Getting a crash with "Trying to access current bone buffer for reading, but it is null."

Development Programming & Scripting
,
1

This occurred after I added cloth physics to a characters LOD. It was present before, generating LODs and adding the physics to it has caused this.

It only happens when playing the game, everything is working perfectly fine, and after some indeterminate period of time, it crashes. I have a guess it might be at the point the LOD levels switch, unsure.

Assertion failed: bPrevious [File:D:\build++UE5\Sync\Engine\Source\Runtime\Engine\Public\GPUSkinVertexFactory.h] [Line: 247] Trying to access current bone buffer for reading, but it is null. BoneBuffer[0] = 0000000000000000, BoneBuffer[1] = 0000000000000000, CurrentRevisionNumber = 0, PreviousRevisionNumber = 0

2

Edit: This did not work :frowning:

Delved into the crashing cpp header file, since “bone buffer” is referenced just about nowhere on the internet. Didn’t help.

Ended up simply regenerating LOD2, and regenerating the clothing LOD, replacing it without parameter remap. No clue why, but I haven’t gotten THAT crash since. INSTEAD, I then got this:

Assertion failed : IntFitsIn <OutType >(In) [File :D:\build++UE5 *Sync* … h ] [Line : 163] Loss of data caused by narrowing conversion .

Which is strange. I ended up doing the aforementioned fix a couple more times. Having “Merge Coincident Vertex Bones” set to off made this crash not happen. If this merged bones that would make sense to cause a crash on reference to a bone buffer, but it merges bone WEIGHTS.

I assume that having this boolean set differently between generated LODS causes this issue.

3

Nevermind. The crash happened again. Still no clue why.

4

Some combination of having LODs, cloth physics on LODs, and pausing/resuming cloth simulation causes this crash.

LOD 0
cape - cloth physics
clothing - cloth physics

LOD 1
cape - cloth physics LOD1
clothing - No LOD applied ( on purpose )

This setup causes the crash. For reference I was querying each frame to see if was viewable and pausing it off screen. Some combination of these things causes one of the aforementioned crashes, unpredictable which it is.

5

Bump. Crash still happens with " > Assertion failed : IntFitsIn <OutType >(In) [File :D:\build++UE5 Sync … h ] [Line : 163] Loss of data caused by narrowing conversion ."

Randomly crashes engine, but its very rare now.

6

Bump

7

Bump

8

Bump

9

With editor symbols now. Error looks like this:

Assertion failed: IntFitsIn(In) [File:D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Templates\UnrealTemplate.h] [Line: 174] Loss of data caused by narrowing conversion, In = -4611686018427387904

UnrealEditor_Renderer!UE::Math::TIntVector3::TIntVector3<__int64>() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Math\IntVector.h:104]
UnrealEditor_Renderer!FSceneCullingBuilder::ProcessPostSceneUpdate() [D:\build++UE5\Sync\Engine\Source\Runtime\Renderer\Private\SceneCulling\SceneCulling.cpp:2418]
UnrealEditor_Renderer!FComputeShaderUtils::AddPass<FSceneCullingDebugRender_CS>'::2’::<lambda_1>::operator()() [D:\build++UE5\Sync\Engine\Source\Runtime\RenderCore\Public\RenderGraphBuilder.inl:550]
UnrealEditor_Renderer!UE::Tasks::Private::FTaskBase::TryExecuteTask() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Tasks\TaskPrivate.h:504]
UnrealEditor_Renderer!LowLevelTasks::TTaskDelegate<LowLevelTasks::FTask * __ptr64 __cdecl(bool),48>::TTaskDelegateImpl<LowLevelTasks::FTask::Init<UE::Tasks::Private::FTaskBase::Init’::2'::<lambda_1> >'::13’::<lambda_1>,0>::CallAndMove() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Async\Fundamental\TaskDelegate.h:171]
UnrealEditor_Core!LowLevelTasks::FTask::ExecuteTask() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Async\Fundamental\Task.h:627]
UnrealEditor_Core!LowLevelTasks::FScheduler::ExecuteTask() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Private\Async\Fundamental\Scheduler.cpp:155]
UnrealEditor_Core!LowLevelTasks::FScheduler::WorkerMain() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Private\Async\Fundamental\Scheduler.cpp:397]
UnrealEditor_Core!UE::Core::Private::Function::TFunctionRefCaller<LowLevelTasks::FScheduler::CreateWorker'::2’::<lambda_1>,void __cdecl(void)>::Call() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Templates\Function.h:406]
UnrealEditor_Core!FThreadImpl::Run() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Private\HAL\Thread.cpp:69]
UnrealEditor_Core!FRunnableThreadWin::Run() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Private\Windows\WindowsRunnableThread.cpp:149]