esengine/docs/en/modules/pathfinding/index.md

Pathfinding System

@esengine/pathfinding provides a complete 2D pathfinding solution including A* algorithm, grid maps, navigation meshes, and path smoothing.

Installation

npm install @esengine/pathfinding

Quick Start

Grid Map Pathfinding

import { createGridMap, createAStarPathfinder } from '@esengine/pathfinding';

// Create 20x20 grid
const grid = createGridMap(20, 20);

// Set obstacles
grid.setWalkable(5, 5, false);
grid.setWalkable(5, 6, false);

// Create pathfinder
const pathfinder = createAStarPathfinder(grid);

// Find path
const result = pathfinder.findPath(0, 0, 15, 15);

if (result.found) {
    console.log('Path found!');
    console.log('Path:', result.path);
    console.log('Cost:', result.cost);
}

NavMesh Pathfinding

import { createNavMesh } from '@esengine/pathfinding';

const navmesh = createNavMesh();

// Add polygon areas
navmesh.addPolygon([
    { x: 0, y: 0 }, { x: 10, y: 0 },
    { x: 10, y: 10 }, { x: 0, y: 10 }
]);

navmesh.addPolygon([
    { x: 10, y: 0 }, { x: 20, y: 0 },
    { x: 20, y: 10 }, { x: 10, y: 10 }
]);

// Auto-build connections
navmesh.build();

// Find path
const result = navmesh.findPath(1, 1, 18, 8);

Core Concepts

IPathResult

interface IPathResult {
    readonly found: boolean;        // Path found
    readonly path: readonly IPoint[];// Path points
    readonly cost: number;          // Total cost
    readonly nodesSearched: number; // Nodes searched
}

IPathfindingOptions

interface IPathfindingOptions {
    maxNodes?: number;        // Max search nodes (default 10000)
    heuristicWeight?: number; // Heuristic weight (>1 faster but may be suboptimal)
    allowDiagonal?: boolean;  // Allow diagonal movement (default true)
    avoidCorners?: boolean;   // Avoid corner cutting (default true)
}

Heuristic Functions

Function	Use Case	Description
manhattanDistance	4-directional	Manhattan distance
euclideanDistance	Any direction	Euclidean distance
chebyshevDistance	8-directional	Diagonal cost = 1
octileDistance	8-directional	Diagonal cost = √2 (default)

Grid Map API

createGridMap

function createGridMap(
    width: number,
    height: number,
    options?: IGridMapOptions
): GridMap

Options:

Property	Type	Default	Description
allowDiagonal	boolean	true	Allow diagonal movement
diagonalCost	number	√2	Diagonal movement cost
avoidCorners	boolean	true	Avoid corner cutting
heuristic	HeuristicFunction	octileDistance	Heuristic function

Map Operations

// Check/set walkability
grid.isWalkable(x, y);
grid.setWalkable(x, y, false);

// Set movement cost (e.g., swamp, sand)
grid.setCost(x, y, 2);

// Set rectangle region
grid.setRectWalkable(0, 0, 5, 5, false);

// Load from array (0=walkable, non-0=blocked)
grid.loadFromArray([
    [0, 0, 0, 1, 0],
    [0, 1, 0, 1, 0]
]);

// Load from string (.=walkable, #=blocked)
grid.loadFromString(`
.....
.#.#.
`);

// Export and reset
console.log(grid.toString());
grid.reset();

A* Pathfinder API

const pathfinder = createAStarPathfinder(grid);

const result = pathfinder.findPath(
    startX, startY,
    endX, endY,
    { maxNodes: 5000, heuristicWeight: 1.5 }
);

// Pathfinder is reusable
pathfinder.findPath(0, 0, 10, 10);
pathfinder.findPath(5, 5, 15, 15);

NavMesh API

const navmesh = createNavMesh();

// Add convex polygons
const id1 = navmesh.addPolygon(vertices1);
const id2 = navmesh.addPolygon(vertices2);

// Auto-detect shared edges
navmesh.build();

// Or manually set connections
navmesh.setConnection(id1, id2, {
    left: { x: 10, y: 0 },
    right: { x: 10, y: 10 }
});

// Query and pathfind
const polygon = navmesh.findPolygonAt(5, 5);
navmesh.isWalkable(5, 5);
const result = navmesh.findPath(1, 1, 18, 8);

Path Smoothing

Line of Sight Smoothing

Remove unnecessary waypoints:

import { createLineOfSightSmoother } from '@esengine/pathfinding';

const smoother = createLineOfSightSmoother();
const smoothedPath = smoother.smooth(result.path, grid);

Curve Smoothing

Catmull-Rom spline:

import { createCatmullRomSmoother } from '@esengine/pathfinding';

const smoother = createCatmullRomSmoother(5, 0.5);
const curvedPath = smoother.smooth(result.path, grid);

Combined Smoothing

import { createCombinedSmoother } from '@esengine/pathfinding';

const smoother = createCombinedSmoother(5, 0.5);
const finalPath = smoother.smooth(result.path, grid);

Line of Sight Functions

import { bresenhamLineOfSight, raycastLineOfSight } from '@esengine/pathfinding';

const hasLOS = bresenhamLineOfSight(x1, y1, x2, y2, grid);
const hasLOS2 = raycastLineOfSight(x1, y1, x2, y2, grid, 0.5);

Practical Examples

Dynamic Obstacles

class DynamicPathfinding {
    private grid: GridMap;
    private pathfinder: AStarPathfinder;
    private dynamicObstacles: Set<string> = new Set();

    addDynamicObstacle(x: number, y: number): void {
        this.dynamicObstacles.add(`${x},${y}`);
        this.grid.setWalkable(x, y, false);
    }

    removeDynamicObstacle(x: number, y: number): void {
        this.dynamicObstacles.delete(`${x},${y}`);
        this.grid.setWalkable(x, y, true);
    }
}

Terrain Costs

const grid = createGridMap(50, 50);

// Normal ground - cost 1 (default)
// Sand - cost 2
for (let y = 10; y < 20; y++) {
    for (let x = 0; x < 50; x++) {
        grid.setCost(x, y, 2);
    }
}

// Swamp - cost 4
for (let y = 30; y < 35; y++) {
    for (let x = 20; x < 30; x++) {
        grid.setCost(x, y, 4);
    }
}

Blueprint Nodes

• FindPath - Find path
• FindPathSmooth - Find and smooth path
• IsWalkable - Check walkability
• GetPathLength - Get path point count
• GetPathDistance - Get total path distance
• GetPathPoint - Get specific path point
• MoveAlongPath - Move along path
• HasLineOfSight - Check line of sight

Performance Tips

1. Limit search range: { maxNodes: 1000 }
2. Use heuristic weight: { heuristicWeight: 1.5 } (faster but may not be optimal)
3. Reuse pathfinder instances
4. Use NavMesh for complex terrain
5. Choose appropriate heuristic for movement type

Grid vs NavMesh

Feature	GridMap	NavMesh
Use Case	Regular tile maps	Complex polygon terrain
Memory	Higher (width × height)	Lower (polygon count)
Precision	Grid-aligned	Continuous coordinates
Dynamic Updates	Easy	Requires rebuild
Setup Complexity	Simple	More complex