Pathfinding on large map

Question

I\'m creating a game with a 10,000 by 10,000 map.
I would like for a user to be able to set a location and have the computer instantly find the best path.
However, since

Answer 1

Since the map is 10.000 x 10.000 the number of nodes is 100.000.000. Using a straightforward implementation of A* would be impractical and certainly wouldn't make the game scalable in mapsize.

I would recommend you to use the following solution, which is essentially what you were thinking:

HPA* (Hierarchical Path A*). This method creates different hierarchies of map. You may automate the process by saying every block of 100x100 pixels is a region. Then, for every block, we need to find the adjacent blocks and where the entries and exits for each block is. If the connection between the two blocks is more than a node then we use two nodes to represent the problem. This image explains the new graph that we're trying to build. (Black=obstacle and grey are connecting nodes between blocks).

This method provides good results as can be seen from an execution using maps from the game Baldur's Gate with every block being 10x10.

For more information read this article from Nathan Sturtevant (he is one of the most succesful path-finding researcher when it comes to games). https://skatgame.net/mburo/ps/path.pdf

For an explanation of HPA please check this lecture of Sturtevant (min 43:50 for HPA). https://www.youtube.com/watch?v=BVd5f66U4Rw

Also, if you want to see HPA* in action check this video that Sturtevant made: https://www.youtube.com/watch?v=l7YQ5_Nbifo