title: How to handle animation that contains multiple objects in OpenGL?
body: <p>I need to create an OpenGL animation, which mainly contains two objects, a simple one (e.g. a plane) that consists of hundreds of vertexes, and a very complex one (e.g. a city) that contains hundreds of thousands of vertexes. Both two objects have been created indecently. Now I need to put both of them into an animation. For example, in the animation we are looking down at the city from the sky, while a plane flying through the screen. Since the city model is very complex and takes minutes to render, it is impossible to render both the plane and the city at every frame. So my question is, how to render multiple objects independently in OpenGL? Do I need to render the city at every frame? Can I kind of "fix" the city object and just refresh the plane at every frame?</p>
  
  <p>I've read references such as the Red Book etc. Maybe I don't get it but they seem not teach how to handle the above problem. Can someone help me out?</p>