UE5.6 - World Partition HLOD generation fails when StreamlineCore Plugin is enabled (UE5.6 - DLSS4 8.2.0 and 8.3.0)

Gaming and Visualization Technologies DLSS
1

This issue we have since we’ve upgraded our project from UE5.5.4 to UE5.6.1. The DLSS plugin(s) was already on DLSS4 8.2.0 on UE5.5.4.

I’ve just tested this with DLSS4Test project that comes with the DLSS4 8.3.0 plugin for UE5.6.

Steps to reproduce:

  • Create a Open World map using the “Open World” template
  • add some static meshes on it
  • start building HLODs

→ HLOD generation fails with the following errors:

LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.31:865][ 0]LogWindows: Error: appError called: Assertion failed: FSlateApplication::IsInitialized() [File:Z:_stage\UEDLSS4Plugins_5.6_v8.3.0-rc-b_2025-09-10\Plugins\StreamlineCore\HostProject\Plugins\StreamlineCore\Source\StreamlineCore\Private\StreamlineViewExtension.cpp] [Line: 189]
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.31:867][ 0]LogWindows: Error: Windows GetLastError: Das Handle ist ungültig. (6)
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:070][ 0]LogWindows: Error: === Critical error: ===
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:070][ 0]LogWindows: Error:
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:070][ 0]LogWindows: Error: Assertion failed: FSlateApplication::IsInitialized() [File:Z:_stage\UEDLSS4Plugins_5.6_v8.3.0-rc-b_2025-09-10\Plugins\StreamlineCore\HostProject\Plugins\StreamlineCore\Source\StreamlineCore\Private\StreamlineViewExtension.cpp] [Line: 189]
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:072][ 0]LogWindows: Error:
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:072][ 0]LogWindows: Error:
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:073][ 0]LogWindows: Error:
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:073][ 0]LogWindows: Error: [Callstack] 0x00007ffdabce4028 UnrealEditor-Core.dll!UnknownFunction
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:073][ 0]LogWindows: Error: [Callstack] 0x0000020b8bf26366 UnrealEditor-StreamlineCore.dll!FStreamlineViewExtension::FStreamlineViewExtension() [Z:_stage\UEDLSS4Plugins_5.6_v8.3.0-rc-b_2025-09-10\Plugins\StreamlineCore\HostProject\Plugins\StreamlineCore\Source\StreamlineCore\Private\StreamlineViewExtension.cpp:189]
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:075][ 0]LogWindows: Error: [Callstack] 0x0000020b8bf06354 UnrealEditor-StreamlineCore.dll!FSceneViewExtensions::NewExtension<FStreamlineViewExtension,FStreamlineRHI *>() [C:\packman-repo\chk\UnrealEngine\5.6.0-Win64\Engine\Source\Runtime\Engine\Public\SceneViewExtension.h:306]
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:077][ 0]LogWindows: Error: [Callstack] 0x0000020b8bf0583b UnrealEditor-StreamlineCore.dll!FStreamlineCoreModule::StartupModule() [Z:_stage\UEDLSS4Plugins_5.6_v8.3.0-rc-b_2025-09-10\Plugins\StreamlineCore\HostProject\Plugins\StreamlineCore\Source\StreamlineCore\Private\StreamlineCore.cpp:85]
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:078][ 0]LogWindows: Error: [Callstack] 0x00007ffdabe44b4b UnrealEditor-Core.dll!UnknownFunction
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:079][ 0]LogWindows: Error: [Callstack] 0x00007ffe88cffd74 UnrealEditor-Projects.dll!UnknownFunction
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:080][ 0]LogWindows: Error: [Callstack] 0x00007ffe88d1bdc4 UnrealEditor-Projects.dll!UnknownFunction
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:080][ 0]LogWindows: Error: [Callstack] 0x00007ffe88cff5f8 UnrealEditor-Projects.dll!UnknownFunction
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:081][ 0]LogWindows: Error: [Callstack] 0x00007ff6dcea8947 UnrealEditor.exe!UnknownFunction
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:082][ 0]LogWindows: Error: [Callstack] 0x00007ff6dce9e39c UnrealEditor.exe!UnknownFunction
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:082][ 0]LogWindows: Error: [Callstack] 0x00007ff6dce9e6ba UnrealEditor.exe!UnknownFunction
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:083][ 0]LogWindows: Error: [Callstack] 0x00007ff6dcea209e UnrealEditor.exe!UnknownFunction
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:083][ 0]LogWindows: Error: [Callstack] 0x00007ff6dceb4e44 UnrealEditor.exe!UnknownFunction
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:083][ 0]LogWindows: Error: [Callstack] 0x00007ff6dceb80fa UnrealEditor.exe!UnknownFunction
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:084][ 0]LogWindows: Error: [Callstack] 0x00007ffee0a5e8d7 KERNEL32.DLL!UnknownFunction
LogWorldPartitionEditor: Error: #### COMMANDLET OUTPUT >> [2025.09.18-10.03.38:085][ 0]LogWindows: Error:
LogWorldPartitionEditor: Error: #### END COMMANDLET OUTPUT ####

When disabling the StreamlineCore plugin (which also disables StreamlineReflex and StreamlineDLSSG) and restarting the editor, the HLOD generation works.

2

Is there a plan to fix this? I lost a lot of time before realizing this is why my HLOD builds were failing.

3

Just tagging along to ask if a fix is planned for this or if there is a workaround?
I am encountering the same issue. Disabling the plugin each time to build HLODs is also proving to be problematic as simply disabling the DLSS plugins via editor causes the project to crash on launch.

4

Also running in to this. Haven’t verified this yet but there is the command line param slnoviewextension used at line 84 of StreamlineCore.cpp in the 8.3.0 plugin

Try building HLODs from the commandlet and add -slnoviewextensionto the command line params

EDIT: This did not work. Not sure why. Instead I made this edit in StreamlineCore\Private\StreamlineCore.cpp:

After UE_LOG(LogStreamline, Log, TEXT(“%s Enter”), ANSI_TO_TCHAR(FUNCTION));

bool bIsUnattended = false;

#if WITH_EDITOR
bIsUnattended = FApp::IsUnattended() || IsRunningCommandlet() || GIsRunningUnattendedScript;
#endif

if (GetPlatformStreamlineSupport() == EStreamlineSupport::Supported && !bIsUnattended)

So Streamline won’t load if the engine is running as a commandlet (or in an unattended mode)

1 Like
5

Another (undocumented) solution is to CREATE a cvar named “r.Streamline.InitializePlugin” in the “StartupModule” function of one of your Editor module that is starting before “StreamlineCore” module.

As “StreamlineCore” loading phase is “PostEngineInit“, a module with a “Default” phase is ok.
For example:

void FMyEditorModule::StartupModule()
{
    // Disable DLSS in commandlet!
    if (IsRunningCommandlet())
    {
        // This is not documented, but the technique is to DECLARE a cvar named "r.Streamline.InitializePlugin", and set it to zero, BEFORE dlss plugins loading!
        ConsoleManager::Get().RegisterConsoleVariable(TEXT("r.Streamline.InitializePlugin"), 0, TEXT(""), ECVF_Default);
    }
}

But anyway, it’s clearly a bug in the plugin!

6

Hello
Thanks for the solution – it seems logical. Unfortunately, it doesn’t work for me. I’m using version 2025.09.16_UE5.6_DLSS4Plugin_v8.3.0 on UE 5.6.1.

I generally build HLODs using CMD, but when I try to do it in the editor, I also get the same error for Streamline.

I’m not very good at C++, but after the changes, the compilation worked correctly. DSLL itself works fine in the game – I’m just having trouble building HLODs.

Thank you in advance for any help!