koobas.hobune.stream
How to check if Trigger is 'empty'?
Hi, all!
I have a trigger that turns the cursor green OnTriggerEnter, and red OnTriggerExit. However, sometimes that makes it turn red even when things are still inside of it.
I would like it to turn red only when it is completely empty, and turn green the moment anything is inside of it.
it would be along the lines of:
If( triggerIsEmpty){
GREEN!
}
else{
RED!
}
Anyone have some real code for my pseudo code? I could only find Enter, Exit, and Stay, and I don't think that that will work out for me.
Thanks!- YA
This might be a bit of a overkill.
How about this:
public class SlightAdvanceTrigger : MonoBehaviour {
private int _count;
void Start() {
_count = 0;
//You can setup the trigger here in script, or in the editor, doesn't really matter
}
void OnTriggerEnter( Collider other ) {
++_count;
}
void OnTriggerExit( Collider other ) {
--_count;
}
bool isEmpty() {
return _count == 0;
}
}
Please note that I do not know whether if the OnTriggerExit() will be called when a gameobject is destroyed in the trigger. If you have that sort of action, you will need to keep track of the gameobject using a List< T >, and reset the _count accordingly everytime you need to access the _count or isEmpty().
Ha we came up with the same solution. I believe a solution with only OnTriggerStay() could be made too.
How to do it using just OnTriggerStay()? Do we need a collection to check whether if a certain gameObject in the trigger is already counted? Or is it some other way that I did not think of?
This is how I thought it would go. I was hoping for a magic function but it's not like this is hard or anything. Thanks, guys! - On a side note, I would be interested on how you could use OnTriggerStay for this.
Would it be close to:
function OnTriggerStay (other : Collider) {
if (other)
GREEN!
else RED!
}
Well, shoot. It doesn't detect when enemies die -_- How would I go about this, now?
There are 2 ways to approach this:
Trigger Notification
Notify.cs
...
using System.Collections.Generic;
public class Notify : $$anonymous$$onoBehavior {
public List<SlightAdvanceTrigger> advTriggers;
//Can be called by Send$$anonymous$$essage() when the enemy dies
public void Die() {
foreach( SlightAdvanceTrigger t in advTriggers ) {
t.Decrease();
}
}
}
SlightAdvanceTrigger.cs
public class SlightAdvanceTrigger : $$anonymous$$onoBehaviour {
private int _count;
void Start() {
_count = 0;
}
void OnTriggerEnter( Collider other ) {
++_count;
Notify n = other.gameObject.GetComponent<Notify>();
if( n == null ) {
n = other.gameObject.AddComponent<Notify>();
n.advTriggers = new List<SlightAdvanceTrigger>();
}
n.advTriggers.Add( this );
}
void OnTriggerExit( Collider other ) {
--_count;
n.AdvTriggers.Remove( this );
}
bool isEmpty() {
return _count == 0;
}
public void Decrease() {
--_count;
}
}
I know this is a bit old now. But incase anyone finds it in search.
The most simple way to do this is using the OnTriggerStay, and setting a bool to true when the frame starts, and then false if there are any active collisions. I really don't know why unity doesn't give you access to a list of all active collisions that a collider has, then you could just check the count on a collider.
public class SlightAdvanceTrigger : MonoBehaviour {
public bool isEmpty;
void FixedUpdate()
{
isEmpty = true;
}
void OnTriggerStay(Collider other)
{
isEmpty = false;
}
}
Thanks for the answer, man! This is old, and I am pretty sure I ended up going with the counting method. Hopefully this will help anyone else that stumbles over here. thanks again!
You could keep track with a counter of how many objects are in the trigger zone.
private int counter = 0;
void OnTriggerEnter(Collider other) {
counter++;
}
void OnTriggerExit(Collider other) {
counter--;
}
and then your pseudocode, which is probably placed in Update(), can be changed to :
if (counter == 0){
GREEN!
}else{
RED!
}
Is there any way to check if a collider is empty without using the OnTrigger functions?
I wouldn't think so that seems to be the only way to detect colliders..?
An alternative to using Triggers:
public Renderer myRenderer;
public Transform checkOrigin;
public float checkRadius;
public LayerMask checkMask;
void Update()
{
Collider[] checkResults = new Collider[1];
//OverlapSphereNonAlloc does not create garbage
int collidersHit = Physics.OverlapSphereNonAlloc(checkOrigin.position, checkRadius, checkResults, QueryTriggerInteraction.Ignore);
if(collidersHit > 0) {
myRenderer.material.color = Color.green;
}
else
{
myRenderer.material.color = Color.red;
}
}
