# Rigging
## Bone Skinning and Weight Painting
This guide explains the optional Bone Skinning and Weight Painting module for the `Equipment Fit Sculptor`.
The module adds a `Skinning` tab to the sculptor. It lets you inspect, transfer, paint, edit, create, and remove skin bones directly inside the Unity Editor for both character body meshes and equipment meshes.
### What This Module Does
The Skinning tab is intended for editor-time rig correction and weight authoring.
You can use it to:
* import the current designer-authored skin weights into an editable mesh asset
* inspect weight influence with a heat-map overlay
* paint bone weights directly in Scene view
* mirror weight painting with symmetry
* normalize weights after manual edits
* transfer body weights to one selected equipment mesh
* transfer body weights to all loaded equipment meshes
* replace an equipment rig with only the character bones that are actually used by that equipment
* create new bones
* insert a new bone between an existing parent bone and an optional end bone
* remove a bone from the renderer skin list and remap its weights to a fallback bone
* move, rotate, and scale selected bones through Unity scene handles
* save the edited mesh asset back to the project and prefab
### What This Module Is Not
This module is not a full DCC replacement.
Do not treat it as:
* a replacement for Blender, Maya, DAZ Studio, or a production rigging package
* a general animation retargeting system
* a cloth simulation authoring tool
* a tool for changing mesh topology
* a tool for authoring complex IK/FK controller rigs
* a safe way to experiment on original FBX assets without backups
The module is best used for common Character Creator workflows: correcting equipment deformation, transferring body weights to clothing, trimming an equipment rig down to the character bone subset, adding small helper bones, and fixing local weight mistakes.
### Optional Module Behavior
The Skinning tab only appears when the Skinning add-on module is present in the project.
In source form, the module lives under:
```
Assets/Arawn/CrystalCharacterCreator/Editor/Modules/Skinning
```
### Requirements
Before using the Skinning tab, make sure:
* the selected object has an `EquipmentManager`
* the Equipment Fit Sculptor can load the body and equipment renderers
* the target mesh is a `SkinnedMeshRenderer`
* the source mesh can be made readable
* the renderer has a valid `sharedMesh`
* the renderer has bones when you want to paint existing weights
* the body renderer has valid weights if you want to transfer body weights
* the sculptor preview is correctly aligned before transfer or auto-rig operations
The module can create an editable mesh copy when the current mesh is not directly editable. If the source mesh is imported from an FBX and Read/Write is disabled, the module attempts to enable Read/Write through the model importer and reimport the asset. If Unity cannot make the mesh readable, the operation fails with an error instead of modifying an unsafe mesh.
### Recommended Workflow
For most equipment, use this order:
1. Open the `Equipment Fit Sculptor` from the `EquipmentManager`.
2. Select the equipment mesh in the sculptor.
3. Confirm the preview is aligned with the body.
4. Open the `Skinning` tab.
5. Click `Import Current Weights To Editable Mesh`.
6. Use `Show Weight Overlay` to inspect current weights.
7. If this is cross-rig clothing, use `Auto-Rig Target To Character Bone Subset` or `Replace Bones With Character Subset + Transfer Weights`.
8. Paint corrections with `Paint In Scene`.
9. Use `Normalize Weights`.
10. Click `Save Mesh Asset`.
11. Test in play mode with the expected animation poses.
Do not skip the play mode test. Skinning can look correct in a neutral pose and still collapse during elbow, shoulder, hip, knee, or spine animation.
### Data Model
The Skinning tab does not overwrite the original imported FBX mesh directly.
When you click `Import Current Weights To Editable Mesh`, the module creates a generated editable mesh asset under:
```
Assets/Arawn/CrystalCharacterCreator/Generated/Skinning
```
The generated mesh is then assigned to the active renderer and, for equipment prefab targets, written back to the prefab renderer.
This means:
* the original model import asset remains intact
* the edited mesh asset becomes the skinning source used by the prefab
* changes to weights, bindposes, and generated bone assignments are stored in the generated mesh asset
* the generated mesh asset must stay in the Unity project if the prefab depends on it
* generated assets are authoring output and are not part of the core DLL source export
Use version control before large rig edits. Generated mesh assets are safer than editing imported FBX data directly, but they are still project assets.
### Opening The Skinning Tab
1. Select a character with `EquipmentManager`.
2. Expand an equipment entry.
3. Click `Open Equipment Fit Sculptor`.
4. Select the desired target in the sculptor.
5. Click the `Skinning` tab.
The tab is available for body meshes and equipment meshes. Some buttons are disabled for the body because the body is the source rig for transfer operations.
### Scene Visualization
When the Skinning tab is active, the Scene view draws bone guides through the mesh.
| Color | Meaning |
| ---------- | ------------------------------------------------------ |
| Black | Character body bones |
| Light blue | Equipment bones assigned to loaded equipment renderers |
| Red | Currently selected paint/edit bone |
Bones are drawn as wire pylon shapes, similar in purpose to Blender or DAZ-style bone display. They are drawn through the mesh so they remain visible even when they are inside the character or equipment.
If a bone has a parent or child in the assigned skin bone list, the pylon is drawn between the related joints. If a bone has no visible child segment, the tool draws a short leaf pylon from the bone transform so the selected bone is still visible.
### Scene Controls
#### Weight Painting
When `Paint In Scene` is enabled:
* `LMB drag` adds weight to the selected `Paint Bone`
* `Shift + LMB drag` subtracts weight from the selected `Paint Bone`
* `Alt` is left for Scene view navigation
* the brush disc is blue when adding
* the brush disc is red when subtracting
* symmetry draws a second brush disc on the mirrored side
Painting only works on editable generated mesh assets. If the selected mesh is still the original imported model mesh, click `Import Current Weights To Editable Mesh` first.
#### Bone Transform Handles
When a bone is selected in the Skinning tab, Unity transform tools can edit that bone:
* Move tool changes the bone world position
* Rotate tool changes the bone world rotation
* Scale or Rect tool changes the bone local scale
The local transform fields in the tab are still available for precise numeric edits.
Be careful with scale, especially non-uniform scale. Bone scaling can be useful for helper bones, but it can also produce unexpected deformation, cloth behavior, or animation differences on some rigs. Prefer moving or rotating bones unless scale is truly required.
### UI Reference
#### Target Mesh
`Target Mesh` chooses which loaded body or equipment renderer the Skinning tab edits.
Use it when:
* multiple equipment meshes are loaded
* an equipment prefab contains multiple `SkinnedMeshRenderer`s
* you need to switch between body and equipment weight inspection
Do not assume the visible clothing is the active target. Always check this dropdown before painting or transferring.
#### Renderer
`Renderer` shows the active `SkinnedMeshRenderer`.
Use it to confirm that the tool is editing the correct renderer. This is especially important when a prefab has several skinned renderers with similar names.
You normally do not edit this field directly. It is an object reference display for safety and confirmation.
#### Mesh
`Mesh` shows the active renderer's `sharedMesh`.
Use it to confirm whether the renderer is still using the original mesh or a generated editable mesh. After importing weights, this should point to a generated skinning mesh asset.
If the wrong mesh is shown, stop and fix the selected target before painting.
#### Import Current Weights To Editable Mesh
Creates an editable generated mesh asset from the current mesh and assigns it to the active renderer.
Use it when:
* you want to preserve the current designer-authored weights before editing
* the target mesh is an imported FBX mesh
* the painting controls are disabled because the mesh is not editable
* you want a safe generated asset to receive weight and bindpose changes
Do not use it repeatedly as a normal save button. Repeated imports create additional generated mesh assets. Use `Save Mesh Asset` after the editable mesh exists.
#### Paint Bone
Selects the bone that receives weight when you paint.
Use it when:
* correcting a deformation around a specific joint
* shifting influence from one bone to another
* checking influence with `Overlay Mode = SelectedBone`
Avoid painting a bone just because it has the right name. Confirm the red bone guide is on the correct joint, especially after auto-rigging or replacing bones.
#### Paint In Scene
Enables Scene view brush painting.
Use it when you are ready to edit weights interactively.
Turn it off when:
* you only want to inspect overlays
* you are moving the camera a lot
* you are editing bones with transform handles
* you want to avoid accidental brush strokes
#### Show Weight Overlay
Draws a heat-map overlay on the current target mesh.
Use it to see where weights exist and how strong they are. The overlay is drawn on top of scene geometry, so it remains visible even when the painted surface would otherwise be hidden by the mesh depth buffer.
The overlay uses:
* blue for low influence
* green for medium influence
* red for high influence
If the overlay appears empty, possible causes are:
* the selected bone has no meaningful weight
* the mesh has no valid `boneWeights`
* the mesh is not readable
* the selected target is not the renderer you expected
* the overlay is showing `SelectedBone` and that bone is not used on visible vertices
Switch to `Overlay Mode = DominantInfluence` to confirm whether the mesh has any usable weights at all.
#### Overlay Mode
Controls which weights are shown by `Show Weight Overlay`.
| Mode | What It Shows | When To Use |
| ------------------- | ----------------------------------------------- | -------------------------------------------------------- |
| `SelectedBone` | Only the influence of the selected `Paint Bone` | Correcting a specific joint |
| `DominantInfluence` | The strongest influence on each vertex | Checking whether the mesh has normalized, usable weights |
Use `SelectedBone` for precise edits. Use `DominantInfluence` when diagnosing a mesh that looks unweighted or when checking for weakly weighted regions.
#### Brush Radius
Controls how far the weight brush reaches in world space.
Use a small radius for:
* fingers
* collars
* wrists
* cuffs
* face or neck areas
* tight folds near one joint
Use a larger radius for:
* torso clothing
* skirts
* large sleeves
* broad deformation cleanup
Avoid using a large radius near joints with very different motion, such as shoulder to chest, hip to pelvis, or elbow to lower arm. Large strokes can blur the boundary between bones and cause mushy deformation.
#### Brush Strength
Controls how much weight is added or removed per stroke.
Use low strength for:
* fine correction
* blending between nearby bones
* avoiding hard weight edges
Use high strength for:
* assigning rigid accessories
* fixing obviously wrong regions
* quickly blocking in a weight area before smoothing by hand
Do not use high strength across bend zones unless you intend to make a vertex follow one bone very strongly.
#### Symmetry
Mirrors weight painting across a local mesh axis.
| Mode | Behavior |
| ------------ | -------------------------- |
| `None` | Paint only under the brush |
| `Horizontal` | Mirror across local X |
| `Vertical` | Mirror across local Y |
Use symmetry for symmetrical clothing and body meshes.
Do not use symmetry when:
* the mesh is intentionally asymmetrical
* the mesh pivot or local axes are not centered as expected
* the left and right topology do not mirror cleanly
* one side has different bones or accessories
Horizontal symmetry also attempts to mirror left/right bone names, so painting a left arm bone can affect the matching right arm bone where a mirrored bone name is found.
#### Normalize Weights
Normalizes all weights on the current mesh.
Use it after:
* manual painting
* subtracting large areas
* removing bones
* creating new bones and redistributing weights
* importing or transferring from inconsistent sources
Unity `BoneWeight` stores up to four influences per vertex. Normalization keeps the strongest influences and scales them so the total is usable.
Do not use normalization as a substitute for checking deformation. It makes weights valid, but it does not guarantee that they are artistically correct.
#### Save Mesh Asset
Writes the current editable mesh asset to disk.
Use it after:
* weight painting
* normalization
* transfer operations
* bone removal
* bone creation
* bindpose changes
The tool also commits pending weight changes when you leave the tab, but explicit saves are safer during long authoring sessions.
If the UI shows `Weight changes are pending asset save`, click `Save Mesh Asset` before closing Unity or running a build.
### Body Weight Transfer
The `Body Weight Transfer` foldout contains tools that copy body skinning information to equipment.
These tools compare current world-space vertex positions. That means the preview alignment matters. If the equipment is offset, rotated incorrectly, or not in the same pose as the body, transferred weights will be wrong.
#### Auto-Rig Target To Character Bone Subset
Creates a character-bone subset for the selected equipment target and transfers body weights to that subset.
Use it for:
* shirts
* pants
* gloves
* boots
* armor pieces
* equipment that should deform like the body underneath it
This operation:
* finds nearest body vertices for the equipment vertices
* reads the body bone weights from those body vertices
* collects only the character bones that are actually used by the transferred weights
* assigns that smaller bone list to the equipment renderer
* remaps weights to the new subset
* rebuilds bindposes
* writes the generated mesh and prefab renderer changes
Do not use it blindly on:
* weapons
* rigid props
* wings
* capes with independent bones
* long skirts with custom skirt bones
* hair meshes
* equipment with special helper bones you want to keep
For those items, preserving source detail bones or using manual mapping is usually safer.
#### Transfer Body Weights To Selected Mesh
Transfers body weights to only the active `Target Mesh`.
Use it when:
* one equipment item needs correction
* you want to test the result on a single mesh before applying broadly
* the equipment already has a compatible bone list
This transfer remaps body weights onto the target renderer's existing bones by transform or name. It does not replace the renderer's bone list with a smaller character subset.
If the target renderer does not have matching bone names or shared character bone transforms, use `Auto-Rig Target To Character Bone Subset` instead.
#### Transfer Body Weights To All Loaded Equipment
Transfers body weights to every loaded equipment target, skipping the body mesh.
Use it when:
* several loaded clothing pieces are already aligned
* the equipment set belongs to the same body region
* you want a fast first pass for multiple garments
Avoid it when:
* some loaded equipment should remain rigid
* some equipment uses custom helper bones
* only one item is aligned correctly
* multiple items come from very different source rigs
For production, inspect each item after using this button. A transfer that is good for a shirt can be wrong for a cape, skirt, weapon, or accessory.
### Bone Editing
The `Bone Editing` foldout edits the active renderer's assigned skin bones.
#### Selected Bone
Chooses the bone currently edited by the numeric transform fields and scene handles.
This is separate from `Paint Bone` in the UI, but both use the same selected bone index in practice. If you switch targets, confirm the selected bone again.
#### Local Position
Edits the selected bone's local position relative to its parent.
Use it for:
* moving a newly created helper bone
* correcting small local rig offsets
* positioning an inserted bone between two existing joints
Do not use it casually on imported character bones unless you understand how that affects animation. Moving a real skeleton bone can change all child bones and any mesh weighted to them.
#### Local Rotation
Edits the selected bone's local rotation.
Use it for:
* orienting a new helper bone
* correcting an inserted bone's local direction
* matching a bone chain's expected local axis
Do not rotate source rig bones just to make the visual pylon look nicer. The transform affects skinning and animation.
#### Local Scale
Edits the selected bone's local scale.
Use it only when required.
Avoid non-uniform scale on normal deform bones. It can create deformation differences between editor preview, runtime, imported animation clips, and third-party systems such as cloth.
#### Select Bone
Selects the actual bone transform in Unity's hierarchy.
Use it when:
* you want to inspect the bone in the Inspector
* you need to see its hierarchy position
* you want to use Unity selection tools
#### Frame Bone
Frames the selected bone in the Scene view.
Use it when a bone is hidden inside a mesh, very small, or far from the current camera.
#### Remove Selected Bone From Skin
Removes the selected bone from the renderer's `bones` list and remaps any weights that referenced it.
Use it when:
* a skin bone is no longer needed
* a wrong helper bone was added
* a transfer or import left an unused bone in the renderer bone list
The removed bone's weights are assigned to a fallback bone, preferably a parent bone that is still in the skin, otherwise another remaining bone.
Important limitations:
* the last remaining skin bone cannot be removed
* this removes the bone from the skin list, not necessarily from the hierarchy
* prefab cleanup is conservative and avoids deleting transforms that may be referenced by other renderers or components
* deformation must be checked after removal because fallback remapping is safe but not always artistically correct
#### Replace Bones With Character Subset + Transfer Weights
Replaces the selected equipment renderer's skin bones with only the character body bones that are needed by transferred body weights.
This is similar to `Auto-Rig Target To Character Bone Subset`.
Use it when:
* an equipment prefab has an old rig that should be replaced
* the equipment should follow the character's skeleton directly
* you want to remove unnecessary leg, head, hand, or accessory bones from a garment that only covers the torso
The prefab-side operation creates a `__CharacterBoneSubset` hierarchy in the equipment prefab and removes old unreferenced prefab bone transforms when it is safe to do so.
Do not use it when the equipment needs its own special bones. If a dress has skirt bones, a cape has cape bones, hair has hair bones, or armor has custom mechanical bones, this operation may remove behavior you actually wanted.
### Create Bone
The `Create Bone` section adds a new transform and appends it to the active renderer's skin bone list.
#### Parent Bone
Selects the parent transform for the new bone.
Use it to choose where the new bone starts in the hierarchy.
Example:
* to create a `neck_02` bone between `neck_01` and `head`, set `Parent Bone = neck_01`
* to create a chest helper bone, set `Parent Bone = spine_03` or the closest equivalent
#### End Bone
Optionally selects an existing bone that should become the child of the new bone.
This is how you define a meaningful bone segment length.
Example:
* `Parent Bone = neck_01`
* `End Bone = head`
* `Name = neck_02`
The tool creates `neck_02` under `neck_01`, then reparents `head` under `neck_02` while preserving the head's world position and rotation.
Use `End Bone` when inserting a bone into an existing chain.
Use `None` when creating a leaf/helper bone that does not need to sit between two existing joints. A leaf bone has no true child segment, so the scene display draws a short pylon for visibility.
Invalid cases:
* `End Bone` cannot be the same as `Parent Bone`
* `End Bone` cannot be an ancestor of `Parent Bone`
#### Name
Sets the new bone GameObject name.
Use clear rig-style names, for example:
* `neck_02`
* `breast_l_helper`
* `skirt_front_01`
* `pauldron_r_helper`
Avoid generic names like `New_Bone` in final assets. Bone names matter for later mapping, debugging, and prefab maintenance.
#### Local Position
Sets the new bone's local position relative to `Parent Bone`.
Use this to place the new bone at the correct joint start.
When inserting between parent and end bones, start with a small offset along the chain, create the bone, then refine with the Move tool.
#### Local Rotation
Sets the new bone's local rotation.
Use it when the helper bone needs an initial orientation. If you are unsure, leave it at zero and rotate it after creation in Scene view.
#### Local Scale
Sets the new bone's local scale.
The safest default is `1, 1, 1`.
Avoid using scale as a substitute for bone length. In Unity, a bone segment is visually defined by the distance from a transform to its child or chosen end bone. The transform scale does not create a child endpoint by itself.
#### Create Bone And Add To Skin
Creates the bone, appends it to the renderer's skin bone list, creates a bindpose entry, and selects the new bone.
The new bone does not automatically receive meaningful weights. After creating it, paint weights, transfer weights, or normalize as needed.
### How Weight Painting Works
Each painted vertex stores up to four bone influences because Unity's `BoneWeight` type supports four influences.
When you paint a selected bone:
1. the selected bone's weight is increased or decreased
2. the remaining influences are scaled to keep the vertex usable
3. the strongest influences are kept
4. the result is normalized
This keeps the mesh valid, but it also means a very strong stroke can push out weaker secondary influences. Use lower strength for subtle blending.
### How Weight Transfer Works
Body weight transfer uses nearest world-space body vertices.
For each equipment vertex:
1. the tool bakes the current body mesh pose
2. the tool bakes the current target equipment mesh pose
3. the nearest body vertex is found
4. the body vertex's weights are copied
5. the copied bone indices are remapped to the target bone list or the generated character subset
This is why alignment is critical. The transfer is spatial, not semantic. If a shirt is rotated away from the torso, its vertices may pick weights from the wrong body region.
### Cross-Rig Notes
For cross-rig equipment, configure and preview the equipment first.
Before transferring or auto-rigging:
* confirm `Apply Bind Pose On Equip` is correct for the equipment
* confirm `Skip Runtime Root Alignment` is correct for the equipment
* use the Fit Sculptor orientation tools if the preview is rotated incorrectly
* confirm the equipment sits on the body in the same pose you intend to transfer from
The Skinning tab uses current baked world positions for overlay, painting collider, and transfer operations. If the Fit Sculptor preview is wrong, the skinning result will also be wrong.
### Addressables And Prefabs
When editing addressable equipment prefabs, remember:
* the edited prefab may reference generated mesh assets from `Generated/Skinning`
* those generated mesh assets must be available as project assets
* if the addressable prefab is moved or duplicated, verify the generated mesh reference
* if you rebuild DLL exports, generated authoring output should stay excluded from DLL source export
The Skinning module edits mesh and prefab data. It does not use the `EquipmentFitDataHolder` or `Equipment & Body Culling Data Holder` storage pattern because weights and bindposes belong to the mesh asset and renderer.
### Performance Notes
Weight painting and overlays are editor tools, but heavy meshes can still be expensive.
Cost increases with:
* high vertex count
* high triangle count
* multiple skinned renderers
* enabled heat-map overlay
* frequent bone transform changes
* large brush radius
* repeated transfer operations
The tool caches baked vertices, paint colliders, mirror maps, and overlay data where possible. Still, if the editor slows down:
* disable `Show Weight Overlay` while painting broad strokes
* paint one target mesh at a time
* use smaller brush radii for dense meshes
* save periodically instead of after every tiny adjustment
* avoid constantly changing bones while the overlay is enabled
* transfer to one selected mesh first before using all-loaded transfer
### What You Should Not Do
Avoid these workflows unless you have a specific reason:
* do not paint directly on an original imported FBX mesh
* do not repeatedly click `Import Current Weights To Editable Mesh` as a save workflow
* do not use all-loaded transfer when loaded equipment includes rigid props or custom bone chains
* do not replace an equipment rig with the character subset if the item needs independent helper bones
* do not use symmetry on asymmetrical meshes
* do not create many unnamed `New_Bone` transforms
* do not remove bones without checking deformation in animation
* do not rely on neutral-pose appearance only
* do not scale production skeleton bones casually
* do not delete generated skinning mesh assets that prefabs reference
### Troubleshooting
| Problem | Likely Cause | Fix |
| ------------------------------------------------ | ------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------ |
| `Skinning` tab is missing | Optional module DLL/source is not installed | Install the Skinning module under `Editor/Modules/Skinning` or include its editor DLL |
| Paint controls are disabled | Mesh is not editable or renderer has no bones | Click `Import Current Weights To Editable Mesh`; verify renderer bones |
| Weight overlay shows nothing | Selected bone has no weights, mesh has no weights, or wrong target is selected | Try `Overlay Mode = DominantInfluence`; confirm `Target Mesh`, `Renderer`, and `Mesh` |
| Overlay appears offset from mesh | Preview alignment, bindpose, or target renderer is wrong | Confirm cross-rig settings and reopen the sculptor after applying orientation changes |
| Paint brush appears but weights are hard to read | Overlay disabled or selected bone influence is low | Enable `Show Weight Overlay`; use `SelectedBone` or `DominantInfluence` appropriately |
| Bone dropdown does not show expected bones | The active renderer's `bones` list does not contain them | Select the correct target renderer or replace/assign the expected bone subset |
| Transfer gives wrong deformation | Equipment was not aligned to body during transfer | Fix Fit Sculptor alignment, then transfer again |
| Auto-rig removes useful helper bones | Character subset operation only keeps body bones used by transferred weights | Use manual transfer or preserve the source rig for items with custom helper bones |
| New bone looks like a tiny point | It has no child/end segment | Use `End Bone` when inserting into a chain, or move/rotate the leaf bone after creation |
| Removing a bone changes deformation too much | Weights were remapped to fallback bone | Repaint the affected area or undo and transfer again |
| Mirrored painting affects the wrong side | Mesh local axes or topology are not symmetrical | Set `Symmetry = None` and paint manually |
| Generated asset filename becomes long | Older generated mesh name was reused too many times | Current module strips repeated suffixes and caps generated names; delete obsolete generated assets if needed |
### Practical Examples
#### Preserve And Correct Designer Weights
Use this when an equipment item already deforms mostly correctly.
1. Select the equipment target.
2. Click `Import Current Weights To Editable Mesh`.
3. Enable `Show Weight Overlay`.
4. Choose the problematic `Paint Bone`.
5. Paint small corrections with low `Brush Strength`.
6. Click `Normalize Weights`.
7. Click `Save Mesh Asset`.
This is the safest workflow because it keeps the original weighting intent and only adjusts problem areas.
#### Auto-Rig A Shirt To The Character
Use this when a shirt should follow the character torso and arms.
1. Confirm the shirt is aligned in the Fit Sculptor preview.
2. Select the shirt in `Target Mesh`.
3. Click `Import Current Weights To Editable Mesh`.
4. Click `Auto-Rig Target To Character Bone Subset`.
5. Inspect shoulders, chest, spine, and upper arms with the overlay.
6. Paint corrections around armpits and collar.
7. Normalize and save.
8. Test walking, arm raise, crouch, and twist animations.
#### Insert A Bone Between Neck And Head
Use this when a chain needs an intermediate bone.
1. Set `Parent Bone = neck_01`.
2. Set `End Bone = head`.
3. Set `Name = neck_02`.
4. Set a starting local position, or leave it at zero and adjust after creation.
5. Click `Create Bone And Add To Skin`.
6. Move/rotate the new bone with Unity handles.
7. Paint or transfer weights to use the new bone.
8. Normalize and save.
### Related Docs
* Equipment Fit Sculptor
* EquipmentManager
* Cross-Rig Tools and Troubleshooting
* Body Culling and Mask Painter
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