place 8 objects around a target gameObject in a circle ( like a compass )

Question

Hey there !

I'm trying to instantiate 8 different gameobjects around my character, but I don't really know the math behind it, to do it with Sin or Asin.

First I was trying to do a for cycle from 1-8, then tried to convert i to degrees then that back to vectors, but somewhere around I gave up on that try.

 for (int i = 1; i < 8; i++) {
     //Got the degree
     float degree = Mathf.Asin(i / 360.0f);
     //How to convert it to a vector ?
     Vector2 vector = ?;
     //Instantiating
     Vector3 newPos = new Vector3(vector.x, y, vector.z);
     GameObject go = Instantiate(GameObject.CreatePrimitive(PrimitiveType.Cube), newPos, Quaternion.identity);
 }

Does anyone know the math behind it ?

Answer 1

Best Answer

Answer by Bunny83 · Sep 18, 2015 at 10:53 AM

 float radius = 1f;
 for (int i = 0; i < 8; i++)
 {
     float angle = i * Mathf.PI*2f / 8;
     Vector3 newPos = new Vector3(Mathf.Cos(angle)*radius, y, Mathf.Sin(angle)*radius);
     GameObject go = Instantiate(GameObject.CreatePrimitive(PrimitiveType.Cube), newPos, Quaternion.identity);
 }

First of all all trigonometry functions work with radians and not degree (full circle is 2*PI). Second ASin only covers 180°. Next thing is you started your loop with "1" but ended it on "7" ( "< 8"). That's why you usually start at 0 and go up to 7 which are 8 values.

So all you need is Sin and Cos with equally spaced angles in radians.

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internationalfish · May 10, 2019 at 12:38 PM 0

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A very late thank you for this. Easily adapted to arbitrary numbers of objects, and the results are pretty cool on a variable squad of NavAgents for target position offsets. :)

Answer 2

Answer by elButterfingers · Oct 18, 2019 at 06:03 PM

im a bit late for this but for anyone struggling with this @Bunny83 pretty much gave me everything i needed but i wrapped it into a pretty function for any amount of objects and from any position in the world.

 public void instantiateInCircle(GameObject obj, Vector3 location, int howMany)
 {
     for (int i = 0; i < howMany; i++)
     {
         float radius = howMany;
         float angle = i * Mathf.PI * 2f / radius;
         Vector3 newPos = transform.position + (new Vector3(Mathf.Cos(angle) * radius, -2, Mathf.Sin(angle) * radius));
         Instantiate(obj, newPos, Quaternion.Euler(0, 0, 0));
     }
 }

full credit to @Bunny83 , math is not my thing. neither is programming hence why i came here in the first place LOL.

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Aethenosity · Apr 17 at 09:20 PM 1

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The parameter 'location' is never used. Did you perhaps mean to replace 'transform.position' with it?

Answer 3

I Extended a little bit more the implementation of @elButterfingers and @Bunny83 , I added some methods for and parameters to customize better the usages. I hope that be useful! Cheers!

 public class TestCreateObjectsInCircle : MonoBehaviour
 {
     public GameObject prefabToInstantiate;
 
     /// <summary>
     ///     Instantiates prefabs around center splited equality. 
     ///     The number of times indicated in <see cref="howMany" /> var is
     ///     the number of parts will be the circle cuted, with taking as a center the location,
     ///     and adding radius from it
     /// </summary>
     /// <param name="prefab">The object it will be intantiated</param>
     /// <param name="location">The center point of the circle</param>
     /// <param name="howMany">The number of parts the circle will be cut</param>
     /// <param name="radius">
     ///     The margin from center, if your center is at (1,1,1) and your radius is 3 
     ///     your final position can be (4,1,1) for example
     /// </param>
     /// <param name="yPosition">The yPostion for the instantiated prefabs</param>
     public void InstantiateInCircle(GameObject prefab, Vector3 location, int howMany, float radius, float yPosition)
     {
         float angleSection = Mathf.PI * 2f / howMany;
         for (int i = 0; i < howMany; i++)
         {
             float angle = i * angleSection;
             Vector3 newPos = location + new Vector3(Mathf.Cos(angle), 0, Mathf.Sin(angle)) * radius;
             newPos.y = yPosition;
             Instantiate(prefab, newPos, prefab.transform.rotation);
         }
     }

     public void InstantiateInCircle(GameObject prefab, Vector3 location, int howMany, float radius)
     {
         this.InstantiateInCircle(prefab, location, howMany, radius, location.y);
     }

     public void InstantiateInCircle(GameObject prefab, int howMany, float radius)
     {
         this.InstantiateInCircle(prefab, this.transform.position, howMany, radius);
     }

     // client EXAMPLE
     private void Start()
     {
          this.InstantiateInCircle(this.prefabToInstantiate, new Vector3(0,0,0), 24, 2, 2);
     }
 }

Answer 4

Answer by Bhujanga · Dec 02, 2020 at 12:41 AM

Thanks for this awesome script @Raikish How could I add rotation to the prefabs? I want to instantiate the enemies in a 3d environment, but the game is supposed to be viewed 2d. So I want the circle to be "upright", zero on the z.position for all the instantiated prefabs. I tried to add a vector3 rotation to the function, but somehow cant make it work.

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place 8 objects around a target gameObject in a circle ( like a compass )

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