init() {

		const bones = this.bones;
		const boneInverses = this.boneInverses;

		this.boneMatrices = new Float32Array( bones.length * 16 );

		// calculate inverse bone matrices if necessary

		if ( boneInverses.length === 0 ) {

			this.calculateInverses();

		} else {

			// handle special case

			if ( bones.length !== boneInverses.length ) {

				console.warn( 'THREE.Skeleton: Number of inverse bone matrices does not match amount of bones.' );

				this.boneInverses = [];

				for ( let i = 0, il = this.bones.length; i < il; i ++ ) {

					this.boneInverses.push( new Matrix4() );

				}

			}

		}

	}
Initializes the skeleton. This method gets automatically called by the constructor
but depending on how the skeleton is created it might be necessary to call this method
manually.