Pathfinding in Ruby

A pathfinding library in Ruby based on A* algorithm.

Inpired by python-pathfinding

Install

To install the library, use the gem command:

gem install pathfinding

Usage

This is a simple example to find a path using A*.

  1. Import the library: ruby require 'pathfinding'

  2. Create a map using a 2D-list. Any value smaller or equal to 0 describes a walkable node. Any number bigger than 0 describes an obstacle. In this example, we added an obstacle in the middle.

    matrix = [
[0, 0, 0],
[0, 1, 0],
[0, 0, 0]
]

    Note: you can use negative values to describe different types of obstacles.

  3. Create a new grid from this map representation. This will create Nodes instances for every element of the map.

    grid = Grid.new(matrix)

  4. Set the start and end point from the map. In this example, the start point is on top-left and the end point is on bottom-right.

    start_node = grid.node(0, 0)
end_node = grid.node(2, 2)

  5. Create a new instance of the finder and run the find_path method. If a path from start to the end point exists, this method returns the list of nodes of the path. Else, it returns an empty list.

    finder = AStarFinder.new()
path = finder.find_path(start_node, end_node, grid)

    Note:

  • You can choose the heuristic function to use using the heuristic argument.
  • You can also choose the diagonal movements allowed using the diagonal_movement argument. ruby finder = AStarFinder.new(Heuristic::method(:manhattan), DiagonalMovement::NEVER) See the documentation for more details.
  1. Print the result (or do something else with it). ruby puts grid.to_s(path, start_node, end_node) The result should look like this: +---+ |sxx| | #x| | e| +---+
  2. +, - and | characters show the border around the map
  3. the blank space is a free field
  4. 's' marks the start
  5. 'e' marks the end
  6. '#' is the obstacle
  7. the 'x' characters mark the path from start to end

This is the whole example:

require 'pathfinding'

matrix = [
  [0, 0, 0],
  [0, 1, 0],
  [0, 0, 0]
]
grid = Grid.new(matrix)

start_node = grid.node(0, 0)
end_node = grid.node(2, 2)

finder = AStarFinder.new()
path = finder.find_path(start_node, end_node, grid)

puts grid.to_s(path, start_node, end_node)

Take a look at the examples/ folder for more examples.

Author

Quentin Deschamps

License

MIT