Description

This crash seems to only be reproducible using the TallGrass_01 asset in QAGame. Having other foliage assets selected sometimes prevents the crash, but usually any combination of assets plus TallGrass_01 will crash the editor when attempting to paint foliage onto a landscape.

This is a regression and does not happen in 4.16.3
Preparing to test in Main.

Steps to Reproduce
  1. Open QAGame
  2. Shift + 3 to enable landscape mode
  3. Set the Section Size of the new landscape to 7x7 Quads and click Create
  4. Shift + 4 to enable foliage mode
  5. In the content browser, search for TallGrass_01 static mesh
  6. Drag TallGrass_01 into the foliage type panel
  7. LMB drag across the landscape to paint the foliage

Result: Editor crashes immediately.
Expected Result: Editor paints the selected grass asset cleanly onto the landscape.

Callstack
UE4Editor-MetalRHI.dylib!FMetalDynamicRHI::RHICreateVertexBuffer() 
UE4Editor-MetalRHI.dylib!FMetalDynamicRHI::CreateVertexBuffer_RenderThread() 
UE4Editor-Engine.dylib!FStaticMeshInstanceBuffer::InitRHI() 
UE4Editor-RenderCore.dylib!FRenderResource::UpdateRHI() 
UE4Editor-Engine.dylib!FStaticMeshInstanceBuffer::UpdateRHIVertexBuffer() 
UE4Editor-Engine.dylib!FStaticMeshInstanceBuffer::UpdateRHIVertexBuffer() 
UE4Editor-Engine.dylib!TGraphTask<FInstancedStaticMeshRenderData::UpdatePerInstanceRenderData(TSet<int, DefaultKeyFuncs<int, false>, FDefaultSetAllocator> const&)::EURCMacro_FPerInstanceRenderDataBufferUpdate>::ExecuteTask()
UE4Editor-Core.dylib!FNamedTaskThread::ProcessTasksNamedThread() 
UE4Editor-Core.dylib!FNamedTaskThread::ProcessTasksUntilQuit() 
UE4Editor-Core.dylib!FTaskGraphImplementation::ProcessThreadUntilRequestReturn() 
UE4Editor-RenderCore.dylib!RenderingThreadMain() 
UE4Editor-RenderCore.dylib!FRenderingThread::Run() 
UE4Editor-Core.dylib!FRunnableThreadPThread::Run() 
UE4Editor-Core.dylib!FRunnableThreadPThread::_ThreadProc() 
libsystem_pthread.dylib!<Unknown> 
libsystem_pthread.dylib!<Unknown> 
libsystem_pthread.dylib!<Unknown> 

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Fixed
ComponentTools - Landscape
Affects Versions4.17
Target Fix4.17.2
Fix Commit3593597
Main Commit3621569
CreatedAug 3, 2017
ResolvedAug 17, 2017
UpdatedApr 27, 2018