Issue with Destroying Gameobjects

Question

Hi, I need some guidance from the community. I've made a scenario where an NPC will spawn from the spawn point and move towards the exit with the help of NavMesh. I got the spawning and the path-finding to work however I'm unable to destroy the game object when it reaches the exit. A screenshot is as attached: alt text

Here are the codes I've used in this scene: Spawning Script

 public class NPC_Spawner : MonoBehaviour
 {
     public GameObject npc;
     public GameObject exit;
 
     void Start ()
     {
         Invoke("SpawnNPC", 2);
     }
 
     public void SpawnNPC ()
     {
         GameObject na = (GameObject) Instantiate(npc, this.transform.position, Quaternion.identity);
         na.GetComponent<NPC_Behaviour>().exit = exit.transform;
         // if (na.transform.position == exit.transform.position)
         // {
         //     Destroy(na);
         //     Debug.Log("Collision Detected!!!");
         // }
         Invoke("SpawnNPC", Random.Range(2,5));
     }
 }

NPC Behaviour Script

 using UnityEngine;
 using UnityEngine.AI;
 
 
 public class NPC_Behaviour : MonoBehaviour
 {
     public Transform exit;
 
     void Start()
     {
         UnityEngine.AI.NavMeshAgent agent = GetComponent<UnityEngine.AI.NavMeshAgent>();
         agent.destination = exit.position;
     }
 }

Exit Script

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class NPC_Exit : MonoBehaviour
 {
     void OnTriggerEnter(Collider col)
     {
         if (col.gameObject.tag == "NPC")
         {
             Debug.Log("Collision Detected");
             Destroy(col.gameObject);
         }        
     }
 }

The box collider for exit is set 'Is Trigger'. Please let me know what I did wrong here. Your help is much appreciated.

Answer 1

Best Answer

Answer by The_Three_Vs · Mar 31, 2020 at 03:56 PM

Do either your exit or your NPC object have a Rigidbody? In order for OnTriggerEnter to be called, at least one of the colliding objects must have a Rigidbody. If this is the case, I would recommend putting a Rigidbody on the exit and unchecking gravity.

Hope this helps!

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Hodoer · Apr 01, 2020 at 01:52 AM 0

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Thank you very much, this works for me. One question though if it's not too troublesome, what's functionally different between onTriggerEnter and onCollisionEnter? Implementing a Rigidbody works for onTriggerEnter but does not work for onCollisionEnter.

The_Three_Vs Hodoer · Apr 01, 2020 at 02:04 AM 0

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When isTrigger is on, the collider will not interact with other colliders, so it's effectively intangible. Because of this, "collisions" do not happen and OnCollisionEnter isn't called, but objects can still enter the trigger area and activate OnTriggerEnter. Furthermore, while OnTriggerEnter passes in a collider, ex. the other object's BoxCollider, OnCollisionEnter passes in a Collision, which contains additional information about the collision like contact points and impact velocity.

Issue with Destroying Gameobjects

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