# Alembic import as "Skeletal Mesh"

**URL:** <https://forums.unrealengine.com/t/alembic-import-as-skeletal-mesh/528405>\
**Category:** Virtual Production\
**Tags:** unreal-engine, UE5-0, UE4-26, UE4-27, question\
**Created:** [April 14, 2022, 3:10pm UTC](https://forums.unrealengine.com/t/alembic-import-as-skeletal-mesh/528405 "2022-04-14T15:10:52Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![cortek1](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/cortek1/32/582975_2.png) [@cortek1](https://forums.unrealengine.com/u/cortek1)\
**Post date:** [April 14, 2022, 3:10pm UTC](https://forums.unrealengine.com/t/alembic-import-as-skeletal-mesh/528405/1 "2022-04-14T15:10:52Z")

</div>

hihi all. I get crash after importing **Alembic** 800 frames as Skeletal Mesh. If 100~ frames, import without problems. How can this problem be solved?

Crash →   
Assertion failed: (Index \>= 0) & (Index \< ArrayNum) [File:D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Public\Containers/Array.h] [Line: 703] Array index out of bounds: 988073600 from an array of size 988073600

UE4Editor\_Core  
UE4Editor\_Core  
UE4Editor\_AlembicLibrary  
UE4Editor\_AlembicLibrary  
UE4Editor\_AlembicLibrary  
UE4Editor\_AlembicLibrary  
UE4Editor\_AlembicLibrary  
UE4Editor\_AlembicLibrary  
UE4Editor\_AlembicLibrary  
UE4Editor\_Core  
UE4Editor\_Core  
UE4Editor\_Core  
UE4Editor\_Core  
UE4Editor\_Core  
kernel32  
ntdll

---

<div class="post-metadata">

**Author:** ![cortek1](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/cortek1/32/582975_2.png) [@cortek1](https://forums.unrealengine.com/u/cortek1)\
**Post date:** [April 15, 2022, 7:50pm UTC](https://forums.unrealengine.com/t/alembic-import-as-skeletal-mesh/528405/2 "2022-04-15T19:50:09Z")

</div>

With **“Editor symbols for debugging”** I got this

Assertion failed: (Index \>= 0) & (Index \< ArrayNum) [File:D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Public\Containers/Array.h] [Line: 703] Array index out of bounds: 988073600 from an array of size 988073600

UE4Editor\_Core!AssertFailedImplV() [D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Private\Misc\AssertionMacros.cpp:104]  
UE4Editor\_Core!FDebug::CheckVerifyFailedImpl() [D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Private\Misc\AssertionMacros.cpp:461]  
UE4Editor\_AlembicLibrary!DispatchCheckVerify\<void,\<lambda\_171dde5f8e8bf0c6e06289e47e00b980\> \>() [D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Public\Misc\AssertionMacros.h:165]  
UE4Editor\_AlembicLibrary!AbcImporterUtilities::GenerateDeltaFrameDataMatrix() [D:\Build++UE4\Sync\Engine\Plugins\Experimental\AlembicImporter\Source\AlembicLibrary\Private\AbcImportUtilities.cpp:1216]  
UE4Editor\_AlembicLibrary!\<lambda\_bf0cf85dc4342a5998d863efde993431\>::operator()() [D:\Build++UE4\Sync\Engine\Plugins\Experimental\AlembicImporter\Source\AlembicLibrary\Private\AbcImporter.cpp:1205]  
UE4Editor\_AlembicLibrary!UE4Function\_Private::TFunctionRefCaller\<TFunction\<void \_\_cdecl(int,FAbcFile \*)\>,void \_\_cdecl(int,FAbcFile \*)\>::Call() [D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Public\Templates\Function.h:549]  
UE4Editor\_AlembicLibrary!\<lambda\_cc46014b65a5dcf61c74faf2be8aa74f\>::operator()() [D:\Build++UE4\Sync\Engine\Plugins\Experimental\AlembicImporter\Source\AlembicLibrary\Private\AbcFile.cpp:525]  
UE4Editor\_AlembicLibrary!ParallelForImpl::TParallelForData\<TFunctionRef\<void \_\_cdecl(int)\> \>::Process() [D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Public\Async\ParallelFor.h:177]  
UE4Editor\_AlembicLibrary!TGraphTask\<ParallelForImpl::TParallelForTask\<TFunctionRef\<void \_\_cdecl(int)\> \> \>::ExecuteTask() [D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Public\Async\TaskGraphInterfaces.h:886]  
UE4Editor\_Core!FTaskThreadAnyThread::ProcessTasks() [D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:1066]  
UE4Editor\_Core!FTaskThreadAnyThread::ProcessTasksUntilQuit() [D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:889]  
UE4Editor\_Core!FTaskThreadAnyThread::Run() [D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:966]  
UE4Editor\_Core!FRunnableThreadWin::Run() [D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Private\Windows\WindowsRunnableThread.cpp:86]

---

<div class="post-metadata">

**Author:** ![Andrej730](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/andrej730/32/1194692_2.png) [@Andrej730](https://forums.unrealengine.com/u/Andrej730)\
**Post date:** [April 16, 2022, 3:11pm UTC](https://forums.unrealengine.com/t/alembic-import-as-skeletal-mesh/528405/3 "2022-04-16T15:11:18Z")

</div>

Trying to debug it I’ve fugured that the problem lays is that TArray length is 32 based and it’s limited to 2,147,483,647. Since I have 2 093 952 normals each have 3 coords and 841 frames I get that I need = 5 283 040 896 long TArray. But because it’s 32 based, it overflows and this is where we get number 988073600 in the error 5 283 040 896 - 2 147 483 647 x 2 ~ 988 073 600.

So the question is - how do I make TArray length 64 int based?  
I’ve tried to use TArray64 but had no success (code example is below, output I got is “_Warning: DEBUG\_LOG: Zeroed 5283040896 matrices len 988075595_”).

```auto
    TArray64<float> DebugMatrices;
    int x = 528304089;

    DebugMatrices.AddZeroed(x*10);
    UE_LOG(LogTemp, Warning, TEXT("DEBUG_LOG: Zeroed 5 283 040 890 matrices len %d"), DebugMatrices.Num());

```

PS I’m working with @cortek1 on this issue

---

<div class="post-metadata">

**Author:** ![Andrej730](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/andrej730/32/1194692_2.png) [@Andrej730](https://forums.unrealengine.com/u/Andrej730)\
**Post date:** [June 8, 2023, 5:28pm UTC](https://forums.unrealengine.com/t/alembic-import-as-skeletal-mesh/528405/4 "2023-06-08T17:28:43Z")

</div>

Forgot to post update here. This problem is _kind of_ resolved by Epic Games here - [Unreal Engine Issues and Bug Tracker (UE-150964)](https://issues.unrealengine.com/issue/UE-150964)

What they basically did they replaced crash with alembic importer stop working when it reaches the limit and gives you error message that it won’t work. Basically what it means for cinematic production is that Alembic Skeletal Mesh pipeline is very unreliable given that it doesn’t support big meshes and Epic Games doesn’t seem to be interested in adding that support in the future (given the way they resolved that problem).