Description

This issue can occur when setting the Decal Material to Instanced Static Mesh in a Raytracing enabled project. (If there is a cache, it will not crash.)
The cause is that DefaultDeferredDecalMaterial does not support Instanced Static Mesh. And there is a problem because the Default Material is used while compiling the Material.

It was confirmed that the crash can be avoided by enabling the Used with Instanced Static Mesh flag of DefaultDeferredDecalMaterial.
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Steps to Reproduce
  1. Open attached project
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  2. It crashes when I select BP_InstancedStaticMesh on the level and add an Instance
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Callstack

UE4Editor_Engine!<lambda_86491d9ce14fcdd968f3773591ec8802>::operator()() [K:\Git\UE4_26\Engine\Source\Runtime\Engine\Private\Materials\MaterialShared.cpp:2215]
UE4Editor_Engine!FMaterial::GetShader() [K:\Git\UE4_26\Engine\Source\Runtime\Engine\Private\Materials\MaterialShared.cpp:2220]
UE4Editor_Renderer!GetMaterialHitShader<TUniformLightMapPolicy<1> >() [K:\Git\UE4_26\Engine\Source\Runtime\Renderer\Private\RayTracing\RayTracingMaterialHitShaders.cpp:271]
UE4Editor_Renderer!FRayTracingMeshProcessor::Process() [K:\Git\UE4_26\Engine\Source\Runtime\Renderer\Private\RayTracing\RayTracingMaterialHitShaders.cpp:303]
UE4Editor_Renderer!FRayTracingMeshProcessor::AddMeshBatch() [K:\Git\UE4_26\Engine\Source\Runtime\Renderer\Private\RayTracing\RayTracingMaterialHitShaders.cpp:478]
UE4Editor_Renderer!FPrimitiveSceneInfo::CacheMeshDrawCommands() [K:\Git\UE4_26\Engine\Source\Runtime\Renderer\Private\PrimitiveSceneInfo.cpp:431]
UE4Editor_Renderer!FPrimitiveSceneInfo::AddStaticMeshes() [K:\Git\UE4_26\Engine\Source\Runtime\Renderer\Private\PrimitiveSceneInfo.cpp:550]
UE4Editor_Renderer!FPrimitiveSceneInfo::AddToScene() [K:\Git\UE4_26\Engine\Source\Runtime\Renderer\Private\PrimitiveSceneInfo.cpp:712]
UE4Editor_Renderer!FScene::UpdateAllPrimitiveSceneInfos() [K:\Git\UE4_26\Engine\Source\Runtime\Renderer\Private\RendererScene.cpp:4041]
UE4Editor_Engine!TEnqueueUniqueRenderCommandType<`UpdateAllPrimitiveSceneInfosForSingleComponent'::`8'::UpdateAllPrimitiveSceneInfosCmdName,<lambda_7c2619a60bc4a8837b3167b4a4240301> >::DoTask() [K:\Git\UE4_26\Engine\Source\Runtime\RenderCore\Public\RenderingThread.h:183]
UE4Editor_Engine!TGraphTask<TEnqueueUniqueRenderCommandType<`UpdateAllPrimitiveSceneInfosForSingleComponent'::`8'::UpdateAllPrimitiveSceneInfosCmdName,<lambda_7c2619a60bc4a8837b3167b4a4240301> > >::ExecuteTask() [K:\Git\UE4_26\Engine\Source\Runtime\Core\Public\Async\TaskGraphInterfaces.h:886]
UE4Editor_Core!FNamedTaskThread::ProcessTasksNamedThread() [K:\Git\UE4_26\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:709]
UE4Editor_Core!FNamedTaskThread::ProcessTasksUntilQuit() [K:\Git\UE4_26\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:601]
UE4Editor_RenderCore!RenderingThreadMain() [K:\Git\UE4_26\Engine\Source\Runtime\RenderCore\Private\RenderingThread.cpp:373]
UE4Editor_RenderCore!FRenderingThread::Run() [K:\Git\UE4_26\Engine\Source\Runtime\RenderCore\Private\RenderingThread.cpp:509]
UE4Editor_Core!FRunnableThreadWin::Run() [K:\Git\UE4_26\Engine\Source\Runtime\Core\Private\Windows\WindowsRunnableThread.cpp:86]

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Fixed
ComponentRendering - Ray Tracing
Affects Versions4.26.1
Target Fix5.0
Fix Commit15731890
Main Commit15731890
CreatedApr 8, 2021
ResolvedJun 3, 2021
UpdatedJun 7, 2021