model size at distance does not animate smoothly


I am animating a model moving away from the camera, but there is a noticeable effect of the scaling of the model becoming less and less smooth the further away it moves. it's as if its dimensions snap to the nearest pixel. — example video:

is there any way to fix or avoid this?

(I'm on HEAD of the 3d-tiles branch,) and this is the relevant code:

const TWEEN = require('tween.js');
const modelEntity = viewer.entities.add({
  position: Cesium.Cartesian3.fromDegrees(/* ... */),
  model: { uri: constants.modelUrl }
const startPos = modelEntity.position._value.clone();
const carto = Cesium.Cartographic.fromCartesian(startPos);
const groundPos = Cesium.Cartesian3.fromRadians(
  () => { TWEEN.update(); }
const aniDuration = 5000;
const tween = new TWEEN.Tween(startPos)
  .to(R.pick(['x', 'y', 'z'], groundPos), aniDuration)
  .onUpdate(function() {
    // console.log(this.x, this.y, this.z);
    modelEntity.position = this;

It’s not really possible to avoid this currently unless Cesium were to have a more involved antialising pipeline (maybe in the future with MSAA / WebGL2).