title: CesiumJS - How can I control viewer time and ticks?
body: <p>What I'd like to do is control the clock ticks for a <em>non-realtime</em> Cesium application. Imagine there's expensive code running, plus I want to give the viewer time to load the tiles before continuing. So <strong>how do I disable automatic ticking, and then call tick() manually</strong> when my code is ready for it?</p>
  
  <p>Docs for <strong>Cesium.Clock</strong> say "The clock will only tick when both Clock#canAnimate and Clock#shouldAnimate are true." but that's not what I'm getting.
  What I currently see:</p>
  
  <pre><code>viewer.clock.canAnimate = false;
  viewer.clock.shouldAnimate = false;
  viewer.clock.onTick.addEventListener(function(clock){
      console.log("Tick");
  });
  </code></pre>
  
  <p>The result in the console shows the clock still ticking:</p>
  
  <pre><code>Tick
  Tick
  Tick
  Tick
  ...
  </code></pre>
  
  <p>What I'd like to do:</p>
  
  <pre><code>viewer.clock.stopTicking(); // or whatever that command would be...
  while (someCondition){
      // run expensive code
      tick(); // issue manual tick
  }
  </code></pre>
  
  <p>Thanks for your help!
  Max</p>