   terrain paging?
  Can someone tell me what terrain paging basically is? I searched the web and gamedev but couldnt find a complete answer.All I know of it is basically this:So basically the white planes are the terrain 'chunks' and the middle thing is the player. The 'chunks' get loaded (and rendered) and unloaded as the player passes the border of the current chunk that he is on.I'm not using pure opengl or directx so I just want to learn about the concept of it.   
  When you have very large terrains, lets say a few gigs of data and textures (mega-textures), you don't want to load the whole terrain at once, because the player is only able to see a very small portion of it. I will explain it by delivering a simple example:You need to handle a large terrain, a whole world. First you need to subdivide it into a grid. Each tile is saved as tile_x_y.dat. Now you can derive the tile position x,y by the players position px,py. If you just want to know where the player is standing this would be enough, but the player often can look farther than the size of a single tile. So you can load not only the tile on which the player stands, but the neighbor tiles too (which results in your animated gif). When the player moves on and steps on a new tile you need to fetch the next tiles and you can unload tiles which are no longer used. To keep the loading frequency of tiles low, you can use a cache of the least resent used(LRU cache) tiles to avoid reloading tiles often needed (i.e. when your player runs around a small town).