Repro Rate 15/25

Regression set to Yes as this was not found on //UE5/Release-5.2 CL 26001984 Binary

Building Nanite with a Landscape that has a material including Landscape Visibility Mask still gives an Assert after building. The initial build does work but you still get the assert if doing the steps over again. It is inconsistent, but it still happens.

Steps to Reproduce
  1. Open a Blank Project
  2. File > New Level > Basic Level
  3. Open Landscape Tool (Shift + 2)
  4. Create a landscape with the default settings
  5. Save your level with default name
  6. Once build head to Tools > Convert Level > Select the saved level and select Open
  7. Once loaded in, Windows > World Partition > World Partition Editor
  8. Within the World Partition Editor, highlight the landscape, right-click > Load Region From Selection
  9. In the Content Browser, Add > Material with default name
  10. Double click to open the Material
  11. Within the Material Graph, right click and add Constant3Vector
  12. Connect it with Base Color
  13. Select the node, and within the Details panel change the Constant to whatever color
  14. Right click within the Material Graph and add LandscapeVisibilityMask
    1. Connect this to Opacity Mask
  15. Select Apply and Save
  16. Back within the Level Editor, in the World Outliner, select the Landscape
  17. Within the Details Panel, under Landscape > Landscape Material, add the newly created Material
  18. In the Detail Panel, under Nanite, enable Nanite
  19. Enter Landscape Mode (Shift + 2)
  20. Using the Sculpt and Visibility Tool, edit the landscape
  21. Within the Details Panel, under Nanite, select the Build Nanite button
  22. Once built, edit the landscape once more
  23. Within the Details Panel, under Nanite, select Build Nanite once more
  24. May need to repeat steps 22 and 23

Expected Results: Each time, the Nanite build is successful

Actual Results: The engine crashes and the assert appears

UnrealEditor-Landscape!ALandscapeProxy::ExportToRawMeshDataCopyNew(ALandscapeProxy::FRawMeshExportParams const &,FMeshDescription &,UE::Landscape::Nanite::FAsyncBuildData const &) [LandscapeEdit.cpp:4187]
UnrealEditor-Landscape!ALandscapeProxy::ExportToRawMeshDataCopy(ALandscapeProxy::FRawMeshExportParams const &,FMeshDescription &,UE::Landscape::Nanite::FAsyncBuildData const &) [LandscapeEdit.cpp:3853]
UnrealEditor-Landscape!static void `ULandscapeNaniteComponent::InitializeForLandscapeAsync'::`2'::<lambda_1>::operator() [LandscapeNaniteComponent.cpp:209]
UnrealEditor-Landscape!TGraphTask<TFunctionGraphTaskImpl<void ,0> >::ExecuteTask(TArray<FBaseGraphTask *,TSizedDefaultAllocator<32> > &,ENamedThreads::Type,bool) [TaskGraphInterfaces.h:1265]
UnrealEditor-Core!`LowLevelTasks::FTask::Init<`FTaskGraphCompatibilityImplementation::QueueTask(FBaseGraphTask *,bool,ENamedThreads::Type,ENamedThreads::Type) [Task.h:499]
UnrealEditor-Core!class LowLevelTasks::FTask * LowLevelTasks::TTaskDelegate<LowLevelTasks::FTask * __cdecl(bool) [TaskDelegate.h:171]
UnrealEditor-Core!LowLevelTasks::FTask::ExecuteTask() [Task.h:627]
UnrealEditor-Core!LowLevelTasks::FScheduler::ExecuteTask(LowLevelTasks::FTask * &) [Scheduler.cpp:172]
UnrealEditor-Core!LowLevelTasks::FScheduler::TryExecuteTaskFrom<LowLevelTasks::TLocalQueueRegistry<1024>::TLocalQueue,&LowLevelTasks::TLocalQueueRegistry<1024>::TLocalQueue::DequeueGlobal(bool,bool) [Scheduler.cpp:350]
UnrealEditor-Core!LowLevelTasks::FScheduler::WorkerMain(LowLevelTasks::FSleepEvent *,LowLevelTasks::TLocalQueueRegistry<1024>::TLocalQueue *,unsigned int,bool) [Scheduler.cpp:378]
UnrealEditor-Core!static void UE::Core::Private::Function::TFunctionRefCaller<`LowLevelTasks::FScheduler::CreateWorker'::`2'::<lambda_1>,void __cdecl(void) [Function.h:480]
UnrealEditor-Core!FThreadImpl::Run() [Thread.cpp:69]
UnrealEditor-Core!FRunnableThreadWin::Run() [WindowsRunnableThread.cpp:149]
UnrealEditor-Core!FRunnableThreadWin::GuardedRun() [WindowsRunnableThread.cpp:79]
KERNEL32!7ffa00630000  + 17614
ntdll!7ffa018d0000  + 526b1 

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ComponentUE - LD & Modeling - Terrain - Landscape
Affects Versions5.3
Target Fix5.4
Fix Commit29023629
Main Commit29025960
CreatedAug 28, 2023
ResolvedOct 23, 2023
UpdatedNov 21, 2023
View Jira Issue