Detection within distance.

Unity Engine
1

I’m sure this has been discussed in other threads, but I don’t know what to search for and I found nothing. Now, if I had to do this only with one paticular object, everything would have been ok, but I want to check if different objects with a certain tag are close to the object that’s checking. Basicaly I want to detect objects. I can do this with 500 raycasts maybe, but I’m pretty sure this isn’t the right way to do it. Sorry for the bad explanation, but I wouldn’t have explained it better either on my own language :smile:

2

Put a rather large sphere object (with a collider) around the object and make it a trigger. Remove the renderer of course.

Then OnTriggerEnter() will tell you when something is close and OnTriggerExit() will tell you when something leaves.

3

Nice idea, but one problem comes to mind- if the object with the sphere is next to a wall, the sphere will clip through the wall and everything behind the wall, that touches the sphere will trigger the collider.

4

On such case do a ray cast between the player and the enemy, if it reaches the enemy no problem. Its a lot cheaper to do a ray cast in the odd situation than every frame.

5

Yes, but that’s my problem. How do I know to which enemy to do the raycast if they are 5 and only one is in range? Would I need something like a for-loop with all the enemies or something?

6

Have a list of current in range enemies which will be added OnTriggerEnter(). Then loop through those ones. You dont want to check every enemy just the ones close.

7

Thanks! And just a last question, which is pretty dumb, but how will I loop through the enemies in range. Sounds strange, but I haven’t looped between things, that change yet.

8

Assuming C#:

ArrayList m_enemiesInRange = new ArrayList(); // Init in start


foreach( GameObject in m_enemiesInRange )
{
     // Ray cast to enemy, if hit process whatever.
}
9

I’m using JavaScript, so from what I understand it would be.

var enemies = new Array();

for(i=0, enemies.Lenght, i++)
{
raycast to enemies[i].GameObject
}

And when a new enemy is added I would add it like
enemies[enemies.Lenght + 1] = the enemy.

Right ?

Just a question than. How will I remove the enemies from the array ?

10

Arrays/lists/etc. don’t magically resize when you try to access out-of-range elements; you need to allocate space first. Using .Add with an Array does that for you, but trying to access array[ array.length ] will just throw a null exception.

var enemies : Array;

function AddEnemy( e ) {
  enemies.Add( e );
}

function RemoveEnemy( e ) {
  for ( var ix : int = 0; ix < enemies.length; ix++ ) {
    if ( e == enemies[ix] ) {
      enemies.RemoveAt(ix);
      break;
    }
  }
}
11

Thanks for the help!