text: var ol2d = new ol.Map({
    layers: [
      new ol.layer.Tile({
        source: new ol.source.OSM()
      })
    ],
    controls: ol.control.defaults({
      attributionOptions: /** @type {olx.control.AttributionOptions} */ ({
        collapsible: false
      })
    }),
    target: 'map',
    view: new ol.View({
      center: ol.proj.transform([25, 20], 'EPSG:4326', 'EPSG:3857'),
      zoom: 3
    })
  });
  
  var ol3d = new olcs.OLCesium(ol2d);
  var scene = ol3d.getCesiumScene();
  var terrainProvider = new Cesium.CesiumTerrainProvider({
      url : '//cesiumjs.org/stk-terrain/tilesets/world/tiles'
  });
  scene.terrainProvider = terrainProvider;
  
  