JavaScript ArcGIS BaseElevationLayer用法及代碼示例

AMD: require(["esri/layers/BaseElevationLayer"], (BaseElevationLayer) => { /* code goes here */ });

ESM: import BaseElevationLayer from "@arcgis/core/layers/BaseElevationLayer";

類： esri/layers/BaseElevationLayer

繼承: BaseElevationLayer > Layer > Accessor

自從：用於 JavaScript 4.4 的 ArcGIS API

BaseElevationLayer 旨在擴展以創建自定義高程圖層。您可以通過在 BaseElevationLayer 上調用 createSubclass() 來創建自定義 ElevationLayer。

如果新層需要獲取和準備資源，您可以在加載層之前異步初始化屬性。這是在 load() 方法中處理的。當圖層即將顯示時，此方法將由您或視圖調用一次。在方法主體中，您可以調用addResolvingPromise()來添加一個承諾，該承諾必須在該層被視為已加載之前解決。

您必須覆蓋 fetchTile() 方法中的邏輯才能返回自定義高程數據的值。這樣做可以誇大實際高程值或將專題數據映射為高程圖層。轉換高程數據值時，建議保持無數據值不變。

const ExaggeratedElevationLayer = BaseElevationLayer.createSubclass({
  load: function() {
    // add loadable dependencies here and include
    // their returned promises in the
    // addResolvingPromise() method
    this._elevation = new ElevationLayer({
      url: "//elevation3d.arcgis.com/arcgis/rest/services/WorldElevation3D/Terrain3D/ImageServer"
    });
    this.addResolvingPromise(this._elevation.load());
  },

  fetchTile: function(level, row, col, options) {
    // must resolve to an object with the following properties:
    // values <number[]>: an array of elevation values for each pixel
    // width <number>: the width of the tile in pixels
    // height <number>: the height of the tile in pixels
    // noDataValue <number>: value of pixels where no elevation data is present
    return this._elevation.fetchTile(level, row, col, options).then(function(data) {
      let exaggeration = this.exaggeration;
      // `data` is an object that contains the width of the tile in pixels,
      // the height of the tile in pixels, and the values of each pixel
      for (let i = 0; i < data.values.length; i++) {
         // each value represents an elevation sample for the
         // given pixel position in the tile
         // check if the value is a no data value
         if (data.values[i] !== data.noDataValue) {
           // multiply the elevation value by the exaggeration value
           data.values[i] *= exaggeration;
         }
      }
      return data;
    }.bind(this))
  }
});

創建圖層後，您必須將其添加到 Map.ground 屬性的圖層，並將Map添加到 SceneView 實例。

let map = new Map({
  basemap: "satellite",
  ground: {
    layers: [ new ExaggeratedElevationLayer() ]
  }
});
sceneView.map = map;