readme edit

README.md

-# Node 3D Portrayal Service (extended) 
+# Node 3D Portrayal Service extended 
 
 ![](figures/home.jpg)
-This is a 3D Portrayal Service implementation that is compatible with [3D Tiles](https://github.com/CesiumGS/3d-tiles) and [i3s](https://github.com/Esri/i3s-spec) specifications.
+This is a 3D Portrayal Service implementation that is compatible with [3D Tiles](https://github.com/CesiumGS/3d-tiles) and [i3s](https://github.com/Esri/i3s-spec) specifications. In case of i3s it performs an active node selection.
 
 
 ## Installing