate!FSlateApplication::OnMouseUp() slateapplication.cpp:5439
UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() windowsapplication.cpp:1652
UE4Editor_Core!FWindowsApplication::DeferMessage() windowsapplication.cpp:2071
UE4Editor_Core!FWindowsApplication::ProcessMessage() windowsapplication.cpp:814
UE4Editor_Core!FWindowsApplication::AppWndProc() windowsapplication.cpp:678
user32!<Unknown>
user32!<Unknown>
UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() windowsplatformmisc.cpp:951
UE4Editor!FEngineLoop::Tick() launchengineloop.cpp:2811
UE4Editor!GuardedMain() launch.cpp:152
UE4Editor!GuardedMainWrapper() launchwindows.cpp:126
UE4Editor!WinMain() launchwindows.cpp:202
UE4Editor!__scrt_common_main_seh() exe_common.inl:264
kernel32!<Unknown>
ntdll!<Unknown>

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Unresolved
ComponentRendering
Affects Versions4.14.34.15
Target Fix4.24
CreatedJan 30, 2017
UpdatedJul 11, 2019