openlayers 3 - How to extrude height ol3-Cesium? -

i've got geojson can load in ol3 without problems.

 var layer = new ol.layer.vector({    source: new ol.source.vector({       format: new ol.format.geojson(),       url: 'my_file.json',    })  }); 

my geojson have got properties (let's foo ) want use extrudedheight.

i've done in cesium (see cesium exemple): http://cesiumjs.org/cesium/apps/sandcastle/index.html?src=geojson%20and%20topojson.html&label=showcases

but can't find way on ol3 layer.

any clue ?

edit:

i've hacked bit , create featureconverter this:

test = {};   function extend(base, sub) {   // avoid instantiating base class setup inheritance   // see https://developer.mozilla.org/en-us/docs/web/javascript/reference/global_objects/object/create   // polyfill   // also, recursive merge of 2 prototypes, don't overwrite   // existing prototype, still maintain inheritance chain   // @ccnokes   var origproto = sub.prototype;   sub.prototype = object.create(base.prototype);   (var key in origproto)  {      sub.prototype[key] = origproto[key];   }   // remember constructor property set wrong, let's fix   sub.prototype.constructor = sub;   // in ecmascript5+ (all modern browsers), can make constructor property   // non-enumerable if define instead   object.defineproperty(sub.prototype, 'constructor', {     enumerable: false,     value: sub   }); }    test.featureconverter = function(scene) {   olcs.featureconverter.call(this, scene); }  test.featureconverter.prototype = {   olpolygongeometrytocesium : function(layer, feature, olgeometry, projection, olstyle) {      olgeometry = olcs.core.olgeometrycloneto4326(olgeometry, projection);     goog.asserts.assert(olgeometry.gettype() == 'polygon');      var rings = olgeometry.getlinearrings();     // update cesium externs before adding property     var hierarchy = {};     var polygonhierarchy = hierarchy;     goog.asserts.assert(rings.length > 0);      (var = 0; < rings.length; ++i) {       var olpos = rings[i].getcoordinates();       var positions = olcs.core.ol4326coordinatearraytocscartesians(olpos);       goog.asserts.assert(positions && positions.length > 0);       if (i == 0) {         hierarchy.positions = positions;       } else {         hierarchy.holes = {           // update cesium externs before adding property           positions: positions         };         hierarchy = hierarchy.holes;       }     }      var fillgeometry = new cesium.polygongeometry({       // update cesium externs before adding property       polygonhierarchy: polygonhierarchy,       perpositionheight: true,       extrudedheight: parseint(feature.getproperties()['foo'])     });      var outlinegeometry = new cesium.polygonoutlinegeometry({       // update cesium externs before adding property       polygonhierarchy: hierarchy,       perpositionheight: true     });      var primitives = this.wrapfillandoutlinegeometries(         layer, feature, olgeometry, fillgeometry, outlinegeometry, olstyle);      return this.addtextstyle(layer, feature, olgeometry, olstyle, primitives);   } }  extend(olcs.featureconverter, test.featureconverter); 

but not work... (and not know why...).