游戏中如何实现大地图

About the specific issue of a big seamless world (like WoW) vs. game engine scenes. Since all floating point math starts to suffer accuracy errors with
to big values, you can't create a big seamless world that stretches forever in each direction as one scene. No game can. It would just be to demanding to load it all and the accuracy problems would become worse and worse the further you get from the origin.

The way you make big seamless worlds work is by using a technique commonly called "paging", where you basically break your whole world into a grid, where each cell is some specific size, say 512x515 units, and contains all the static geometry inside it. You
then render the grid the player is in plus the eight surrounding him.

The terrain (ground you walk on) you deal with a technique called streaming (or it can also be broken into grids) which allows you to stream the terrain data from disk and only hold the data you need in memory.

You would basically have an empty scene in unity, and have your own terrain + object formats. There is no way to create a BIG seamless world as "one big mesh" (for the terrain).