Skinned Mesh Extractor

A Unity Editor tool for extracting meshes out of a GameObject hierarchy and saving them as standalone assets. Works with both MeshFilter and SkinnedMeshRenderer components, preserves bone weights and blendshapes, and can optionally rebuild the hierarchy as a prefab or export to FBX.

Installation

Drop all seven .cs files into an Editor/ folder anywhere inside your Unity project's Assets/. They share the MeshTools namespace and don't need to be in any particular subfolder.

Requires Unity 2020.1+ (uses Mesh.AcquireReadOnlyMeshData, GetAllBoneWeights, and GetBonesPerVertex).

Usage

1. Open the window via Tools → Skinned Mesh Extractor in the Unity menu bar.
2. Drag a GameObject from the scene or a prefab into the drop zone.
3. Configure options:
   • Output Folder — where extracted .asset meshes, prefabs, and (optionally) FBX files are written. Defaults to Assets/Mesh.
   • Rebuild In Scene — leave the rebuilt hierarchy as a new GameObject in the scene after extraction.
   • Save Prefab Asset — save the rebuilt hierarchy as a .prefab in the output folder.
   • Export FBX — also write a .fbx of the rebuilt hierarchy. Requires the com.unity.formats.fbx package; if it isn't installed, the tool will install it automatically via the Package Manager when you click Extract. NOTE: Having Export FBX toggled on will make the prefab use that fbx not the .asset files
4. Click Extract.

Each run writes to a timestamped subfolder like Assets/Mesh/run_20260421_143022_MyCharacter/ so runs don't overwrite each other.

How it works

For each mesh in the hierarchy, the tool picks the simplest path that will work:

• If the source mesh is marked Read/Write enabled, it clones the mesh directly via Object.Instantiate. This preserves all skinning data including things that are awkward to pull through the public C# API (bone indices, modern-format weight streams).
• If the source is not readable, the tool temporarily flips the ModelImporter.isReadable flag, reimports, extracts, and restores the original setting afterward.
• As a last resort, attributes are extracted individually (vertices, normals, UVs, tangents, colors, submeshes, bone weights via both legacy and modern APIs, bindposes, blendshapes) and a new Mesh is built from them.

Bone weights use a two-stage approach: the legacy mesh.boneWeights API first, falling back to GetAllBoneWeights / GetBonesPerVertex when the legacy API returns collapsed indices (which happens with meshes imported using "Unlimited" bones-per-vertex). Bindposes fall back to reconstruction from the SMR's bones array if the mesh doesn't expose them.

When rebuilding the hierarchy, bones are remapped by their path relative to the root (Armature/Hips/Spine, etc.), and bones and rootBone are set on the SMR before sharedMesh — Unity binds skinning at the moment sharedMesh is assigned, so ordering matters.

File layout

File	Responsibility
SkinnedMeshExtractor.cs	EditorWindow — UI, drag-drop, coroutine runner, Read/Write toggle orchestration
MeshSlot.cs	Shared data classes (MeshSlot, Attr, BlendShapeCapture, BlendShapeFrame)
MeshAttributeExtractor.cs	Pulls every attribute out of a source mesh, with fallbacks
MeshBuilder.cs	Turns an Attr into a saved .asset Mesh
HierarchyRebuilder.cs	Clones the GameObject hierarchy, remaps bones, saves prefab
FbxExporter.cs	Reflection-based wrapper around the Unity FBX Exporter package
MeshExtractorUtils.cs	Small static helpers (path building, vertex validation, folder/name utilities)

Only SkinnedMeshExtractorWindow is public. Everything else is internal to keep the surface area small.

Output

Inside each run folder:

• <MeshName>_extracted.asset — one per mesh in the hierarchy, always written
• <RootName>_extracted.prefab — if Save Prefab Asset is on
• <RootName>_extracted.fbx — if Save Prefab Asset and Export FBX are both on, and the FBX Exporter package is installed

Note: Export FBX only runs when Save Prefab Asset is also enabled. If both Rebuild In Scene and Save Prefab Asset are off, the hierarchy rebuild step is skipped entirely — you'll only get .asset files for the individual meshes.

Notes and caveats

• The tool flips Read/Write on source .fbx/.asset importers during a run and restores the original value in a finally block. If Unity crashes mid-extraction, you may need to check your import settings manually.
• FBX export is best-effort via reflection on UnityEditor.Formats.Fbx.Exporter.ModelExporter. If the Unity FBX Exporter package's API changes, export will log a warning and skip — the .asset and .prefab outputs will still succeed.
• Blendshape weights from the original SMR are copied onto the rebuilt SMR when the rebuilt mesh has matching blendshapes.
• Submesh triangles that throw on GetTriangles are silently skipped rather than aborting the whole extraction.
• Meshes with more than 65535 vertices are automatically switched to IndexFormat.UInt32 during the fallback rebuild path.