Beginner direction and magnitude question: CircleCollider2D

Hi there,

I checked several threads on direction's and magnitude's but couldn't figure out the following:
If I have a gameobject that solely carries a circlecollider2D, how can I get the position of a random point of the colliders boundary? I know that I can set random directions with random.range and set the vectors magnitude to the colliders radius, but I don't know how to do that properly in c#.

 

Code (CSharp):

1.     CircleCollider2D CC2D;
2.  
3.     Vector3 randomPointInRadius
4.     {
5.         get
6.         {
7.  
8.             float radius = CC2D.radius;
9.             Vector2 center = CC2D.bounds.center;
10.             Vector2 randomDirection = new Vector2(Random.Range(-1f,1f),Random.Range(-1f,1f)).normalized;
11.             float randomLength = Random.Range(0,radius);
12.             return center + randomDirection * randomLength;
13.         }
14.     }
15.    
16.     void Start ()
17.     {
18.         CC2D = GetComponent<CircleCollider2D>();
19.     }

Here, this is a pretty straight to the point calculation: using a random direction and a random length.
Maybe you're not familiar with getter/setter's, "randomPointInRadius" is a Vector3 randomized every time you "get" it.

So to move an object to a random spot within the CircleCollider just do this =
( gameObject.transform.position = randomPointInRadius )
But remember that "randomPointInRadius " changes every time you use it.

 

Could you explain more of what you are trying to do? aka why do you want to get a point on colliders boundary?

 

I have a circular "playfield" which is surrounded by another circle (a gameobject with a circlecollider2D) which represent the outer points of the players vision. The idea is, that I use the boundary of the circlecollider2D as random positions for enemy spawning.

Thanks for the code! This was basically what I needed except, that I wanted the position to always be on the colliders boundary. I adjusted your code to get a random position on the boundary everytime the "spawn-object" is enabled:

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class SpawnEnemies : MonoBehaviour {
5.  
6.     public GameObject enemyPrefab;
7.  
8.     public int amount;
9.  
10.     public GameObject spawnLocation;
11.     private float spawnRadius;
12.  
13.     public float spawnWait; // time between each enemy
14.  
15.     public bool randomSpawnLocation;
16.     public bool symmetricSpawnLocation;
17.  
18.     private Vector3 randomSpawnPoint;
19.  
20.  
21.     void OnEnable()
22.     {
23.         spawnLocation = GameObject.Find("SpawnLocation");
24.  
25.         SetRandomLocation();
26.  
27.         StartCoroutine(Spawn());
28.     }
29.  
30.  
31.     public void SetRandomLocation()
32.     {
33.         Random.seed = System.Environment.TickCount;
34.         float spawnRadius = spawnLocation.GetComponent<CircleCollider2D>().radius;
35.         Vector2 center = spawnLocation.GetComponent<CircleCollider2D>().bounds.center;
36.         Vector2 randomDirection = new Vector2(Random.Range(-1f, 1f), Random.Range(-1f, 1f)).normalized;
37.         randomSpawnPoint = center + randomDirection * spawnRadius;
38.     }
39.  
40.     IEnumerator Spawn()
41.     {
42.         if (randomSpawnLocation == true)
43.         {
44.             for (int i = 0; i < amount; i++)
45.             {
46.                 GameObject enemy = (GameObject)Instantiate(enemyPrefab, randomSpawnPoint, Quaternion.identity);
47.                 yield return new WaitForSeconds(spawnWait);
48.                 if (i == amount - 1)
49.                 {
50.                     Destroy(gameObject); // destroys the spawn when it finished spawning
51.                 }
52.             }
53.         }
54.      
55.         if (symmetricSpawnLocation == true)
56.         {
57.             // logic for symmetric spawns
58.         }
59.  
60.     }
61.  
62. }
63.  

There is another related problem: While the above code allows the spawning of all enemies at the same location, I want to implement symmetric spawning in the following sense:
If the amount of enemies to spawn is for example four:
Enemy 1 spawns at a random location on the boundary of the collider e.g. at center + Vector2(0f,1f)*spawnRadius, which is the right border;
Enemy 2 spawns at the opposite direction, relative to enemy 1. Enemy 3 spawns at the top (or bottom) border, while enemy 4 spawns at the bottom (top) border. While this is easy for 4 enemies, Iam looking for a general way to allow for e.g. odd spawning numbers where e.g. 3 enemies spawn at different locations but remain the same distance to it's nearest partner.