如何在运行时修改地形的比例？

参照 arcgis js sdk 中的 Custom ElevationLayer - Exaggerating elevation 例子， 用 TypeScript 实现了一个  ExaggeratedElevationLayer ， 可以根据 exaggeration 属性来设置地形缩放的比例， 代码如下：

import {

    subclass, declared, property

} from "esri/core/accessorSupport/decorators";

import BaseElevationLayer = require('esri/layers/BaseElevationLayer');

import ElevationLayer = require('esri/layers/ElevationLayer');



@subclass('beginor.ExaggeratedElevationLayer')

class ExaggeratedElevationLayer extends(declared(BaseElevationLayer)) {



    @property()

    public exaggeration: number;

    @property()

    public url: string;

    @property()

    public get type(): string { return 'exaggerated-elevation'; }



    private elevation: ElevationLayer;



    constructor(properties: ExaggeratedElevationLayerProperties) {

        super(properties);

        if (!this.exaggeration) {

            this.exaggeration = 1.0;

        }

    }



    public load(signal: AbortSignal): IPromise<any> {

        this.elevation = new ElevationLayer({

            url: this.url

        });

        return this.addResolvingPromise(this.elevation.load(signal));

    }



    fetchTile(

        level: number,

        row: number,

        column: number,

        options: __esri.ElevationLayerFetchTileOptions

    ): IPromise<__esri.ElevationTileData> {

        return this.elevation.fetchTile(level, row, column, options).then(

            data => {

                const exag = this.exaggeration;

                for (let i = 0; i < data.values.length; i++) {

                    data.values[i] = data.values[i] * exag;

                }

                return data;

            }

        );

    }



}



interface ExaggeratedElevationLayerProperties extends __esri.BaseElevationLayerProperties {

    url: string;

    exaggeration?: number;

}



export = ExaggeratedElevationLayer;

在项目中使用它的代码如下：

import WebScene = require('esri/Map');

import SceneView = require('esri/views/SceneView');

import externalRenderers = require('esri/views/3d/externalRenderers');



import ExaggeratedElevationLayer = require('beginor/ExaggeratedElevationLayer');



const map = new WebScene({

    basemap: 'streets',

    ground: {

        layers: [

            new ExaggeratedElevationLayer({

                url: 'http://elevation3d.arcgis.com/arcgis/rest/services/WorldElevation3D/Terrain3D/ImageServer',

                exaggeration: 5

            })

        ]

    }

});



const view = new SceneView({

    map: map,

    container: 'viewDiv',

    center: [113.2, 23.4],

    zoom: 13,

    camera: {

        position: {

            spatialReference: { wkid: 102100 },

            x: 12601020.732296046,

            y: 2661706.7320940713,

            z: 10515.040601080284

        },

        heading: 0,

        tilt: 60

    }

});

现在， 需要在运行时修改地形的缩放比例， 通过从当前场景中找到这个地形图层， 修改 exaggeration 属性， 并没有效果。 我找到的唯一方法是将地形图层删掉再重新添加到场景中， 示例代码如下：

var btnTgl = document.getElementById('eleTgl') as HTMLButtonElement;

btnTgl.addEventListener('click', e => {

    const ground = view.map.ground;

    var eleLayer = ground.layers.getItemAt(0);

    ground.layers.remove(eleLayer);

    let exLayer = eleLayer as any as ExaggeratedElevationLayer;

    if (exLayer.exaggeration == 5) {

        exLayer = new ExaggeratedElevationLayer({

            exaggeration: 1,

            url: exLayer.url

        });

    }

    else {

        exLayer = new ExaggeratedElevationLayer({

            exaggeration: 5,

            url: exLayer.url

        });

    }

    ground.layers.add(exLayer as any);

});

这个方法虽然可行，但是用户体验比较差， 需要重新构建地形，而且还需要重新下载大量的高程数据。  所以，请问有没有什么更加高效的方法可以修改地形的缩放比例呢， 比如如何触发地形图层的重新渲染，而不是重新构建地形？