Example CircuitBoardExample.cs

This example shows how to use the Pathfinding.ITraversalProvider interface to generate paths like on a circuit-board.

This example shows how to use the Pathfinding.ITraversalProvider interface to generate paths like on a circuit-board.I.e paths that do not share any node. The image below shows a test case when using the script to calculate 4 paths on a small grid. The visualization of the paths has been improved manually using an external photo-editing application.

The code has intentionally been left simple, so very little error checking and special case handling is done.

Note that finding paths on a circuit-board in an optimal way is a very hard problem (NP-Complete). For further information about that, see https://en.wikipedia.org/wiki/Multi-commodity_flow_problem.

Attach this script to any GameObject and fill in the 'items' array with the start and endpoints of each path.

using UnityEngine;
using System.Collections.Generic;
using Pathfinding;

[HelpURL("http://arongranberg.com/astar/docs/class_circuit_board_example.php")]
public class CircuitBoardExample : MonoBehaviour {
[System.Serializable]
public class Item {
public Transform start;
public Transform end;
}

public Item[] items;

class Blocker : ITraversalProvider {
public HashSet<GraphNode> blockedNodes = new HashSet<GraphNode>();

public bool CanTraverse (Path path, GraphNode node) {
// Override the default logic of which nodes can be traversed
return DefaultITraversalProvider.CanTraverse(path, node) && !blockedNodes.Contains(node);
}

public bool CanTraverse (Path path, GraphNode from, GraphNode to) {
return CanTraverse(path, to);
}

public uint GetTraversalCost (Path path, GraphNode node) {
// Use the default costs
return DefaultITraversalProvider.GetTraversalCost(path, node);
}

// This can be omitted in Unity 2021.3 and newer because a default implementation (returning true) can be used there.
public bool filterDiagonalGridConnections {
get {
return true;
}
}
}

void Update () {
var traversalProvider = new Blocker();

// Calculate all paths in sequence.
// It is important that they are not calculated in parallel
// as we need to make sure that the paths do not visit the same nodes.
// The result may vary significantly depending on the order in which
// the paths are calculated.
for (int index = 0; index < items.Length; index++) {
var item = items[index];

// Create new path object
ABPath path = ABPath.Construct(item.start.position, item.end.position);
path.traversalProvider = traversalProvider;
// Start calculating the path and put the path at the front of the queue
AstarPath.StartPath(path, true);

// Calculate the path immediately
path.BlockUntilCalculated();

// Make sure the remaining paths do not use the same nodes as this one
foreach (var node in path.path) {
traversalProvider.blockedNodes.Add(node);
}

// Draw the path in the scene view
Color color = AstarMath.IntToColor(index, 0.5f);
for (int i = 0; i < path.vectorPath.Count - 1; i++) {
Debug.DrawLine(path.vectorPath[i], path.vectorPath[i+1], color);
}
}
}
}