To help users that are building Cesium applications that need to run on closed networks (with no internet access), I’ve created a wiki page listing all parts of Cesium that contact the internet by default, and how to configure an application to avoid that. We’ll keep this up to date as we add any other online features that are activated by default.
https://github.com/AnalyticalGraphicsInc/cesium/wiki/Offline-Guide
Is there any offline method to calculate routes within cesium? (ex: calculate the driving distance between point A and point B)
If you mean client-side javascript only; no. If you are talking about a local server or desktop app that is not connected to the internet; it’s possible but I’ve never personally done it. You might want to check out OsmSharp, https://github.com/OsmSharp/OsmSharp. I’ve only used it for a couple of pet projects; but you can load it up with data from OpenStreetMaps (which provides a single large download of their entire dataset) and then use it for routing and all kinds of other calculations. One potential drawback (depending on who you ask) is that OsmSharp is GPL; so if you are releasing your app publicly; whichever piece uses it would have to be GPL too.