Chapter 13: SkinnedMesh

Core Idea

A mesh that has a Skeleton that can then be used to animate the vertices of the geometry with skinning/skeleton animation.

Next to a valid skeleton, the skinned mesh requires skin indices and weights as buffer attributes in its geometry. These attribute define which bones affect a single vertex to a certain extend.

Typically skinned meshes are not created manually but loaders like GLTFLoader or FBXLoader import respective models.

Key Concepts

• bindMatrix : Matrix4: The base matrix that is used for the bound bone transforms.
• bindMatrixInverse : Matrix4: The base matrix that is used for resetting the bound bone transforms.
• bindMode : AttachedBindMode | DetachedBindMode: AttachedBindMode means the skinned mesh shares the same world space as the skeleton. This is not true when using DetachedBindMode which…
• boundingBox : Box3: The bounding box of the skinned mesh. Can be computed via SkinnedMesh#computeBoundingBox.
• boundingSphere : Sphere: The bounding sphere of the skinned mesh. Can be computed via SkinnedMesh#computeBoundingSphere.
• isSkinnedMesh : boolean (readonly): This flag can be used for type testing.

Reference Tables

Constructor

Signature
`new SkinnedMesh( geometry : BufferGeometry, material : Material

Properties

Property	Description
.bindMatrix : Matrix4	The base matrix that is used for the bound bone transforms.
.bindMatrixInverse : Matrix4	The base matrix that is used for resetting the bound bone transforms.
`.bindMode : AttachedBindMode	DetachedBindMode`
.boundingBox : Box3	The bounding box of the skinned mesh. Can be computed via SkinnedMesh#computeBoundingBox.
.boundingSphere : Sphere	The bounding sphere of the skinned mesh. Can be computed via SkinnedMesh#computeBoundingSphere.
.isSkinnedMesh : boolean (readonly)	This flag can be used for type testing.

Methods

Method	Description
`.applyBoneTransform( index : number, target : Vector3	Vector4 ) : Vector3
.bind( skeleton : Skeleton, bindMatrix : Matrix4 )	Binds the given skeleton to the skinned mesh.
.computeBoundingBox()	Computes the bounding box of the skinned mesh, and updates SkinnedMesh#boundingBox. The bounding box is not automatically computed by the engine; this method must be c…
.computeBoundingSphere()	Computes the bounding sphere of the skinned mesh, and updates SkinnedMesh#boundingSphere. The bounding sphere is automatically computed by the engine once when it i…
.normalizeSkinWeights()	Normalizes the skin weights which are defined as a buffer attribute in the skinned mesh's geometry.
.pose()	This method sets the skinned mesh in the rest pose).

Key Takeaways

1. SkinnedMesh extends: EventDispatcher → Object3D → Mesh
2. Most relevant properties: bindMatrix, bindMatrixInverse, bindMode, boundingBox.
3. Key methods: applyBoneTransform, bind, computeBoundingBox, computeBoundingSphere.

Connects To

• EventDispatcher: parent class
• Object3D: parent class
• Mesh: parent class
• Source: src/objects/SkinnedMesh.js