Crash when importing model in UE5.7.0 pre (mesh description is empty, Array index out of bounds) #548
Description
Describe the bug
Hello,
I encountered a crash when importing a .pmx model in Unreal Engine 5.7 using VRM4U(VRM4U version: 20250925).
The editor crashes right after opening the imported SkeletalMesh asset.
Error message from log:
Assertion failed: (Index >= 0) & (Index < ArrayNum)
Array index out of bounds: 0 into an array of size 0
LogAnimation: Error: Skeleton Modifier: mesh description is empty.
It seems that the imported SkeletalMesh (SK_lan) has an empty mesh description.
There are also multiple warnings during import:
LogImageWrapper: Error: Bmp header invalid
LoadErrors: Missing dependency /Engine/EngineMeshes/Humanoid
Steps to Reproduce:
Open UE 5.7 with VRM4U enabled.
Import a .pmx model (e.g. lan.pmx).
Finish import options and confirm.
Try to open the generated SkeletalMesh asset → Editor crashes.
Expected Behavior:
The PMX model should import successfully and open in the SkeletalMesh editor.
Actual Behavior:
The imported SkeletalMesh has no valid mesh data, and opening it crashes UE.
Screenshots, log
[2025.10.05-06.10.06:407][ 39]LogFactory: FactoryCreateFile: SkeletalMesh with VRM4UImporterFactory (0 0 C:\Users\Administrator\Desktop\lan\lan.pmx)
[2025.10.05-06.10.06:408][ 39]LogVRM4ULoader: GetVRMMeta:OrigFileName=C:\Users\Administrator\Desktop\lan\lan.pmx
[2025.10.05-06.10.06:408][ 39]LogVRM4ULoader: GetVRMMeta:std::stringFileName=C:\Users\Administrator\Desktop\lan\lan.pmx
[2025.10.05-06.10.06:408][ 39]LogVRM4ULoader: GetVRMMeta: filesize=2473265
[2025.10.05-06.10.07:066][ 39]LogVRM4ULoader: GetVRMMeta: mScenePtr=000001F3ECEA91F0
[2025.10.05-06.10.10:668][ 39]LogSlate: Window 'VRM Import Options' being destroyed
[2025.10.05-06.10.13:749][ 39]LogVRM4ULoader: VRM:(2.957 secs) ReadFileFromMemory
[2025.10.05-06.10.13:754][ 39]LogVRM4ULoader: VRM:(0.01 secs) Begin convert
[2025.10.05-06.10.13:779][ 39]LogVRM4ULoader: VRM:(0.02 secs) NormalizeBoneName
[2025.10.05-06.10.13:780][ 39]LogImageWrapper: Error: Bmp header invalid
[2025.10.05-06.10.13:803][ 39]LogImageWrapper: Error: Bmp header invalid
[2025.10.05-06.10.13:826][ 39]LogImageWrapper: Error: Bmp header invalid
[2025.10.05-06.10.13:848][ 39]LogImageWrapper: Error: Bmp header invalid
[2025.10.05-06.10.13:870][ 39]LogImageWrapper: Error: Bmp header invalid
[2025.10.05-06.10.13:898][ 39]LogImageWrapper: Error: Bmp header invalid
[2025.10.05-06.10.13:924][ 39]LogImageWrapper: Error: Bmp header invalid
[2025.10.05-06.10.13:951][ 39]LogImageWrapper: Error: Bmp header invalid
[2025.10.05-06.10.13:985][ 39]LogImageWrapper: Error: Bmp header invalid
[2025.10.05-06.10.14:015][ 39]LogImageWrapper: Error: Bmp header invalid
[2025.10.05-06.10.14:444][ 39]LogVRM4ULoader: VRM:(0.67 secs) ConvertTextureAndMaterial
[2025.10.05-06.10.14:472][ 39]LogVRM4ULoader: VRM:(0.03 secs) ConvertVrmMeta
[2025.10.05-06.10.14:702][ 39]LogAsyncCompilation: Display: AddQueuedWork [No DebugName] did not supply a RequiredMemory estimate. This is a bug, all asset types should provide an estimate. When no estimate is provided asset compilation is slowed as the queue has to operate very conservatively.
[2025.10.05-06.10.14:703][ 39]LogSkeletalMesh: Building Skeletal Mesh SK_lan...
[2025.10.05-06.10.14:720][ 39]LogSkinnedAsset: Display: Waiting for skinned assets to be ready 0/1 (SK_lan) ...
[2025.10.05-06.10.14:803][ 39]LogSkeletalMesh: Built Skeletal Mesh [0.10s] /Game/lan/SK_lan.SK_lan
[2025.10.05-06.10.14:824][ 39]LogAsyncCompilation: Display: AddQueuedWork [No DebugName] did not supply a RequiredMemory estimate. This is a bug, all asset types should provide an estimate. When no estimate is provided asset compilation is slowed as the queue has to operate very conservatively.
[2025.10.05-06.10.14:824][ 39]LogSkeletalMesh: Building Skeletal Mesh SK_lan...
[2025.10.05-06.10.14:840][ 39]LogSkinnedAsset: Display: Waiting for skinned assets to be ready 0/1 (SK_lan) ...
[2025.10.05-06.10.14:921][ 39]LogSkeletalMesh: Built Skeletal Mesh [0.10s] /Game/lan/SK_lan.SK_lan
[2025.10.05-06.10.15:005][ 39]LogUObjectHash: Compacting FUObjectHashTables data took 0.79ms
[2025.10.05-06.10.15:075][ 39]LogSkinnedAsset: Display: Waiting for skinned assets to be ready 0/1 (SK_VRoidSimple) ...
[2025.10.05-06.10.15:100][ 39]LogUObjectHash: Compacting FUObjectHashTables data took 0.80ms
[2025.10.05-06.10.15:102][ 39]LogAsyncCompilation: Display: AddQueuedWork [No DebugName] did not supply a RequiredMemory estimate. This is a bug, all asset types should provide an estimate. When no estimate is provided asset compilation is slowed as the queue has to operate very conservatively.
[2025.10.05-06.10.15:102][ 39]LogSkeletalMesh: Building Skeletal Mesh SK_lan...
[2025.10.05-06.10.15:102][ 39]LogVRM4ULoader: VRM:(0.63 secs) ConvertModel
[2025.10.05-06.10.15:118][ 39]LogSkinnedAsset: Display: Waiting for skinned assets to be ready 0/1 (SK_lan) ...
[2025.10.05-06.10.15:199][ 39]LogSkeletalMesh: Built Skeletal Mesh [0.10s] /Game/lan/SK_lan.SK_lan
[2025.10.05-06.10.15:220][ 39]LogVRM4ULoader: VRM:(0.12 secs) ConvertRig
[2025.10.05-06.10.15:569][ 39]LogSkeletalMesh: Building Skeletal Mesh SKM_Manny...
[2025.10.05-06.10.15:638][ 39]LogSkinnedAsset: Display: Waiting for skinned assets to be ready 0/1 (SKM_Manny) ...
[2025.10.05-06.10.16:961][ 39]LogSkeletalMeshReduction: Reducing skeletal mesh for LOD 2
[2025.10.05-06.10.16:961][ 39]LogSkeletalMeshReduction: Reducing skeletal mesh for LOD 3
[2025.10.05-06.10.20:186][ 39]LogSkeletalMesh: Skeletal mesh [/Game/Characters/Mannequins/Meshes/SKM_Manny.SKM_Manny]: The derived data key is different after the build. Save the asset to avoid rebuilding it everytime the editor load it.
[2025.10.05-06.10.20:201][ 39]LogSkeletalMesh: Built Skeletal Mesh [4.63s] /Game/Characters/Mannequins/Meshes/SKM_Manny.SKM_Manny
[2025.10.05-06.10.20:273][ 39]LogSkinnedAsset: Display: Waiting for skinned assets to be ready 0/1 (SK_Mannequin) ...
[2025.10.05-06.10.20:371][ 39]LogStreaming: Warning: LoadPackage: SkipPackage: /Game/Characters/UEFN_Mannequin/Rigs/IK_UEFN_Mannequin (0xE3E1BA228E837C2B) - The package to load does not exist on disk or in the loader
[2025.10.05-06.10.20:371][ 39]LogUObjectGlobals: Warning: Failed to find object 'Object /Game/Characters/UEFN_Mannequin/Rigs/IK_UEFN_Mannequin.IK_UEFN_Mannequin'
[2025.10.05-06.10.20:371][ 39]LogVRM4ULoader: VRM:(5.15 secs) ConvertIKRig
[2025.10.05-06.10.20:437][ 39]LogAsyncCompilation: Display: AddQueuedWork [No DebugName] did not supply a RequiredMemory estimate. This is a bug, all asset types should provide an estimate. When no estimate is provided asset compilation is slowed as the queue has to operate very conservatively.
[2025.10.05-06.10.20:437][ 39]LogSkeletalMesh: Building Skeletal Mesh SK_lan...
[2025.10.05-06.10.20:454][ 39]LogSkinnedAsset: Display: Waiting for skinned assets to be ready 0/1 (SK_lan) ...
[2025.10.05-06.10.20:531][ 39]LogSkeletalMesh: Built Skeletal Mesh [0.09s] /Game/lan/SK_lan.SK_lan
[2025.10.05-06.10.20:551][ 39]LogAsyncCompilation: Display: AddQueuedWork [No DebugName] did not supply a RequiredMemory estimate. This is a bug, all asset types should provide an estimate. When no estimate is provided asset compilation is slowed as the queue has to operate very conservatively.
[2025.10.05-06.10.20:552][ 39]LogSkeletalMesh: Building Skeletal Mesh SK_lan...
[2025.10.05-06.10.20:568][ 39]LogSkinnedAsset: Display: Waiting for skinned assets to be ready 0/1 (SK_lan) ...
[2025.10.05-06.10.20:664][ 39]LogSkeletalMesh: Built Skeletal Mesh [0.11s] /Game/lan/SK_lan.SK_lan
[2025.10.05-06.10.20:691][ 39]LogAsyncCompilation: Display: AddQueuedWork [No DebugName] did not supply a RequiredMemory estimate. This is a bug, all asset types should provide an estimate. When no estimate is provided asset compilation is slowed as the queue has to operate very conservatively.
[2025.10.05-06.10.20:691][ 39]LogSkeletalMesh: Building Skeletal Mesh SK_lan...
[2025.10.05-06.10.20:691][ 39]LogVRM4ULoader: VRM:(0.32 secs) ConvertMorphTarget
[2025.10.05-06.10.20:707][ 39]LogSkinnedAsset: Display: Waiting for skinned assets to be ready 0/1 (SK_lan) ...
[2025.10.05-06.10.20:808][ 39]LogSkeletalMesh: Built Skeletal Mesh [0.12s] /Game/lan/SK_lan.SK_lan
[2025.10.05-06.10.20:845][ 39]LogScript: Warning: Script Msg: /Game/lan/A_face_lan : Insufficient precision while converting between frame rates 30 fps and 1 s: previous number of frames 1, converted frame-time 0.03333334
[2025.10.05-06.10.20:860][ 39]LogAnimationCompression: Display: Building compressed animation data for AnimSequence /Game/lan/A_face_lan.A_face_lan (Required Memory Estimate: 0.22 MB)
[2025.10.05-06.10.20:862][ 39]LogVRM4ULoader: VRM:(0.17 secs) ConvertPose
[2025.10.05-06.10.20:862][ 39]LogVRM4ULoader: VRM:(0.00 secs) ConvertHumanoid
[2025.10.05-06.10.20:862][ 39]LogVRM4ULoader: VRM:(0.00 secs) BeginSave
[2025.10.05-06.10.20:862][ 39]LogAnimationCompression: Display: Building compressed animation data for AnimSequence /Game/lan/A_face_lan.A_face_lan (Required Memory Estimate: 0.22 MB)
[2025.10.05-06.10.20:872][ 39]LogAnimationCompression: Display: Storing compressed animation data for /Game/lan/A_face_lan.A_face_lan, at AnimationSequence/71c63eeb121f6a9f152672983fdca7822d045275
[2025.10.05-06.10.20:903][ 39]LogAsyncCompilation: Display: AddQueuedWork [No DebugName] did not supply a RequiredMemory estimate. This is a bug, all asset types should provide an estimate. When no estimate is provided asset compilation is slowed as the queue has to operate very conservatively.
[2025.10.05-06.10.20:903][ 39]LogSkeletalMesh: Building Skeletal Mesh SK_lan...
[2025.10.05-06.10.20:919][ 39]LogSkinnedAsset: Display: Waiting for skinned assets to be ready 0/1 (SK_lan) ...
[2025.10.05-06.10.21:016][ 39]LogSkeletalMesh: Built Skeletal Mesh [0.11s] /Game/lan/SK_lan.SK_lan
[2025.10.05-06.10.21:034][ 39]LogVRM4ULoader: VRM:(0.17 secs) Save
[2025.10.05-06.10.21:100][ 39]LogUObjectHash: Compacting FUObjectHashTables data took 0.77ms
[2025.10.05-06.10.21:166][ 39]LogSlate: Took 0.000164 seconds to synchronously load lazily loaded font '../../../Engine/Content/Slate/Fonts/Roboto-Light.ttf' (167K)
[2025.10.05-06.10.21:174][ 39]LogSlate: Took 0.000760 seconds to synchronously load lazily loaded font '../../../Engine/Content/Slate/Fonts/DroidSansFallback.ttf' (3848K)
[2025.10.05-06.10.21:189][ 39]LoadErrors: Warning: While trying to load package /VRM4U/Util/BaseCharacter/Mesh/SKEL_VRoidSimple, a dependent package /Engine/EngineMeshes/Humanoid was not available. Additional explanatory information follows:
FPackageName: Skipped package /Engine/EngineMeshes/Humanoid has a valid, mounted, mount point but does not exist either on disk or in iostore. The uncooked file would be expected on disk at 'D:/App/Epic Games/UE_5.7/Engine/Content/EngineMeshes/Humanoid'. Perhaps it has been deleted or was not synced?
[2025.10.05-06.10.21:257][ 40]LogRenderer: Recreating Persistent SBTs due to initializer changes:
NumShaderSlotsPerGeometrySegment changed: current: 1 - new: 2
NumGeometrySegments changed: current: 0 - new: 512
[2025.10.05-06.10.21:453][ 42]LogRenderer: Recreating Persistent SBTs due to initializer changes:
NumShaderSlotsPerGeometrySegment changed: current: 1 - new: 2
NumGeometrySegments changed: current: 0 - new: 512
[2025.10.05-06.10.21:455][ 42]LogRenderer: Using fallback RTPSO
[2025.10.05-06.10.22:121][ 75]LogRenderer: Recreating Persistent SBTs due to initializer changes:
NumShaderSlotsPerGeometrySegment changed: current: 1 - new: 2
NumGeometrySegments changed: current: 0 - new: 512
[2025.10.05-06.10.22:244][ 79]LogRenderer: Recreating Persistent SBTs due to initializer changes:
NumShaderSlotsPerGeometrySegment changed: current: 1 - new: 2
NumGeometrySegments changed: current: 0 - new: 512
[2025.10.05-06.10.22:434][ 83]LogRenderer: Recreating Persistent SBTs due to initializer changes:
NumShaderSlotsPerGeometrySegment changed: current: 1 - new: 2
NumGeometrySegments changed: current: 0 - new: 512
[2025.10.05-06.10.22:436][ 83]LogRenderer: Using fallback RTPSO
[2025.10.05-06.10.22:470][ 84]LogRenderer: Recreating Persistent SBTs due to initializer changes:
NumShaderSlotsPerGeometrySegment changed: current: 1 - new: 2
NumGeometrySegments changed: current: 0 - new: 512
[2025.10.05-06.10.22:498][ 85]LogRenderer: Recreating Persistent SBTs due to initializer changes:
NumShaderSlotsPerGeometrySegment changed: current: 1 - new: 2
NumGeometrySegments changed: current: 0 - new: 512
[2025.10.05-06.10.23:986][161]LogAssetEditorSubsystem: Opening Asset editor for SkeletalMesh /Game/lan/SK_lan.SK_lan
[2025.10.05-06.10.23:995][161]LogStreaming: Display: FlushAsyncLoading(375): 1 QueuedPackages, 0 AsyncPackages
[2025.10.05-06.10.24:022][161]LogActorComponent: RegisterComponentWithWorld: (/Engine/Transient.World_7:PersistentLevel.AnimationEditorPreviewActor_0.DebugSkelMeshComponent_0) Already registered. Aborting.
[2025.10.05-06.10.24:349][161]LogAnimation: Error: Skeleton Modifier: mesh description is emtpy.
[2025.10.05-06.10.24:349][161]LogOutputDevice: Warning:
Script Stack (0 frames) :
[2025.10.05-06.10.24:361][161]LogWindows: Error: appError called: Assertion failed: (Index >= 0) & (Index < ArrayNum) [File:D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Containers\Array.h] [Line: 1096]
Array index out of bounds: 0 into an array of size 0
[2025.10.05-06.10.24:361][161]LogWindows: Windows GetLastError: The operation completed successfully. (0)
UnrealEngine Version:
Unreal Engine: 5.7.0
Additional context
The same PMX imports correctly in UE 5.1
When upgrading from an older project, the asset still exists internally (can be opened through references),
but it becomes invisible in Content Browser.