automatic-skinning-transfer.md

title	Automatic Skinning Transfer
description	Automatic Skinning Transfer can create deformation data for character accessories without manual skinning.

Automatic Skinning Transfer allows layered clothing and facial accessories to deform accurately along with the character model it's attached to without having to skin the accessory itself. Instead of the complex task of manually rigging and skinning models in 3D modeling software, you can use this feature to transfer or generate skinning data to the accessory. When using Automatic Skinning Transfer, the Roblox Engine creates and applies skinning at runtime.

No skinning of accessory geometry is required to use Automatic Skinning Transfer. In fact, auto-skinned accessories work well with most characters they're attached to, even if those characters have a different number of joints, bones, or use a different kind of skinning, and the accessories move accurately with characters as they animate.

Skinning is still an important concept for character creation, and if you're creating custom characters, you may want to apply skinning data to the model to create a character with more natural looking poses and animations. For information on how to skin a mesh, see Skin a humanoid model.

Because the skinning transfer process uses a character's outer cage to help calculate skinning data to apply onto the accessory, it's important that all [layered clothing requirements](../../art/accessories/project-files.md) are still met when creating accessories.

Enable Automatic Skinning Transfer

To enable the Automatic skinning transfer process, you must enable the Class.WrapLayer.AutoSkin|AutoSkin property within the Class.WrapLayer instance of the layered Class.Accessory you want to automatically skin, then set it to one of the following values:

• Disabled: Disables the Automatic Skinning Transfer process. This is the default value.
• EnabledOverride: Enables the Automatic Skinning Transfer process, and allows it to override any existing skinning information found on the accessory at runtime.
• EnabledPreserve: Enables the Automatic Skinning Transfer process, but doesn't allow it to override any existing skinning information found on the accessory at runtime. If there isn't any skinning to maintain, the Automatic Skinning Transfer process automatically creates new skinning data.

When there isn't any skinning data on the accessory, or if you choose to override any existing skinning data associated with the accessory, the Roblox Engine calculates skinning data from the character's geometry and cages, then the new skinning data and rig associated with the accessory drives the accessory's deformations and motions in sync with the source geometry itself.

Best practices

While Automatic Skinning Transfer often works better than manual skinning, there are some best practices to reduce unexpected behavior with the accessory skinning. Like all modeling processes, constantly test your layered clothing and facial accessories on different avatar types to achieve the results you want.

Special skinning transfer joints

Automatic skinning transfer may not work well for certain detailed accessory types, like eyelashes or eyebrows. To get a more controlled skinning transfer result, you have the option to skin accessory geometry to one of two specially named joints: RBX_Leader and RBX_Follower.

It's best to create these joints/bones directly beneath the Root joint in your hierarchy for simplicity and clarity. These joints/bones won't be detected as a part of your character model's R15 rig on import.

Any vertices skinned to RBX_Leader will undergo the same transfer process that exists today. However, any vertices skinned to RBX_Follower will actually transfer based on their nearest leader vertex. This allows for better results in situations like an eyelash where the tip of an eyelash strand would normally transfer to somewhere on the brow area, rather than follow the base of the eyelash strand when moving.

For eyelashes, good candidates for RBX_Leader are the ones that are intended to sit right on the eyelid of the character. The remaining vertices can be skinned to RBX_Follower.

Vertices of an eyelash assigned to a RBX_Leader bone vertex group.

Vertices of an eyelash assigned to a RBX_Follower bone vertex group.

For eyebrows, good candidates for RBX_Leader are vertices along the edges that span the browline.

Vertices of an eyebrow assigned to a RBX_Leader bone vertex group.

Vertices of an eyebrow assigned to a RBX_Follower bone vertex group.

In Blender, user the Object Data Properties > Vertex Groups to manage and view your vertex group assignments.

In Blender, vertex groups automatically created after you make a bone object. This allows you to quickly set vertices to a specific bone vertex group. Eyelashes without transfer joints. Notice how the upper eyelashes near the bridge of the nose doesn't follow the eyelids as expected. Eyelashes with transfer joints. All eyelashes follow the leading vertices closest to the eyes.

No additional work is needed in Studio to support this method. If your accessory is set to Class.WrapLayer.AutoSkin.EnabledOverride and these joints exist with vertices assigned to them, then this skinning transfer variation will be in effect.

If you wish to upload an accessory using these joints as a UGC item, there are a few rules to be aware of:

• Vertices cannot be partially weighted to these joints. If you want to use them you must skin the vertex to the joint with a weight of 1.0.
• If these joints are present in the mesh, then the accessory must be set to WrapLayerAutoSkin.EnabledOverride.
• Body part meshes containing these joints will be rejected by validation.

Modify character cages

You can't upload assets with a partial cage to the Marketplace. You may use partial cages for assets intended for in-experience use, but the Marketplace validation process will reject assets with partial cages.

You can modify character cages for the accessories to deform accurately to the expected character surfaces using the Automatic Skinning Transfer. For example, auto-skinning may cause layered clothing to deform based on an incorrect body part because the transfer process is based on the closest distance between the accessory and its inner cage. In the following instance, a beard accessory was modeled using a blocky-type full-body cage. This causes the beard to deform incorrectly because parts of the beard are closer to the character cage's upper chest instead of the chin:

To prevent a layered accessory from using skinning data from an undesired area of the character's geometry, you can model your asset on a different character mannequin cage. For example, a blocky-type character will struggle with a beard skinning to the torso, but a character with an actual neck, like a humanoid, won't have this problem.

Alternatively, you can remove parts of the outer cage that the layered accessory shouldn't be skinned to. This is not a valid workflow for assets intended for the Marketplace, but you can use this for in-experience assets or assets for other use. For example, the following image shows how the outer cage was modified so that it only includes the head geometry. With this improvement to the outer cage, when you automatically transfer skinning data, the beard and partial cage now correctly transfer skinning only from the head geometry.

It's important to note that you could also solve the previous example's deformation issue by using a different cage altogether. For example, if you use a more humanoid cage with more space between the chest and the chin, the beard is closest to the head instead of being near the chest or neck area, so the Automatic Skinning Transfer wouldn't transfer skinning data from those regions.

By modifying different regions of the character's cage, you can ensure that your layered clothing and facial accessories deform in relation to the correct region of the body or head, such as modifying the character model's arms so dresses don't incorrectly attach to them while a character is running, or modifying pants that incorrectly map to feet. The following video demonstrates how a jacket's collar incorrectly moves with the head, as the layered clothing is deforming in the collar region, which is closest to the head portion of the cage. To resolve this, you can remove the head portion of the cage so that the jacket won't incorrectly deform in relation to the head at all. Instead, it will deform in relation to the shoulder region, which is much more appropriate for this article of clothing.

During the asset creation process, it's important to verify what skinning solution works best for your design by testing your individual assets on multiple models and animations. You can always skin your assets manually and choose to use the Automatic Skinning Transfer later.

Different accessory categories

Automatic skinning transfer may not work well for certain accessory categories, such as hat, and glasses-type accessories. For example, hat or glasses accessories might introduce deformation in areas that should typically be rigid. In general, those accessories should remain rigid, and you shouldn't associate any skinning data with them.

For a summary of suggested Class.WrapLayer.AutoSkin parameters for different accessory categories, see the following table:

Accessory Category	Suggested Parameter
Beard	`EnabledOverride`
Eyebrow	`EnabledOverride`
Eyelash	`EnabledOverride`
Hair	`Disabled`
Hat	`Disabled`
Glasses	`Disabled`
Shirt	`EnabledOverride` or `EnabledPreserve`
Pants	`EnabledOverride` or `EnabledPreserve`
Shoes	`EnabledOverride` or `EnabledPreserve`