contour-demo-line-layer.js

const contourLayer = new FeatureLayer({
    url: "https://services2.arcgis.com/cFEFS0EWrhfDeVw9/arcgis/rest/services/ContourLinesZurichDemo/FeatureServer",
    elevationInfo: {
      mode: "absolute-height",
      featureExpressionInfo: {
        expression: "Pow($feature.elevation,1.2)"
      }
    },
    renderer: {
      type: "simple",
      symbol: {
        type: "line-3d",
        symbolLayers: [{
          type: "line",
          size: "1px",
          material: {
            color: [86, 72, 31]
          }
        }]
      },
      visualVariables: [{
        type: 'opacity',
        field: 'elevation',
        stops: [{
          value: 400,
          opacity: 0.3
        }, {
          value: 800,
          opacity: 0.9
        }]
      }]
    }
});
webscene.add(contourLayer);