Access random GameObject from List on another script.

Question

Sadly I've wasted quite a few hours trying to crack this using an Array, but I keep failing.

With an Array I've been able to select a random GameObject and populate an object field using...

 WayPointArray = (GameObject.FindGameObjectsWithTag("WayPoint"));

with

 other.GetComponent<NPC_AI>().WayPoint = NPCWayPoint;

To find a way to get my NPCs to walk to random waypoints.

Naturally rather than having my NPCs active across a large map, I'm trying to keep them local to the player. Having a map of Spawn and WayPoint objects which direct the NPCs where to walk to next within an area.

On 'Start' the WayPoint script finds GameObjects tagged with 'WayPoint', and when it's collider is triggered by an NPC, the script delivers a position for the NPC to go to. ...using the code exampled above.

Only the problem is, my coding isn't great and I can't get the individual Arrays to only find tagged WayPoints within a small distance from each other, building a mesh of points that help the NPCs go A>B rather than A>Z across the map. My limitations in code means each WayPoint finds every WayPoint Tag across the map. Not ideal.

So I've now turned to Lists instead (for the first time), finding that On Start I can now get each WayPoint to find each other within a distance using a collider. (Couldn't with an Array)

 public List<GameObject> WayPoints;
 void OnTriggerStay(Collider other)
 {
     if (other.tag == "WayPoint")
     {
         if (!WayPoints.Contains(other.gameObject))
         {
             WayPoints.Add(other.gameObject);
         }
     }
 }

With that working as hoped, I now have the opposite problem where I can't get my other NPC_AI script to select a random WayPoint GameObject from the above.

Is there anyone that can help? The only way I could easily get my WayPoints to find each other close by, was to switch to lists instead.

As I mentioned, I'm not brilliant at coding generally and have managed with Arrays till now, but Lists so far have been alien to me and not as similar as I was hoping.
Any help I'd be really grateful. Thank you!!

Answer 1

Hey there,

as this information is only needed to be created once and using colliders is smart but bad on performance let me introduce you to the wonderful world of editor scripts:

 #if UNITY_EDITOR
 using UnityEditor;
 using UnityEngine;
 
 //assuming your waypoint class has these variables:
 public class Waypoint : MonoBehaviour
 {
     public Waypoint[] nextWaypoints;
     // distance value of this specifc waypoint. if distance between 2 points is less then their dist sum you can move between them.
     public float maxWaypointDistance = 100f; // point of this is to give individual waypoints a way to generate a smaller grid..
 }
 
 public class EditorCustomCommands
 {
     [MenuItem("CustomCommand/Initialize Waypoints")]
     public static void initializeWaypoints()
     {
         //find all "waypoints" in the current open scene:
         var allWaypoints = UnityEngine.Object.FindObjectsOfType<Waypoint>();
         //create an array of buffer lists for neighbour waypoints of each waypoint:
         var waypointBuffer = new System.Collections.Generic.List<Waypoint>[allWaypoints.Length];
         for (int i = 0; i < allWaypoints.Length; i++)
         {
             for (int j = 0; j < allWaypoints.Length; j++)
             {
                 //check if the relation between these 2 points has already been discovered:
                 if (waypointBuffer[i].Contains(allWaypoints[j]))
                     continue;
                 //check if the distance between these 2 waypoints is less than their added max waypoint distances:
                 if (allWaypoints[i].maxWaypointDistance + allWaypoints[j].maxWaypointDistance > Vector3.Magnitude(allWaypoints[i].transform.position - allWaypoints[j].transform.position))
                 {
                     //in this case we can move between the 2 waypoints and thus buffer this information:
                     waypointBuffer[i].Add(allWaypoints[j]);
                     waypointBuffer[j].Add(allWaypoints[i]);
                 }
             }
         }
         // now we have processed all waypoints so it is time to save the information on the object:
         for (int i = 0; i < allWaypoints.Length; i++)
         {
             //this is needed to be able to save the changes in the scene later on:
             Undo.RecordObject(allWaypoints[i], "set new next waypoint array");
             allWaypoints[i].nextWaypoints = waypointBuffer[i].ToArray();
             //this is needed to be able to save the changes in the scene later on as well:
             PrefabUtility.RecordPrefabInstancePropertyModifications(allWaypoints[i]);
         }
     }
 }
 #endif

What this does (in theory at least) is create a button in your top menu in the editor which you can click to automatically set all waypoint relations in your current scene. These are then saved in the nextWaypoints array of each waypoint.

Let me know if anything in there is unclear. I hope the comments in the code explain everythin as needed.

Answer 2

Answer by elkawee · Nov 23, 2021 at 09:34 AM

the lazy way to do it would be linq

convert to array and reuse your old code

 using System.Linq;
 
 //  ... 
 WayPoint [] waypointsArray  = WayPoints.ToArray();
 yourOriginalMethodOfRandomSelection ( waypointsArray );
 //  ...

or keep the lists and work directly on them

 using System.Linq;
 // .... 
 var R  = new Random();
 var randomWP = WayPoints.Skip(R.Next(WayPoints.Count())).First();

both have a performance impact
which one is faster depends on how long your list is

( the collider idea is kinda clever :) )

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AlexGLFC · Nov 23, 2021 at 01:06 PM 0

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Thank you so much @elkawee, I did look into Linqs, but they just scrabbled my brain further.

My intention was for each waypoint to have only around 3-6 findable other waypoints on each. Thank you, the intention for the collider was to log other waypoints that are near on Start and then disable the collider after the Array was populated. So hopefully $$anonymous$$imal impact once it's done the job.

If I fail with what the Captain has suggested, using a script in the Editor to do the graft rather than in-game, I'll come back to your post and see if the Linq conversion method works. Again thank you

Access random GameObject from List on another script.

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