luxe: astar

• AStar

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AStar

import "luxe: astar" for AStar

A generic implementation of A* pathfinding in luxe.

For details about the pathfinding and things like costs, heuristics and implementation details, please see https://www.redblobgames.com/pathfinding/a-star/introduction.html

AStar.MAX

AStar.MAX : Num

A value that defaults to 250, for the max number of iterations that will be considered valid. If the max is reached, no path is returned. To update it, use Astar.MAX = 400.

AStar.MAX

AStar.MAX=(v : Num) : unknown

no docs found

AStar.path2D(…)

AStar.path2D(start : Vec, end : Vec, cost_get_fn : Fn, neighbors_get_fn : Fn, heuristic_fn : Fn) : List

Returns a path between start and end if one was found, or null otherwise. The path is a List of nodes received from start, end or neighbors_get_fn and are unmodified.

Note: Check if start/end are walkable before calling this function.

Cost-calculating Function:

//no cost?
_cost_get_fn = Fn.new {|from, to| 1 }
//cost from a tilemap, simple (fake) example
_cost_get_fn = Fn.new {|from, to| tiles.get_cost(to.x, to.y) }

Getting the neighbors of a node:

_neighbors_get_fn = Fn.new {|node|
  var list = []
  //check above, below, left and right.
  if(is_walkable(node.x, node.y+1)) list.add(Node.new(node.x, node.y+1))
  if(is_walkable(node.x, node.y-1)) list.add(Node.new(node.x, node.y-1))
  if(is_walkable(node.x+1, node.y)) list.add(Node.new(node.x+1, node.y))
  if(is_walkable(node.x-1, node.y)) list.add(Node.new(node.x-1, node.y))
  return list
}

Getting the heuristic value of a point:

_heuristic_fn = Fn.new {|end, point|
  var manhattan = ((end.x - point.x).abs + (end.y - point.y).abs)
  return manhattan * 1.001 //fudge factor, see the linked articles on pathfinding
}

Getting a path:

get_path(start, end) {
  if(!is_walkable(start)) return null
  if(!is_walkable(end)) return null
  return AStar.path2D(start, end, _cost_get_fn, _neighbors_get_fn, _heuristic_fn)
}