Issues with Groom Plugin: Project Fails to Open and Assertion Error on Binding Hair

General Issues and Bug Reporting
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1

Summary

I’m encountering two issues with the Groom plugin in Unreal Engine 5.4. First, the project fails to launch when the Groom plugin is enabled. When I manage to open the project, I receive an assertion error when attempting to bind hair to a MetaHuman mesh.

Please select what you are reporting on:

Creative

What Type of Bug are you experiencing?

Assets

Steps to Reproduce

Steps to Reproduce:

Enable the Groom plugin in the project.
Try to open the project (project fails to open).
Disable the plugin, delete Saved, Intermediate, and Cache folders, and open the project successfully.
Re-enable the Groom plugin.
Attempt to bind the Groom hair to a MetaHuman mesh.
Receive an assertion error.

Expected Result

The project should open without any issues with the Groom plugin enabled.
The hair should bind correctly to the MetaHuman mesh without errors.

Observed Result

The project fails to open when the Groom plugin is enabled, with the following error:
Fatal error: [File:D:\build++UE5\Sync\Engine\Source\Runtime\Core\Private\Containers\ContainerHelpers.cpp] [Line: 8] Trying to resize TArray to an invalid size of 3738140416

When I manage to open the project, attempting to bind the hair causes the following assertion error:
Assertion failed: CellIndex < uint32(Cells.Num()) [File:D:\build++UE5\Sync\Engine\Plugins\Runtime\HairStrands\Source\HairStrandsCore\Private\GroomBindingBuilder.cpp] [Line: 932]

Platform(s)

Windows

Additional Notes

The project was working fine with the Groom plugin a few days ago, and I haven’t made any major changes since then. I’ve tried basic troubleshooting steps like disabling the plugin, deleting cache files, and re-enabling it, but the issue persists.

I tried deleting the metahuman, adding it in a new project, but the problem does not go away. When binding to mesh, the project crashes

2

Hello everyone,

I’ve been running into a couple of issues with the Groom plugin in my Unreal Engine 5.4 project. Initially, the project wouldn’t open when the Groom plugin was enabled. The only hair in the project is from a MetaHuman. Here’s the error message I received when the project failed to launch:

Fatal error: [File:D:\build\++UE5\Sync\Engine\Source\Runtime\Core\Private\Containers\ContainerHelpers.cpp] [Line: 8] Trying to resize TArray to an invalid size of 3738140416

I managed to temporarily fix the issue by disabling the plugin in the .uproject file and deleting the Saved, Intermediate, and Cache folders. However, today the project opened successfully with the Groom plugin enabled, but now I’m facing a new issue when trying to bind the hair to the mesh. I get the following error:

Assertion failed: CellIndex < uint32(Cells.Num()) [File:D:\build\++UE5\Sync\Engine\Plugins\Runtime\HairStrands\Source\HairStrandsCore\Private\GroomBindingBuilder.cpp] [Line: 932]

Has anyone else experienced these issues or knows a solution? The Groom plugin was working fine just a few days ago, so I’m not sure what changed.

Any help would be greatly appreciated. Thank you!

3

The error:

Assertion failed: CellIndex < uint32(Cells.Num()) [File:D:\build\++UE5\Sync\Engine\Plugins\Runtime\HairStrands\Source\HairStrandsCore\Private\GroomBindingBuilder.cpp] [Line: 932]

occurs specifically when there are groom binding files in the project. As soon as I delete these binding files, the project opens fine. However, when I recreate the binding, the project crashes again.