施力后ARKit获取节点位置

how to track the position of a node after applying force in Arkit 1.5

我有一个节点(SCNSphere),我在其中应用了force。节点具有 dynamic SCNNode 使用 physicsBody?.applyForce 一切都很好

问题是在使用武力之后 动态 身体在不断下降 我要追踪那个位置

renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) 我打印 position 属于 SCN节点 但它每次都显示相同的位置,为什么Y位置不减少,因为它是向下的?

就像

<SCNNode: 0x280f29500 'ball' pos(-0.165368 0.3 -0.809096) | geometry=<SCNSphere: 0x280619380 | radius=0.150> | no child> <SCNNode: 0x280f29500 'ball' pos(-0.165368 0.2 -0.809096) | geometry=<SCNSphere: 0x280619380 | radius=0.150> | no child> <SCNNode: 0x280f29500 'ball' pos(-0.165368 0.1 -0.809096) | geometry=<SCNSphere: 0x280619380 | radius=0.150> | no child>

如何添加节点

        let ballWithOrientation = getNewBallNode() // return ball node + position
        let ballNode = ballWithOrientation.ball // it is the SCNNode
        self.sceneView.scene.rootNode.addChildNode(ballNode ?? SCNNode()) // Added to the scene 
        let cameraPosition =  self.sceneView.pointOfView?.worldFront

        let target =  SCNVector3(Double(cameraPosition?.x ?? 1) * forceVector,Double (cameraPosition?.y  ?? 1) * forceVector,Double(cameraPosition?.z ?? 1) * forceVector) // Vector of direction 
        let throwSpeed = self.calculateBestThrowSpeed(origin: ballNode!.position, target:target , timeToTarget: 0.66)  Calculated vector with velocity 
        ballNode?.physicsBody?.applyForce(throwSpeed, asImpulse: true) // apply force 

问题 施力后如何跟踪SCNNode的世界位置?