code: function (idx) {
  
          var polygons = this._triangulationResults[idx - this._startIndex];
  
          var sideVertexCount = 0;
          var sideTriangleCount = 0;
  
          for (var i = 0; i < polygons.length; i++) {
              sideVertexCount += polygons[i].points.length / 3;
              sideTriangleCount += polygons[i].indices.length / 3;
          }
  
          var vertexCount = sideVertexCount * 2 + sideVertexCount * 4;
          var triangleCount = sideTriangleCount * 2 + sideVertexCount * 2;
  
          return {
              vertexCount: vertexCount,
              triangleCount: triangleCount
          };
      }
docs: Get region vertex and triangle count