How can I make a gameobject "orbit" another

[CookieKirby]

I am trying to make one game object orbit a star by having a rigidbody look at the star and the planet itself is a child of the rigidbody. heres my code:

using UnityEngine;
using System.Collections;

public class Orbit : MonoBehaviour {

	public Vector3 Force;
	public Transform Target;
	
	void FixedUpdate()
	{
		transform.LookAt(Target);
		rigidbody.AddRelativeForce(Force);
	}
}

the Problem is that when i use this, the rigidbody looks at the star, but it does not move sideways relatively so that it will “orbit”, it simply moves sideways without turning. How can i fix this?

[AlejandroGorgal]

You can use a Slerp for that, here’s the code:

using UnityEngine;
using System.Collections;

public class GravityScript : MonoBehaviour 
{
    public Transform target;
    
    
    void Update () 
    {
        Vector3 relativePos = (target.position + new Vector3(0, 1.5f, 0)) - transform.position;
        Quaternion rotation = Quaternion.LookRotation(relativePos);
        
        Quaternion current = transform.localRotation;
        
        transform.localRotation = Quaternion.Slerp(current, rotation, Time.deltaTime);
        transform.Translate(0, 0, 3 * Time.deltaTime);
    }
}

And here’s the tutorial that explains how to use it:
http://unity3d.com/learn/tutorials/modules/intermediate/scripting/quaternions

[numberkruncher]

Not sure if this would achieve what you want, but the easy option might be to:

1. Create the following object hierarchy:

   Star
     |--- Planet
   

2. Position the planet relative to the star at desired distance.

3. Create a script which simply rotates Star since Planet will appear to orbit.

[vargata]

here is a little sample code. if you add a rigidbody to your object and play with drags you can set up a pretty orbit. would be better modelling the forces

#pragma strict

var target : Transform;

private var dir : Vector3;
private var forward : Vector3;
private var side : Vector3;
private var cross : Vector3;

function Start () {
	forward = transform.forward; //forward vector just to have it (in 3d you need a plane to calculate normalvector, this will be one side of the plane)
	dir = target.transform.position - transform.position; //direction from your object towards the target object what you will orbit (the other side of the plane)
	side = Vector3.Cross(dir, forward); //90 degrees (normalvector) to the plane closed by the forward and the dir vectors
}

function Update () {
	dir = target.transform.position - transform.position;
	transform.LookAt(dir.normalized); // look at the target
	rigidbody.AddForce(dir.normalized * 50);//add gravity like force pulling your object towards the target
	cross = Vector3.Cross(dir, side); //90 degrees vector to the initial sideway vector (orbit direction) /I use it to make the object orbit horizontal not vertical as the vertical lookatmatrix is flawed/
	rigidbody.AddForce(cross.normalized * 50); //add the force to make your object move (orbit)
}

you need the drag value to work against these forces or your object will fly away on a spiral the bigger the drag the smaller the orbit range