computeBoundingSphere() {

		if ( this.boundingSphere === null ) {

			this.boundingSphere = new Sphere();

		}

		const boundingSphere = this.boundingSphere;
		const instanceInfo = this._instanceInfo;

		boundingSphere.makeEmpty();
		for ( let i = 0, l = instanceInfo.length; i < l; i ++ ) {

			if ( instanceInfo[ i ].active === false ) continue;

			const geometryId = instanceInfo[ i ].geometryIndex;
			this.getMatrixAt( i, _matrix$1 );
			this.getBoundingSphereAt( geometryId, _sphere$2 ).applyMatrix4( _matrix$1 );
			boundingSphere.union( _sphere$2 );

		}

	}
Computes the bounding sphere, updating {@link BatchedMesh#boundingSphere}.
Bounding spheres aren't computed by default. They need to be explicitly computed,
otherwise they are `null`.