自定义 ElevationLayer - 作为高程的专题数据

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const Temperature3DLayer = BaseElevationLayer.createSubclass({
  properties: {
    // exaggerates the temps by 80000x so we can see
    // variation at large scales
    exaggeration: 80000
  },

  load: function() {
    // load ImageryLayer containing temperature values
    // See the code in the sandbox for details about
    // createTemperatureLayer()
    this._temperature = createTemperatureLayer(depth, tempDate, "lerc");
    this.addResolvingPromise(this._temperature.load());
  }
});

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fetchTile: function(level, row, col, options) {
  const bounds = this.getTileBounds(level, row, col);
  // Add one because of overlapping vertices in neighboring tiles
  const tileSize = this.tileInfo.size[0] + 1;
  const extent = new Extent({
    xmin: bounds[0],
    ymin: bounds[1],
    xmax: bounds[2],
    ymax: bounds[3],
    spatialReference: this.spatialReference
  });
  const factor = this.factor;

  // fetch the image representing temperature for the extent of the tile.
  // this method returns the pixel data of the image for the extent
  // of the given elevation tile
  return this._temperature.fetchImage(extent, tileSize, tileSize, options)
    .then((data) => {

      const pixelBlock = data.pixelData.pixelBlock;
      // contains the temperature values of each pixel in the image
      const elevations = pixelBlock.pixels[0];
      const stats = pixelBlock.statistics[0];
      // pixels that don't contain any temperature values
      const noDataValue = stats.noDataValue;

      elevations.forEach((value, index, pixelData) => {
        if (value !== noDataValue) {
          // multiply temperatures by the given factor
          pixelData[index] = value * factor;
        }
        else {
          // areas with no temperature data (land)
          // will be assigned the average sea surface
          // temperature (17 degrees Celsius)
          pixelData[index] = 17*factor;
        }
      });

      // return the modified temperatures as elevations
      return {
        values: elevations,
        width: pixelBlock.width,
        height: pixelBlock.height,
        noDataValue: noDataValue
      };
    });
}

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// Add the Temperature3DLayer as an elevation layer to the map
// with a 2D ImageryLayer representing elevation draped on top
const map = new Map({
  basemap: "oceans",
  ground: {
    layers: [new Temperature3DLayer()]
  },
  layers: [new Temperature2DLayer()]
});