MultiTargetFree.cs

Shows how to find the closest target of many possible.In the pro version, this is easily achieved with the MultiTargetPath (see the corresponding example and docs), but in the free version it requires requesting multiple paths and comparing their lengths instead of a single path request. This is a bit more tedious and also slower than the MultiTargetPath, but it is possible nevertheless.

Since

Written for 3.2 but comments are added in places where adjustments would have to be made to get it to work on 3.1.x

using UnityEngine;
using Pathfinding;

public class MultiTargetFree : MonoBehaviour {
    /* The possible target objects */
    public Transform[] targets = new Transform[0];

    /* The paths currently being calculated or have been calculated */
    private Path[] lastPaths;

    /* Number of paths completed so far */
    private int numCompleted = 0;

    /* The calculated best path */
    private Path bestPath = null;

    /* Searches for the closest target */
    void Start () {
        SearchClosest();
    }

    /* Call to update the bestPath with the closest path one of the targets.
     * It will take a few frames for this to be calculated, the bestPath variable will be null in the meantime
     */
    public void SearchClosest () {
        //If any paths are currently being calculated, cancel them to avoid wasting processing power
        if (lastPaths != null)
            for (int i = 0; i < lastPaths.Length; i++)
                lastPaths[i].Error();

        //Create a new lastPaths array if necessary (can reuse the old one?)
        if (lastPaths == null || lastPaths.Length != targets.Length) lastPaths = new Path[targets.Length];

        //Reset variables
        bestPath = null;
        numCompleted = 0;

        //Loop through the targets
        for (int i = 0; i < targets.Length; i++) {
            //Create a new path to the target
            ABPath p = ABPath.Construct(transform.position, targets[i].position, OnTestPathComplete);

            /* Before version 3.2
             * Path p = new Path (transform.position,targets[i].position, OnTestPathComplete);
             */

            lastPaths[i] = p;

            //Request the path to be calculated, might take a few frames
            //This will call OnTestPathComplete when completed
            AstarPath.StartPath(p);
        }
    }

    /* Called when each path completes calculation */
    public void OnTestPathComplete (Path p) {
        if (p.error) {
            Debug.LogWarning("One target could not be reached!\n"+p.errorLog);
        }

        //Make sure this path is not an old one
        for (int i = 0; i < lastPaths.Length; i++) {
            if (lastPaths[i] == p) {
                numCompleted++;

                if (numCompleted >= lastPaths.Length) {
                    CompleteSearchClosest();
                }
                return;
            }
        }
    }

    /* Called when all paths have completed calculation */
    public void CompleteSearchClosest () {
        //Find the shortest path
        Path shortest = null;
        float shortestLength = float.PositiveInfinity;

        //Loop through the paths
        for (int i = 0; i < lastPaths.Length; i++) {
            //Get the total length of the path, will return infinity if the path had an error
            float length = lastPaths[i].GetTotalLength();

            if (shortest == null || length < shortestLength) {
                shortest = lastPaths[i];
                shortestLength = length;
            }
        }

        Debug.Log("Found a path which was "+shortestLength+ " long");

        bestPath = shortest;
    }

    public void Update () {
        //Highlight the best path in the editor when it is found
        if (bestPath != null && bestPath.vectorPath != null) {
            for (int i = 0; i < bestPath.vectorPath.Count-1; i++) {
                Debug.DrawLine(bestPath.vectorPath[i], bestPath.vectorPath[i+1], Color.green);
            }

            /* Before version 3.2
             * for (int i=0;i<bestPath.vectorPath.Length-1;i++) {
             */
        }
    }
}