Pfinder

Pathfinding library based on the A* algorithm, JPS, concepts.
Demo: https://jjcapellan.github.io/pfinder-demo/

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Features

• Suitable for static 2d grids.
• Can be used in browser and Node.
• Minimal size: 3Kb minified.
• Easy to use.
• No dependencies.
• Paths contains mainly significative points (start, direction changes, end).
• Cacheable paths (optional)
• Asynchronous mode (optional)

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Installation

Browser

There are two alternatives:

• Download the file pfinder.min.js to your proyect folder and add a reference in your html:

<script src = "pfinder.js"></script>

• Point a script tag to the CDN link:

<script src = "https://cdn.jsdelivr.net/gh/jjcapellan/pfinder@0.7.0/dist/pfinder.min.js"></script>

Important: The library methods are exposed into the global object Pfinder

NPM

npm i pfinder

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How to use

Basic use:

import * as Pfinder from 'pfinder';

// Representation of 2d space. (0 = walkable, 1 = obstacle). 
const map = [
    [0,1,0,0],
    [0,1,0,0],
    [0,0,0,1],
    [1,1,0,0]
    ];

// Transform the map to a grid of nodes
const grid = Pfinder.makeGrid(map);

// Search the path between (0,0) and (3,3)
let path = Pfinder.getPath(grid, 0, 0, 3, 3);

// getPath() returns the path as an array of points:
// [{x: 0, y: 0}, {x: 0, y: 2}, {x: 2, y: 2}, {x: 2, y: 3}, {x: 3, y: 3}]

Asynchronous use:

Pfinder can limit CPU usage by queuing tasks, and defining the maximum number of tasks per frame. A task is a call to getPath.
This system is intended for use in games within the main loop. Example:

/* Import and makeGrid code here */

// 1) Define the maximum number of tasks per frame (Optional. Default = 20).
// Sets maxPathsPerFrame = 10, at 60FPS this is equal to 600 getPath calls per second.
Pfinder.setMaxPathsPerFrame(10);

// 2) Introduce tasks to the queue using getPathAsync function.
// Here the task is "getPath(grid, 0, 0, 3, 3)".
// The last parameter is the callback which will receive the path
Pfinder.getPathAsync(grid, 0, 0, 3, 3, (path) => console.log(path));


// 3) Pfinder.update() will execute 10 tasks from the task queue.
// This function should be in the main loop of the game.
Pfinder.update();

Using cache:

For those cases where paths are frequently repeated, we can use getPathFromCache() instead of getPath(). This function first looks for the requested path in cache and if it does not find it, it calls the getPath() function and saves the new path.
Depending on the case, getPathFromCache() can improve performance significantly, especially on large maps where few paths are frequently required.
By default, the cache stores up to 1000 routes. Beyond this limit, the first saved route is deleted each time a new one is saved. By default, the cache stores up to 1000 routes. We can change this limit with the setMaxCacheSize() function.

Example:

import * as Pfinder from 'pfinder';

// Representation of 2d space. (0 = walkable, 1 = obstacle). 
const map = [
    [0,1,0,0],
    [0,1,0,0],
    [0,0,0,1],
    [1,1,0,0]
    ];

// Transform the map to a grid of nodes
const grid = Pfinder.makeGrid(map);

// All possible paths in this map are 256, so we could reduce the cache size (default = 1000) to save some memory and cover the 100% cases.
// In larger maps we'll look for a compromise between memory and performance.
Pfinder.setMaxCacheSize(256);

// Gets the path between (0,0) and (3,3) from cache if possible else calls to getPath() and saves the path in cache.
let path = Pfinder.getPathFromCache(grid, 0, 0, 3, 3);

// getPathFromCache() returns the path as an array of points:
// [{x: 0, y: 0}, {x: 0, y: 2}, {x: 2, y: 2}, {x: 2, y: 3}, {x: 3, y: 3}]

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API

makeGrid(map: number[][]) : Object[][]

Converts 2d array of numbers to 2d array of nodes.
Parameters:

• map: 2d array of numbers representing a 2d space (0 = walkable, non 0 = obstacle).

Returns:
2d array of nodes used by other functions to search paths.

getPath(grid: Object[][], x0: number, y0: number, x1: number, y1: number): (Object[] | null)

Calculates the required path.
Parameters:

• grid : 2d array of nodes.
• x0 : x-coordinate of the path origin.
• y0 : y-coordinate of the path origin.
• x1 : x-coordinate of the path end.
• y1 : y-coordinate of the path end.

Returns:
Required path as an array of points (example: [{x: x0,y: y0}, {x: 2, y: 3}, ... , {x: x1, y: y1}]). If required path is not found, returns null.

getPathAsync(grid: Object[][], x0: number, y0: number, x1: number, y1: number, callback: function): void

Calls getPath() asynchronously. Specifically, it creates a task and adds it to a queue. This task will be executed after call update() method. Parameters:

• grid : 2d array of nodes.
• x0 : x-coordinate of the path origin.
• y0 : y-coordinate of the path origin.
• x1 : x-coordinate of the path end.
• y1 : y-coordinate of the path end.
• callback: callback function which receives the path as parameter.

getPathFromCache(grid: Object[][], x0: number, y0: number, x1: number, y1: number): (Object[] | null)

Gets required path. Before calculating the path, searchs it in cache.Depending on the case, it can improve performance significantly, especially on large maps where few paths are frequently required.

Parameters:

• grid : 2d array of nodes.
• x0 : x-coordinate of the path origin.
• y0 : y-coordinate of the path origin.
• x1 : x-coordinate of the path end.
• y1 : y-coordinate of the path end.

Returns:
Required path as an array of points (example: [{x: x0,y: y0}, {x: 2, y: 3}, ... , {x: x1, y: y1}]). If required path is not found, returns null.

setMaxCacheSize(size: number): void

Sets the number of max stored paths in cache.
Parameters:

• size : number of max stored paths in cache.

setMaxPathsPerFrame(n: number): void

Sets the maximum number of calls to getPath() executed per frame. Default = 20. Parameters:

• n: maximum number of calls to getPath() executed per frame.

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License

Pfinder is licensed under the terms of the MIT open source license.