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

Question

I've got a GeoJson that I can load in ol3 without any 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 a properties (let's say foo ) that I want to use to extrudedHeight.
I've done this in Cesium (see the Cesium exemple): http://cesiumjs.org/Cesium/Apps/Sandcastle/index.html?src=GeoJSON%20and%20TopoJSON.html&label=Showcases
But I can't find a way to do this on my ol3 layer.
Any clue ?
Edit:
I've hacked a bit and create my FeatureConverter like this:
test = {};
function extend(base, sub) {
// Avoid instantiating the base class just to setup inheritance
// See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/create
// for a polyfill
// Also, do a recursive merge of two prototypes, so we don't overwrite
// the existing prototype, but still maintain the inheritance chain
// Thanks to #ccnokes
var origProto = sub.prototype;
sub.prototype = Object.create(base.prototype);
for (var key in origProto) {
sub.prototype[key] = origProto[key];
}
// Remember the constructor property was set wrong, let's fix it
sub.prototype.constructor = sub;
// In ECMAScript5+ (all modern browsers), you can make the constructor property
// non-enumerable if you define it like this 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();
// always update Cesium externs before adding a property
var hierarchy = {};
var polygonHierarchy = hierarchy;
goog.asserts.assert(rings.length > 0);
for (var i = 0; i < 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 = {
// always update Cesium externs before adding a property
positions: positions
};
hierarchy = hierarchy.holes;
}
}
var fillGeometry = new Cesium.PolygonGeometry({
// always update Cesium externs before adding a property
polygonHierarchy: polygonHierarchy,
perPositionHeight: true,
extrudedHeight: parseInt(feature.getProperties()['foo'])
});
var outlineGeometry = new Cesium.PolygonOutlineGeometry({
// always update Cesium externs before adding a 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 it does not work... (and I do not know why...).