title: How is the cloud animation in Weather app works?
body: <p>I'm building an app in which I'd like to have animations of weather like in the weather app , I mean when it shows the clouds moving and rain falling etc in the background, and also animations like the application CALM when you seen high quality videos on the background.</p>
  
  <p>My question is - are those just high quality videos / animations that just sits on the background of the view ? or is it another technology core animation / openGL etc.. ? if so which class handles those type of things?</p>
  
  <p>sorry if the question is too stupid , never handled those kind of animations ....  </p>
  
  <p>Thanks.</p>