ReadMe.md

NavMesh Generator

This JavaScript library allows to generate 2D navigation meshes for pathfinding.

It can be used, for instance, with this pathfinding implementation: mikewesthad/navmesh.

Used work

This implementation is strongly inspired from NMGen Study a Java one by Stephen A. Pratt.

This implementation differs a bit from the original:

• It's only 2D instead of 3D
• It uses objects for points instead of pointer-like in arrays of numbers
• The rasterization comes from other sources because of the 2d focus
• The partialFloodRegion function was rewritten to fix an issue
• An algorithm to filter vertices that are not on a border was added

The original Java implementation was also inspired from Recast itself.

A scan-line polygon fill algorithm

The original implementation was done by Darel Rex Finley.

The implementation used in this library differs with the following:

• It handles float vertices so it focusses on pixels center
• It is conservative to thin vertical or horizontal polygons

Demonstrations

An isometric example

This is a modified version of an official example of GDevelop where a character moves to the pointer with a left click. The art was done by Mickael Hoarau.

Try it on itch.io

An AI example

This is a modified version of an official example of GDevelop where enemies follow the player.

Try it on itch.io

Squares at random positions

Try it on itch.io

Two sizes of moving objects and obstacle dragging

Try it on itch.io

How to use it

The algorithm builds a mesh from a given area and a list of polygon obstacles.

import { NavMeshGenerator } from "NavMeshGenerator";

const areaLeftBound = 0;
const areaTopBound = 0;
const areaRightBound = 800;
const areaBottomBound = 600;
const rasterizationCellSize = 10;
const navMeshGenerator = new NavMeshGenerator(
  areaLeftBound,
  areaTopBound,
  areaRightBound,
  areaBottomBound,
  rasterizationCellSize
);

const obstacles = [[
  { x: 300, y: 200 },
  { x: 500, y: 200 },
  { x: 500, y: 400 },
  { x: 300, y: 400 },
]];
const obstacleCellPadding = 0;
const navMeshPolygons = navMeshGenerator.buildNavMesh(
  obstacles,
  obstacleCellPadding
);

If you are using mikewesthad/navmesh, you can directly use the mesh to find paths.

const navMesh = new NavMesh(navMeshPolygons);
const path = navMesh.findPath({ x: 100, y: 300 }, { x: 700, y: 300 });

In this case, you need this additional import.

import { NavMesh } from "navmesh";

Changelog

Version 1.0.3

• ES5 compatibility

Version 1.0.0

• First version