face);
        var feature = new ol.Feature({
          geometry: new ol.geom.Polygon(coordinates),
          face: face
        });
        feature.setId(face.id);
        faces.addFeature(feature);
      }

      function createNode(topo, coord) {
        var node;
        var existingEdge = topo.getEdgeByPoint(coord, 5)[0];
        if (existingEdge) {
          node = topo.modEdgeSplit(existingEdge, coord);
        } else {
          node = topo.addIsoNode(coord);
        }
        return node;
      }

