Lightweight Niagara causes 5.7 to Crash!

Development Getting Started & Setup
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1

Whenever I try to open a niagara system that uses a Lightweight emitter, or anything that references a Niagara System that uses a Lightweight emitter in UE 5.7.1, it causes the engine to crash. Here’s the crash log:

Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x0000000000000480

UnrealEditor_NiagaraEditor
UnrealEditor_NiagaraEditor
UnrealEditor_Niagara
UnrealEditor_Niagara
UnrealEditor_Niagara
UnrealEditor_Niagara
UnrealEditor_Niagara
UnrealEditor_Niagara
UnrealEditor_Niagara
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Niagara
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_Engine
UnrealEditor_UnrealEd
UnrealEditor_UnrealEd
UnrealEditor_UnrealEd
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_CoreUObject
UnrealEditor_ContentBrowserAssetDataSource
UnrealEditor_ContentBrowserAssetDataSource
UnrealEditor_ContentBrowserAssetDataSource
UnrealEditor_ContentBrowserAssetDataSource
UnrealEditor_ContentBrowser
UnrealEditor_ContentBrowser
UnrealEditor_ContentBrowser
UnrealEditor_ContentBrowser
UnrealEditor_ContentBrowser
UnrealEditor_ContentBrowser
UnrealEditor_ContentBrowser
UnrealEditor_Slate
UnrealEditor_Slate
UnrealEditor_Slate
UnrealEditor_Slate
UnrealEditor_ApplicationCore
UnrealEditor_ApplicationCore
UnrealEditor_ApplicationCore
UnrealEditor_ApplicationCore
user32
user32
UnrealEditor_ApplicationCore
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
kernel32
ntdll

They worked perfectly fine in 5.6. I tried converting my Niagara Systems to standard emitters, but I can’t package my project because there’s a lightweight Niagara System somewhere and I can’t find it. Not sure what to do here.

2

Hey!

I had the exact same issue, it crashed 100% in 5.7.1 when saving a Niagara System with a lightweight/stateless emitter in it.

The crash is in FNiagaraEditorModule::PrecompileDuplicate l.1404 :

BasePtr->EmitterData[i]->FinishPrecompileDuplicate(EncounterableEmitterVariables, StaticVariablesFromEmitter, ConstantResolver, &Handle.GetEmitterData()->GetSimulationStages(), ((FNiagaraCompileRequestData*)OwningSystemRequestData)->EmitterData[i]->RapidIterationParams);

FNiagaraEmitterHandle::GetEmitterData returns null for stateless emitters.

Turns out I needed to change the compilation mode of Niagara scripts in project settings to “Async System Compilation” which doesn’t trigger compilation for stateless emitters. It was in “Serial Compilation“ which is deprecated.

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