Fix for crash changing MaterialQualityLevel

Development Rendering
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1

This question was created in reference to: [Render code crashes caused by ShaderMap mismatch in [Content removed]

We are experiencing this same issue as the other developer, however we have found a fix. The issue is because in ScalabilityCVarsSinkCallback(), when it creates the FGlobalComponentRecreateRenderStateContext, the constructor of it calls UpdateAllPrimitiveSceneInfosForScenes(). This launches a task on RenderThread which calls FPrimitiveSceneInfo::CacheMeshDrawCommands. This can then overlap with the assignment of GCachedScalabilityCVars which causes the issue.

We were able to fix this by adding another FlushRenderingCommands() between creating the FGlobalComponentRecreateRenderStateContext and assigning GCachedScalabilityCVars here to wait for the UpdateAllPrimitiveSceneInfosForScenes RT work to finish.

We wanted to pass this along since it seemed from the other thread that Epic didn’t have a reliable repro for the issue.

Thanks!

2

Steps to Reproduce
Load into a map with many different materials using QualityLevel switch nodes and then change the MaterialQualityLevel via Scalability

3

Thanks for the fix! We’re taking a look and will likely implement something similar.

4

Hello again! Just wanted to drop this link here for tracking this issue Unreal Engine Issues and Bug Tracker (UE\-355606) which should be visible publicly soon.

5

The suggested fix does not work in raytracing path

[2026.07.29-16.17.13:988][158]LogOutputDevice: Warning: 

Script Stack (0 frames) :

[2026.07.29-16.17.13:998][158]LogWindows: Error: appError called: Assertion failed: DirtyShaderBinding.BindingType == ERayTracingLocalShaderBindingType::Transient [File:E:\Source_5.7\UnrealEngine\Engine\Source\Runtime\Renderer\Private\RayTracing\RayTracingMaterialHitShaders.cpp] [Line: 892] 


[2026.07.29-16.17.13:998][158]LogWindows: Windows GetLastError: The operation completed successfully. (0)
[2026.07.29-16.17.19:622][158]LogRHI: Error: Breadcrumbs 'RDGExecute_RenderThread'
 - RenderGraphExecute - /ViewFamilies
 - SceneRender - ViewFamilies
 - Frame 3157

[2026.07.29-16.17.19:622][158]LogWindows: Could not start crash report client using ../../../Engine/Binaries/Win64/CrashReportClient-Win64-Debug.exe
[2026.07.29-16.17.19:622][158]LogMemory: Platform Memory Stats for Windows
[2026.07.29-16.17.19:622][158]LogMemory: Process Physical Memory: 6048.88 MB used, 6090.52 MB peak
[2026.07.29-16.17.19:622][158]LogMemory: Process Virtual Memory: 14134.98 MB used, 14135.27 MB peak
[2026.07.29-16.17.19:622][158]LogMemory: Physical Memory: 19617.50 MB used,  13038.01 MB free, 32655.52 MB total
[2026.07.29-16.17.19:622][158]LogMemory: Virtual Memory: 51876.49 MB used,  16640.91 MB free, 68517.41 MB total
[2026.07.29-16.17.19:622][158]Message dialog closed, result: Ok, title: The UE-GameProject Game has crashed and will close, text: Assertion failed: DirtyShaderBinding.BindingType == ERayTracingLocalShaderBindingType::Transient [File:E:\Source_5.7\UnrealEngine\Engine\Source\Runtime\Renderer\Private\RayTracing\RayTracingMaterialHitShaders.cpp] [Line: 892] 




[2026.07.29-16.17.19:622][158]LogThreadingWindows: Error: Runnable thread Background Worker #10 crashed.
[2026.07.29-16.17.19:622][158]LogWindows: Error: === Critical error: ===
[2026.07.29-16.17.19:622][158]LogWindows: Error: 
[2026.07.29-16.17.19:622][158]LogWindows: Error: Assertion failed: DirtyShaderBinding.BindingType == ERayTracingLocalShaderBindingType::Transient [File:E:\Source_5.7\UnrealEngine\Engine\Source\Runtime\Renderer\Private\RayTracing\RayTracingMaterialHitShaders.cpp] [Line: 892] 
[2026.07.29-16.17.19:622][158]LogWindows: Error: 
[2026.07.29-16.17.19:622][158]LogWindows: Error: 
[2026.07.29-16.17.19:622][158]LogWindows: Error: 
[2026.07.29-16.17.19:622][158]LogWindows: Error: [Callstack] 0x00007ff6c834fca8 GameProject.exe!FDebug::CheckVerifyFailedImpl2() [E:\Source_5.7\UnrealEngine\Engine\Source\Runtime\Core\Private\Misc\AssertionMacros.cpp:745]
[2026.07.29-16.17.19:622][158]LogWindows: Error: [Callstack] 0x00007ff6cbe8d072 GameProject.exe!`FDeferredShadingSceneRenderer::SetupMaterialRayTracingHitGroupBindings'::`2'::<lambda_1>::operator()() [E:\Source_5.7\UnrealEngine\Engine\Source\Runtime\Renderer\Private\RayTracing\RayTracingMaterialHitShaders.cpp:892]
[2026.07.29-16.17.19:622][158]LogWindows: Error: [Callstack] 0x00007ff6cbe8bc59 GameProject.exe!`FRDGBuilder::AddSetupTask<`AddRayTracingLocalShaderBindingWriterTasks<`FDeferredShadingSceneRenderer::SetupMaterialRayTracingHitGroupBindings'::`2'::<lambda_1> >'::`4'::<lambda_1>,TArray<UE::Tasks::Private::FTaskHandle,TSizedDefaultAllocator<32> > >'::`2'::<lambda_1>::operator()() [E:\Source_5.7\UnrealEngine\Engine\Source\Runtime\RenderCore\Public\RenderGraphBuilder.inl:603]
[2026.07.29-16.17.19:622][158]LogWindows: Error: [Callstack] 0x00007ff6c7fe6b54 GameProject.exe!UE::Tasks::Private::FTaskBase::TryExecuteTask() [E:\Source_5.7\UnrealEngine\Engine\Source\Runtime\Core\Public\Tasks\TaskPrivate.h:519]
[2026.07.29-16.17.19:622][158]LogWindows: Error: [Callstack] 0x00007ff6c7fb9ee0 GameProject.exe!LowLevelTasks::TTaskDelegate<LowLevelTasks::FTask * __cdecl(bool),48>::TTaskDelegateImpl<`LowLevelTasks::FTask::Init<`UE::Tasks::Private::FTaskBase::Init'::`2'::<lambda_1> >'::`13'::<lambda_1>,0>::CallAndMove() [E:\Source_5.7\UnrealEngine\Engine\Source\Runtime\Core\Public\Async\Fundamental\TaskDelegate.h:171]
[2026.07.29-16.17.19:622][158]LogWindows: Error: [Callstack] 0x00007ff6c7fc53cc GameProject.exe!LowLevelTasks::FTask::ExecuteTask() [E:\Source_5.7\UnrealEngine\Engine\Source\Runtime\Core\Public\Async\Fundamental\Task.h:627]
[2026.07.29-16.17.19:622][158]LogWindows: Error: [Callstack] 0x00007ff6c7fc517d GameProject.exe!LowLevelTasks::FScheduler::ExecuteTask() [E:\Source_5.7\UnrealEngine\Engine\Source\Runtime\Core\Private\Async\Fundamental\Scheduler.cpp:396]
[2026.07.29-16.17.19:622][158]LogWindows: Error: [Callstack] 0x00007ff6c7fea7ee GameProject.exe!LowLevelTasks::FScheduler::WorkerLoop() [E:\Source_5.7\UnrealEngine\Engine\Source\Runtime\Core\Private\Async\Fundamental\Scheduler.cpp:757]
[2026.07.29-16.17.19:622][158]LogWindows: Error: [Callstack] 0x00007ff6c7fb2c5a GameProject.exe!`LowLevelTasks::FScheduler::CreateWorker'::`2'::<lambda_1>::operator()() [E:\Source_5.7\UnrealEngine\Engine\Source\Runtime\Core\Private\Async\Fundamental\Scheduler.cpp:220]
[2026.07.29-16.17.19:622][158]LogWindows: Error: [Callstack] 0x00007ff6c823ecf4 GameProject.exe!FThreadImpl::Run() [E:\Source_5.7\UnrealEngine\Engine\Source\Runtime\Core\Private\HAL\Thread.cpp:69]
[2026.07.29-16.17.19:622][158]LogWindows: Error: [Callstack] 0x00007ff6c8674f88 GameProject.exe!FRunnableThreadWin::Run() [E:\Source_5.7\UnrealEngine\Engine\Source\Runtime\Core\Private\Windows\WindowsRunnableThread.cpp:159]
[2026.07.29-16.17.19:622][158]LogWindows: Error: [Callstack] 0x00007ff6c866ddbf GameProject.exe!FRunnableThreadWin::GuardedRun() [E:\Source_5.7\UnrealEngine\Engine\Source\Runtime\Core\Private\Windows\WindowsRunnableThread.cpp:79]
[2026.07.29-16.17.19:622][158]LogWindows: Error: [Callstack] 0x00007ff8a6e07374 KERNEL32.DLL!UnknownFunction []
[2026.07.29-16.17.19:622][158]LogWindows: Error: 
[2026.07.29-16.17.19:622][158]LogWindows: Error: Crash in runnable thread Background Worker #10
[2026.07.29-16.17.19:629][158]LogExit: Executing StaticShutdownAfterError
[2026.07.29-16.17.19:633][158]LogWindows: FPlatformMisc::RequestExit(1, FRunnableThreadWin::GuardedRun.ExceptionHandler)
[2026.07.29-16.17.19:633][158]LogWindows: FPlatformMisc::RequestExitWithStatus(1, 3, FRunnableThreadWin::GuardedRun.ExceptionHandler)
[2026.07.29-16.17.19:633][158]LogCore: Engine exit requested (reason: Win RequestExit)
[2026.07.29-16.17.19:633][158]LogElectraPlayer: [2] IMediaPlayer::Close()
[2026.07.29-16.17.19:633][158]LogElectraPlayer: [2] Playback stopped. Last play position 18.833