Description

With ray tracing turned on, clicking on the isolate material option next to a material slot on a skeletal mesh with more than one material slot, causes the editor to crash.
 
Found in 4.22 CL# 7053647, 4.23 CL# 7208101, 4.24 CL# 7210422
 

Steps to Reproduce
  1. Open the Editor and create a third person project
  2. Enable ray tracing and restart the Editor
  3. Open the Mannequin mesh and isolate one of the material elements

Results:
Crash

Expected:
Material element would be isolated correctly

Callstack
Assertion failed: Instance.Materials.Num() == Instance.Geometry->Initializer.Segments.Num() || (Instance.Geometry->Initializer.Segments.Num() == 0 && Instance.Materials.Num() == 1) [File:D:/JeremyMain/Engine/Source/Runtime/Renderer/Private/DeferredShadingRenderer.cpp] [Line: 731]

UE4Editor_Core!FWindowsErrorOutputDevice::Serialize() [d:\jeremymain\engine\source\runtime\core\private\windows\windowserroroutputdevice.cpp:79]
UE4Editor_Core!FOutputDevice::LogfImpl() [d:\jeremymain\engine\source\runtime\core\private\misc\outputdevice.cpp:71]
UE4Editor_Core!AssertFailedImplV() [d:\jeremymain\engine\source\runtime\core\private\misc\assertionmacros.cpp:101]
UE4Editor_Core!FDebug::CheckVerifyFailedImpl() [d:\jeremymain\engine\source\runtime\core\private\misc\assertionmacros.cpp:445]
UE4Editor_Renderer!FDeferredShadingSceneRenderer::GatherRayTracingWorldInstances() [d:\jeremymain\engine\source\runtime\renderer\private\deferredshadingrenderer.cpp:731]
UE4Editor_Renderer!FDeferredShadingSceneRenderer::Render() [d:\jeremymain\engine\source\runtime\renderer\private\deferredshadingrenderer.cpp:838]
UE4Editor_Renderer!RenderViewFamily_RenderThread() [d:\jeremymain\engine\source\runtime\renderer\private\scenerendering.cpp:3242]
UE4Editor_Renderer!TGraphTask<TEnqueueUniqueRenderCommandType<`FRendererModule::BeginRenderingViewFamily'::`27'::FDrawSceneCommandName,<lambda_98974a148448e2faeb6b39d7ee44228d> > >::ExecuteTask() [d:\jeremymain\engine\source\runtime\core\public\async\taskgraphinterfaces.h:847]
UE4Editor_Core!FNamedTaskThread::ProcessTasksNamedThread() [d:\jeremymain\engine\source\runtime\core\private\async\taskgraph.cpp:686]
UE4Editor_Core!FNamedTaskThread::ProcessTasksUntilQuit() [d:\jeremymain\engine\source\runtime\core\private\async\taskgraph.cpp:583]
UE4Editor_RenderCore!RenderingThreadMain() [d:\jeremymain\engine\source\runtime\rendercore\private\renderingthread.cpp:340]
UE4Editor_RenderCore!FRenderingThread::Run() [d:\jeremymain\engine\source\runtime\rendercore\private\renderingthread.cpp:471]
UE4Editor_Core!FRunnableThreadWin::Run() [d:\jeremymain\engine\source\runtime\core\private\windows\windowsrunnablethread.cpp:96]

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Fixed
ComponentRendering - Ray Tracing
Affects Versions4.224.234.24
Target Fix4.23
Fix Commit7227805
Main Commit7227806
Release Commit7227805
CreatedJul 3, 2019
ResolvedJul 8, 2019
UpdatedOct 4, 2019