jtBaseApp/node_modules/cesium/Source/Scene/ModelInstance.js

import Matrix4 from "../Core/Matrix4.js";

/**
 * @private
 */
function ModelInstance(collection, modelMatrix, instanceId) {
  this.primitive = collection;
  this._modelMatrix = Matrix4.clone(modelMatrix);
  this._instanceId = instanceId;
}

Object.defineProperties(ModelInstance.prototype, {
  instanceId: {
    get: function () {
      return this._instanceId;
    },
  },
  model: {
    get: function () {
      return this.primitive._model;
    },
  },
  modelMatrix: {
    get: function () {
      return Matrix4.clone(this._modelMatrix);
    },
    set: function (value) {
      Matrix4.clone(value, this._modelMatrix);
      this.primitive.expandBoundingSphere(this._modelMatrix);
      this.primitive._dirty = true;
    },
  },
});
export default ModelInstance;