_getHandJoint( hand, inputjoint ) {

		if ( hand.joints[ inputjoint.jointName ] === undefined ) {

			const joint = new Group();
			joint.matrixAutoUpdate = false;
			joint.visible = false;
			hand.joints[ inputjoint.jointName ] = joint;

			hand.add( joint );

		}

		return hand.joints[ inputjoint.jointName ];

	}
Returns a group representing the hand joint for the given input joint.

@private
@param {Group} hand - The group representing the hand space.
@param {XRJointSpace} inputjoint - The hand joint data.
@return {Group} A group representing the hand joint for the given input joint.