Talk:Proposals/Obsolete Proposals/Macro Pathfinding

From UFO:AI

Additional thoughts

Possibly, there could be different types of waypoint for the AI in addition to the regular waypoint that only serves to be part of the graph. For example:

  • Attack waypoints could help the AI determine where strategic targets are. Actors that have been given an attack role would randomly select one attack waypoint as their destination, attempt to fight their way there and destroy wahtever target is in that area. On successfully completing their attack mission, they would proceed to the next target or if no target was available, revert to the default alien behaviour.
  • Defense waypoints could be used by mappers to ensure that the aliens spend some of their manpower to defending their own positions. This would be especially useful in UFO recovery missions and alien base missions. Aliens with a defensive role would proceed to a randomly chosen defense waypoint and then idle in that area, reserving their TUs for Reaction Fire. Enemies approaching closely enough should be engaged.
  • Patrol waypoints could be used by mappers to ensure that areas of the map are visited by the AI. Actors on a patrol mission would proceed to a randomly chosen patrol waypoint and, upon arriving, proceed to a randomly chosen other waypoint, repeating the process until they were killed or encountered an enemy. This type of waypoint would probably not result in a noticeable difference in behaviour of the AI.

The amount of aliens assigned attack, defense and patrol roles should depend on the mission type and the existence or nonexistence of the relevant waypoints. --BTAxis 22:11, 19 August 2007 (CEST)

Alternative Suggestion

I am still quite clueless about the code base, but having a look at cmodel.c (which I suspect to be the path finding algorithm) I have the feeling things could more easily improved by switching the algorithm and not by adding another layer ontop of it.

First thing would be to us Dijkstra's algorithm instead of looping over and over again over terrain that's not of interest. Second step would be to use the A* algorithm for long range path searches or simply any path searches that have a known target and don't need to create a path map for a whole area. As most maps are not very mazelike A* should give quite good results using the Taxicab Distance as heuristic.

  • Sounds like a good idea. Of course the trouble is finding someone who can implement it... By the way, do you think that approach would be sufficiently fast for the (time-critical) application of plotting a path when the user clicks on a part of the map? A noticeable delay here really isn't acceptable. Perhaps using another layer may be required to speed up the calculation by doing two short-range plots (from actor to nearest waypoint and then from waypoint nearest destination to destination) and one long-range plot per a waypoint system, as described in the article or by a more efficient means. --BTAxis 01:03, 4 October 2007 (CEST)
  • Depends a bit an the layout of the map. A* is quite good if walking into the right direction helps. A* doesn't like dead ends that have a huge area.
    • Shelter is one such map (in fact, it was built around the very concept). Other maps are better in this respect, though I don't know how maze-like A* considers large buildings to be, like the one in the estate map. Base assemblies may also prove to be a bit problematic, especially with advanced base building. --BTAxis 12:42, 4 October 2007 (CEST)
  • What's the maximum size of a map in squares?
    • I think the maximum is pretty big. I don't know what the largest reasonable size is for a map (taking FPS and such into account), but it can have at most 8 levels.
  • It should be possible to create the path map in the background following the mouse cursor or even for the whole map. That way the path would be ready before clicking. But this is a bit more tricky.