ol3_cesium my polygon float

Hello,
i need your kindle help please.
i’m trying to build a webmap using ol3-cesium libraries , when I switch 2d map to 3d map my polygon (geojson or geoserver wms, wfs) are not draped on stk-terrain but they are under the ground.
I tried to use geometry data both in EPSG 3857 that in EPSG 4326, but my polygons still remain under the ground.
I tried to load my polygon (wms and geojson) on the ol3-cesium example
http://openlayers.org/ol3-cesium/examples/epsg-4326.html
on 2d map they are correctly located but when I switch to 3d map the geometries disappear.
Unfortunately, I cannot understand why, if it is only a coordinates problem.
I think I know openlayer use EPSG 3857 and automatically projects the geometries to EPSG 4326, so it makes no difference to have the data in EPSG 3857 or EPSG 4326 , for cesium libraries it’s the same?
Thank you.

This is an excerpt of my code:

  _myStroke_ghiacciai = new ol.style.Stroke({
         color : 'rgba(0,0,255,1.0)',
         width : 0.8
      });

      _myFill_ghiacciai = new ol.style.Fill({
         color: 'rgba(0,0,255,0.2)'
      });
      
      myStyle_ghiacciai = new ol.style.Style({
         stroke : _myStroke_ghiacciai ,
         fill : _myFill_ghiacciai
       });
var ghiacciai = new ol.layer.Vector({
                  title: 'Ghiacciai',
                  visible: true,
                  source: new ol.source.Vector({
                  url: 'data/ghiacciai.json',
                  projection: 'EPSG:3857',
                  format: new ol.format.GeoJSON()
                      }) ,
                      style: myStyle_ghiacciai });

view = new ol.View({
     projection: ‘EPSG:3857’,
     center: ol.proj.transform([9.5, 46.1], ‘EPSG:4326’, ‘EPSG:3857’),
      zoom: 8,
      maxZoom: 14,
      minZoom: 7
      zoomFactor: 2
      });
  var map = new ol.Map({
    target: ‘map’,
    controls: ol.control.defaults().extend([
      new ol.control.ScaleLine(),
      new ol.control.ZoomSlider(),
]),
    renderer: ‘canvas’,
     layers: [
            new ol.layer.Group({
                ‘title’: ‘Base maps’
                layers: [
        
        new ol.layer.Tile({ title: ‘Ortofoto con strade’,
                type: ‘base’,
                visible: false,
                source: new ol.source.XYZ({
                  url: ‘http://api.tiles.mapbox.com/v4/digitalglobe.nmmigejm/{z}/{x}/{y}.png?access_token=pk.eyJ1IjoiZGlnaXRhbGdsb2JlIiwiYSI6ImNpZnB2bWUzNDZoczlzaWtxMmd2bDc3ZHQifQ.AHiF6mR5aXL0rdI4eLz2dA’, // You will need to replace the ‘access_token’ and ‘Map ID’ values with your own. http://developer.digitalglobe.com/docs/maps-api
        attribution: “© DigitalGlobe, Inc”
                })
        }),
        
        new ol.layer.Tile({
                        title: ‘Ortofoto’,
                        type: ‘base’,
                        visible: false,
                        source: new ol.source.XYZ({
                  attributions: [
                  new ol.Attribution({
                      html: ‘Tiles &copy; <a href="http://services.arcgisonline.com/ArcGIS/’ +
                      ‘rest/services/World_Topo_Map/MapServer">ArcGIS</a>’
                          })
                  ],
                  url: ‘http://server.arcgisonline.com/ArcGIS/rest/services/’ +
                  ‘World_Imagery/MapServer/tile/{z}/{y}/{x}’
                        })
                    }),
          new ol.layer.Tile({
                        title: ‘Topografica’,
            
                        type: ‘base’,
                        visible: true,
                        source: new ol.source.XYZ({
                  attributions: [
                  new ol.Attribution({
                      html: ‘Tiles &copy; <a href="http://services.arcgisonline.com/ArcGIS/’ +
                      ‘rest/services/World_Topo_Map/MapServer">ArcGIS</a>’ })],url: ‘http://server.arcgisonline.com/ArcGIS/rest/services/’ +‘World_Topo_Map/MapServer/tile/{z}/{y}/{x}’})
                    }),
                new ol.layer.Tile({
                        title: ‘Stradario’,
                        type: ‘base’,
                        visible: false,
                        source: new ol.source.XYZ({
  attributions: [new ol.Attribution({
html: ‘Tiles &copy; <a href="http://services.arcgisonline.com/ArcGIS/’ +
                  ‘rest/services/World_Topo_Map/MapServer">ArcGIS</a>’ } ],
url: ‘http://server.arcgisonline.com/ArcGIS/rest/services/’ +
‘World_Street_Map/MapServer/tile/{z}/{y}/{x}’ })})
                ] }),
            new ol.layer.Group({
                title: ‘Overlays’,
                layers: [ghiacciai ] }) ],
    view: view });

  var layerSwitcher = new ol.control.LayerSwitcher({
   tipLabel: 'Legenda'
   });
  map.addControl(layerSwitcher);
var zoomToExtentControl = new ol.control.ZoomToExtent({
    label: 'Home',
    extent:[1007934.024, 5888053.048, 1190159.773, 5768785.981],
    target: document.getElementById('home')
    });
    map.addControl(zoomToExtentControl);

  var ol3d = new olcs.OLCesium({map: map});
                    
  var scene = ol3d.getCesiumScene();
  var terrainProvider = new Cesium.CesiumTerrainProvider({
    url : '//assets.agi.com/stk-terrain/world',
    requestWaterMask : true,
    requestVertexNormals : false
  });
  scene.terrainProvider = terrainProvider;
  ol3d.setEnabled(false);

Hello,

my polygon (geojson or geoserver wms, wfs) are not draped on stk-terrain

OL3-Cesium reprojects automatically you vector data so it should appear on terrain

if you set the ‘altitudeMode’ to ‘clampToGround’.
See https://github.com/openlayers/ol3-cesium/blob/master/examples/vectors.js#L12

Raster layers (WMS) are automatically drapped on terrain by Cesium. Are you sure they are drawn?

You may want to check https://github.com/openlayers/ol3-cesium/issues/362.

Cheers,

Guillaume