Spawn prefabs in a circle?

Question

I found this http://answers.unity3d.com/questions/170413/position-objects-around-other-object-forming-a-cir.html but the example given is in UnityScript and I've had trouble converting it to C#.

Is there a better way of doing the following:

1) Spawn enemies along a circular perimeter around a Vector3 point.

2) Vary the distance from the point.

If that is the best way, could someone help convert it to C#? Here it is again:

 function RandomCircle(center:Vector3, radius:float): Vector3 {
     // create random angle between 0 to 360 degrees
     var ang = Random.value * 360;
     var pos: Vector3;
     pos.x = center.x + radius * Mathf.Sin(ang * Mathf.Deg2Rad);
     pos.y = center.y + radius * Mathf.Cos(ang * Mathf.Deg2Rad);
     pos.z = center.z;
     return pos;
 }
 
 // How to use:
 
 var center = transform.position;
 for (i = 0; i < numObjects; i++){
       var pos = RandomCircle(center, 10);
      // make the object face the center
      var rot = Quaternion.FromToRotation(Vector3.forward, center-pos);
      Instantiate(prefab, pos, rot);
 }

Answer 1

Best Answer

Answer by robertbu · May 26, 2014 at 02:36 AM

Here is the completed C# translation. You had the type wrong on line 2 and line 13. You were missing an 'int' on line 11.

 using UnityEngine;
 using System.Collections;
 
 public class Example : MonoBehaviour {
 
     public int numObjects = 10;
     public GameObject prefab;
 
     void Start() {
         Vector3 center = transform.position;
         for (int i = 0; i < numObjects; i++){
             Vector3 pos = RandomCircle(center, 5.0f);
             Quaternion rot = Quaternion.FromToRotation(Vector3.forward, center-pos);
             Instantiate(prefab, pos, rot);
         }
     }
 
     Vector3 RandomCircle ( Vector3 center ,   float radius  ){
         float ang = Random.value * 360;
         Vector3 pos;
         pos.x = center.x + radius * Mathf.Sin(ang * Mathf.Deg2Rad);
         pos.y = center.y + radius * Mathf.Cos(ang * Mathf.Deg2Rad);
         pos.z = center.z;
         return pos;
     }
 }

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ANGRYSH4RK · May 26, 2014 at 03:06 AM 0

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thank you for the help! errors are gone

JasonC001 · Oct 01, 2014 at 06:34 PM 0

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Great start. Now I just need to randomize the radius and I'll have what I've been looking for for my project too. :)

Noxury · Jul 01, 2016 at 02:23 PM 0

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There is some error when an object is instantiated at Vector3(0,0,AnyNegativeZValue), it will flip around 180° on its Z-Axis, e.g. the car is upside down.

Bunny83 Noxury · Jul 01, 2016 at 04:29 PM 0

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You shouldn't use Quaternion.FromToRotation in such a case. Use Quaternion.LookRotation(pos-center)

Noxury Bunny83 · Jul 03, 2016 at 02:43 PM 0

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Great, thanks!

jakethegamedev · Dec 27, 2018 at 10:51 PM 0

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i don't know if this is possible but the prefabs spawn far away from the object that they are meant to spawn on and i would love to make them spawn closer if you know how plz tell me

Answer 2

Answer by CaptainTR · Nov 11, 2015 at 02:51 PM

alt text try this code

 int numObjects = 12;
 public GameObject prefab;

 void Start()
 {
     Vector3 center = transform.position;

     for (int i = 0; i < numObjects; i++)
     {
         int a = i * 30;


         Vector3 pos = RandomCircle(center, 1.0f ,a);
         Instantiate(prefab, pos, Quaternion.identity);
     }

 }

 Vector3 RandomCircle(Vector3 center, float radius,int a)
 {
     Debug.Log(a);
     float ang = a;
     Vector3 pos;
     pos.x = center.x + radius * Mathf.Sin(ang * Mathf.Deg2Rad);
     pos.y = center.y + radius * Mathf.Cos(ang * Mathf.Deg2Rad);
     pos.z = center.z;
     return pos;
 }

paylas.jpg (154.8 kB)

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Ziron999 · Nov 14, 2016 at 05:48 AM 0

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usually your plane will be 0,0,0 on all transforms to make it look right top down you would want to swap y/z:

  pos.z = center.z + radius * Mathf.Cos(ang * Mathf.Deg2Rad);
  pos.y = center.y;

IndieForger · Apr 29, 2017 at 10:59 PM 1

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You can replace

  int a = i * 30;

with

  int a = 360 / numObjects * i

which wil make a bit more dynamic.

thomaslay7 · Jun 02, 2018 at 09:29 PM 0

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how to make it using image? i had made like above . prefab = image. but when i try, the prefab out of canvas? when i try using 2d sprites, it's work like above.

Answer 3

Answer by tesan · Aug 09, 2017 at 07:33 PM

you can watch this plugin: http://u3d.as/Un7, I think it's what you want

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Spawn prefabs in a circle?

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