Earth coordinate of a point in the point cloud (gltf model) which is loaded on Cesium

I have a point cloud. I load it on Cesium by converting to a GLTF file. The model loading script is as below.

GpsX and GpsY corresponds to the origin [0,0,0] in the original point cloud.

My problem is to know the GpsX2 and GpsY2 for another point in the cloud which has [x2,y2,z2] values in the original point cloud.

Would you have advice to achieve earth coordinates of other points in the point cloud after they are loaded?

// Loading the point cloud as GLTF model:
roomModelGpsX = GpsX;
roomModelGpsY = GpsY;
roomModelHeight = firstFloorHeight;
roomModelPosition = Cesium.Cartesian3.fromDegrees(roomModelGpsY, roomModelGpsX, roomModelHeight);
headingAngle = Cesium.Math.toRadians(0);
roomModelPitch = 0;
roomModelRoll = 0;

hpr = new Cesium.HeadingPitchRoll(headingAngle, roomModelPitch, roomModelRoll);
orientation = Cesium.Transforms.headingPitchRollQuaternion(roomModelPosition, hpr);
roomModel = viewer.entities.add({
  name: 'room model',
  position: new Cesium.Cartesian3.fromDegrees(roomModelGpsY[i], roomModelGpsX[i], roomModelHeight[i]),
  orientation: orientation,
  model: {
    uri: roomModelUrl,
    scale: 1
  allowPicking: true

It isn’t possible to retrieve individual point positions using the Model api. You would need to load the gltf as JSON and parse the data yourself.