This has been fixed, and should be in 4.19.
This is a very bad news…
In the meantime, the workaround that
we have found is to wait a minute or
two after starting the editor before
entering VR Mode. That /should/ help
avoid crashes until the fix is
available.
Proposed WA does not fix the issue,
How long for 4.19 preview 1? :((
We do not have a time frame for the 4.19 preview. Unfortunately due to the nature of the change, it cannot be pushed to a 4.18 hotfix.
Is it feasible for you to make a change like Lee is suggesting?
No experience at all in engine modifications/recompile and a game launch in 30 days…
Is this occurring in a packaged game? We’ve only observed this in VR editing mode, so you should be able to use the standard desktop editing tools.
not sure what you mean: we’re experiencing it during pie vr preview
packaged game is fine, but we can’t test it in pie
never used vr editing mode
got it now: didn’t noticed main subject was referencing to vr mode, sorry
anyway all forum threads and issues I listed below are referencing to vr preview crashes.
this is a critical failure, totally blocking development and testing phase 
We’re dealing with same problem and it’s a crash in VR preview
For me the problem does occur in packaged builds and launching from the editor to the target.
Epic any news?
thanks
Any updates?
not able to get it built
2>SlateRHIRenderer.cpp.obj : error LNK2019: unresolved external symbol "public: struct FVector2D __cdecl FSlateWindowElementList::GetSizeInScreen(void)const " (?GetSizeInScreen@FSlateWindowElementList@@QEBA?AUFVector2D@@XZ) referenced in function "public: void __cdecl FSlateRHIRenderer::DrawWindow_RenderThread(class FRHICommandListImmediate &,struct FSlateRHIRenderer::FViewportInfo &,class FSlateWindowElementList &,bool,bool)" (?DrawWindow_RenderThread@FSlateRHIRenderer@@QEAAXAEAVFRHICommandListImmediate@@AEAUFViewportInfo@1@AEAVFSlateWindowElementList@@_N3@Z)
2>E:\GitHub\UnrealEngine\Engine\Binaries\Win64\UE4Editor-SlateRHIRenderer.dll : fatal error LNK1120: 1 unresolved externals
2>ERROR : UBT error : Failed to produce item: E:\GitHub\UnrealEngine\Engine\Binaries\Win64\UE4Editor-SlateRHIRenderer.dll
any suggestions?
thanks in advance
successfully built, editor seems ok now (I have a working commit on github)
thanks Lee for your valuable help
I think his reply should be marked as right answer.
Hope Epic will link UE-51146, UE-51727, UE-51883 to this thread and will fix that critical bug at least in 4.19…
I’m glad you were able to get it working! This issue is indeed fixed in 4.19: Unreal Engine Issues and Bug Tracker (UE-50445)
Thanks for the update!
I’ll be able to test the workaround tomorrow.
I was going to create new report but found this one. It seems like you’re working on this issue. I will attach few more crash logs. I think they all are related to the issue being discussed here and might be helpful. Some of them probably have been specified before.
Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x00000000
SWidget::SlatePrepass() []
FLayoutSaveRestore::PrepareLayoutStringForIni() []
FSlateApplication::DrawPrepass() []
FSlateApplication::PrivateDrawWindows() []
FSlateApplication::TickApplication() []
FSlateApplication::Tick() []
FEngineLoop::Tick() []
GuardedMain() []
GuardedMainWrapper() []
WinMain() []
Ensure condition failed: false [File:D:\Build\++UE4+Release-4.18+Compile\Sync\Engine\Source\Runtime\SlateRHIRenderer\Private\SlateRHIRenderer.cpp] [Line: 1072]
Window isnt valid but being drawn!
Stack:
FWindowsPlatformStackWalk::StackWalkAndDump() []
FDebug::EnsureFailed() []
FDebug::OptionallyLogFormattedEnsureMessageReturningFalse() []
FSlateRHIRenderer::DrawWindows_Private() []
FSlateApplication::PrivateDrawWindows() []
FSlateApplication::TickApplication() []
FSlateApplication::Tick() []
FEngineLoop::Tick() []
GuardedMain() []
GuardedMainWrapper() []
WinMain() []Same issue, have more logs
[2017.12.06-09.25.55:284][785]LogWindows: Error: === Critical error: ===
[2017.12.06-09.25.55:284][785]LogWindows: Error:
[2017.12.06-09.25.55:284][785]LogWindows: Error: Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0xffffffff
[2017.12.06-09.25.55:284][785]LogWindows: Error:
[2017.12.06-09.25.55:284][785]LogWindows: Error: [Callstack] 0x00000000DB17AF8D UE4Editor-SlateCore.dll!SWindow::IsVisible() [d:\build\++ue4+release-4.18+compile\sync\engine\source\runtime\slatecore\private\widgets\swindow.cpp:1326]
[2017.12.06-09.25.55:284][785]LogWindows: Error: [Callstack] 0x00000000C143662E UE4Editor-Slate.dll!PrepassWindowAndChildren() [d:\build\++ue4+release-4.18+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:1336]
[2017.12.06-09.25.55:284][785]LogWindows: Error: [Callstack] 0x00000000C1402D46 UE4Editor-Slate.dll!FSlateApplication::DrawPrepass() [d:\build\++ue4+release-4.18+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:1391]
[2017.12.06-09.25.55:284][785]LogWindows: Error: [Callstack] 0x00000000C1437389 UE4Editor-Slate.dll!FSlateApplication::PrivateDrawWindows() [d:\build\++ue4+release-4.18+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:1433]
[2017.12.06-09.25.55:284][785]LogWindows: Error: [Callstack] 0x00000000C1404140 UE4Editor-Slate.dll!FSlateApplication::DrawWindows() [d:\build\++ue4+release-4.18+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:1190]
[2017.12.06-09.25.55:284][785]LogWindows: Error: [Callstack] 0x00000000C145D867 UE4Editor-Slate.dll!FSlateApplication::TickApplication() [d:\build\++ue4+release-4.18+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:1777]good catch, I am also having this issue in VR Preview Mode
Wait wait wait, are you having this issue in VR Mode or VR Preview PIE Mode? It seems most of the commenters are the latter, but epic staff is assuming the former
This is sort of insane. The majority of the people here are having issues with VR Preview, meaning it’s basically impossible to test a VR game on UE4.18.1. This is a critical, development blocking bug and you’re telling us there’s no actual time table to get it fixed in a release? Everyone needs to just compile from source, a process requiring a full day and >60gb of hard drive space? Is it really more unacceptable to change BROKEN public headers than it is to screw over VR devs who just went through the process of upgrading to 4.18?
vr preview pie mode, told it loud and clear to epic (not sure they got it)
anyway fix reported by lee solved my problem with vr preview pie mode
I had to recompile engine, but was easier than I expected