Mutable: Assertion failed: MipIndex >= 0 [File:D:\build\++UE5\Sync\Engine\Plugins\Mutable\Source\CustomizableObject\Private\MuCO\UnrealMutableImageProvider.cpp] [Line: 159]

Development Programming & Scripting
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Hi.

I’ve recently been working on a simple character customization system using the Mutable plugin. Everything works as expected in PIE/Standalone, so I decided to package the project to make sure it all works there too.

When I package the project it crashes as soon as a customizable character is loaded with the message: Assertion failed: MipIndex >= 0 [File:D:\build++UE5\Sync\Engine\Plugins\Mutable\Source\CustomizableObject\Private\MuCO\UnrealMutableImageProvider.cpp] [Line: 159]

I can see that the character loaded only contains a part of the default meshes it should have (only the base body, no outfit parts visible - I dont have any cloth physics enabled or clothing setting enabled on the customizable object items)

My customizable objects make use of enums/floats/colors/texture parameter pins. (tex param pins are marked as experimental, and because of the 'mips’ mentioned in the error I suspect it has something to do with that, but even after disabling all of those pins and re-packaging, the same error remains)

I’m using UE 5.7.2, with mutable 1.8.

Any insight into what I could do to resolve this issue would be greatly appreciated.

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It may be failing because it’s expecting an packaged on-disk Texture2D for that async load function if you’re not in editor. The in editor block above your assert uses the data in memory so it won’t fail for a dynamically generated texture. I’m not super familiar with Mutable, but that’s my gut feeling looking over where you’re failing the assert.

Now, how to go about fixing this.. not sure. Maybe a setup issue or you may have to include a base texture to start from? Hopefully that helps a bit.

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It seems like the issue was some of the materials on the mesh parts used virtual textures..

After converting all textures from VT to regular, which I was doing since I read VT support in mutable isnt strong yet, I repackaged, and the character loads properly, all meshes, no error/crash. :slight_smile:

Hopefully this info will help someone else along their journey <3

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