Unreal Engine Issues and Bug Tracker (UE-194086)

Description

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

Open a Blank Project
File > New Level > Basic Level
Open Landscape Tool (Shift + 2)
Create a landscape with the default settings
Save your level with default name
Once build head to Tools > Convert Level > Select the saved level and select Open
Once loaded in, Windows > World Partition > World Partition Editor
Within the World Partition Editor, highlight the landscape, right-click > Load Region From Selection
In the Content Browser, Add > Material with default name
Double click to open the Material
Within the Material Graph, right click and add Constant3Vector
Connect it with Base Color
Select the node, and within the Details panel change the Constant to whatever color
Right click within the Material Graph and add LandscapeVisibilityMask
1. Connect this to Opacity Mask
Select Apply and Save
Back within the Level Editor, in the World Outliner, select the Landscape
Within the Details Panel, under Landscape > Landscape Material, add the newly created Material
In the Detail Panel, under Nanite, enable Nanite
Enter Landscape Mode (Shift + 2)
Using the Sculpt and Visibility Tool, edit the landscape
Within the Details Panel, under Nanite, select the Build Nanite button
Once built, edit the landscape once more
Within the Details Panel, under Nanite, select Build Nanite once more
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

Callstack

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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Fixed

Component	UE - LD & Modeling - Terrain - Landscape
Affects Versions	5.3
Target Fix	5.4

Fix Commit	29023629
Main Commit	29025960

Created	Aug 28, 2023
Resolved	Oct 23, 2023
Updated	Nov 21, 2023

UE-194086

Building Nanite on a Landscape with Visibility Mask multiple times gives an Assert

Building Nanite on a Landscape with Visibility Mask multiple times gives an Assert

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