Question Detect if gameobject has empty space to spawn in

I currently have a 2D gameobject going to a random location when the game starts, but I want it to check if it collides with anything before it spawns in, and if it does the gameobject will generate a new random location. How can I do this?

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class EnemySpawn : MonoBehaviour
6. {
7.     private float startX;
8.     private float startY;
9.     private Transform trans;
10.  
11.     private void Start()
12.     {
13.         trans = GetComponent<Transform>();
14.         startX = Random.Range(-8, 8);
15.         startY = Random.Range(-4, 4);
16.         trans.position = new Vector2(startX, startY);
17.     }
18. }
19.  
20.  

 

There are a number of ways you could do it, but Physics.CheckSphere is probably the best option.
https://docs.unity3d.com/ScriptReference/Physics.CheckSphere.html

 

Sorry, I forgot to mention that it is in 2d. Will Physics.CheckBox work fine? Also, what do the docs mean by halfextent, layermask, and queryTriggerInteraction? I wasn't able to make sense of their explanation

 

Either of them will work fine. 2D is just 3D from a single perspective. One will just check a circle around your chosen area, and the other a square.

Halfextents is one half the size of the box in local space. Where the extents would be the "extents" of the bounds of the box, half extents are literally half of that. A layermask defines what layers are checked so that layers that don't need to be checked can be bypassed. queryTriggerInteraction specifies whether the check will check trigger colliders as well, or just colliders without triggers.

https://docs.unity3d.com/ScriptReference/BoxcastCommand-halfExtents.html
https://docs.unity3d.com/ScriptReference/LayerMask.html
https://docs.unity3d.com/ScriptReference/QueryTriggerInteraction.html

 

Thanks for explaining, this makes more sense now. I tried implement Physics.CheckBox but it didn't work, what can I do to fix it?

Code (CSharp):

1. using UnityEngine;
2.  
3. public class EnemySpawn : MonoBehaviour
4. {
5.     private float startX;
6.     private float startY;
7.     private Transform trans;
8.     private Vector3 pos;
9.  
10.     private void Start()
11.     {
12.         trans = GetComponent<Transform>();
13.         startX = Random.Range(-8, 8);
14.         startY = Random.Range(-4, 4);
15.         trans.position = new Vector2(startX, startY);
16.  
17.         pos = trans.position;
18.         IsColliding();
19.  
20.         if (IsColliding() == true)
21.         {
22.      
23.             startX = Random.Range(-8, 8);
24.             startY = Random.Range(-4, 4);
25.             trans.position = new Vector2(startX, startY);
26.             pos = trans.position;
27.  
28.         }
29.     }
30.  
31.     private bool IsColliding()
32.     {
33.         if (Physics.CheckBox(pos, trans.localScale) == true)
34.         {
35.             return true;
36.         }
37.         else
38.         {
39.             return false;
40.         }
41.     }
42. }

 

If this is 2d, you should be using methods from the

Physics2D

class.

 

Aah yes, spiney is right. Assuming you're using 2D colliders, try Physics2D.OverlapBox. If it's 2.5D you'll need to use the corresponding 2D or 3D physics to make them interact.
https://docs.unity3d.com/ScriptReference/Physics2D.OverlapBox.html

 

Thank you, changing Physics.CheckBox to Physics2D.OverlapBox and adding the correct arguments worked