Rotate object around other object (or circle) using mouse

Questions & Answers
1

Hi everyone,

As the title suggests I’m trying to rotate an object around another object using the mouse. I’ve managed to rotate a cube around a capsule with this code :

    public float PlanetRotateSpeed = -0.005f;
    public float OrbitSpeed = 0.0005f;
    protected GameObject capsule;
    
    void Start () {
    	capsule = GameObject.Find("capsule"); 
    }
    	
    void Update () {
    	
        	transform.RotateAround (capsule.transform.position, Vector3.forward, OrbitSpeed* Time.deltaTime);
    }

So the cube rotates around the capsule as if it’s moving along a circle (or sphere), what I want to do (and can’t actually do) is keep the cube moving along the circle but not with “OrbitSpeed* Time.deltaTime” but depending on the mouse position.

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10561-unityanswers.png1138×543 27.3 KB

Thanks in advance.

2

As mentioned in my comment, there are multiple different ways of achieving this behavior, but none are simple. It is easier as a 2D game looking down the Z axis.

using UnityEngine;
using System.Collections;

public class Around4 : MonoBehaviour {
	
	public Transform target;
	public float fRadius = 3.0f;
	private Transform pivot;

	void Start() {
		pivot = new GameObject().transform;
		transform.parent = pivot;
	}
	
	void Update () {
		Vector3 v3Pos = Camera.main.WorldToScreenPoint (target.position);
		v3Pos = Input.mousePosition - v3Pos;
		float angle = Mathf.Atan2 (v3Pos.y, v3Pos.x) * Mathf.Rad2Deg;
		
		pivot.position = target.position;
		pivot.rotation = Quaternion.AngleAxis (angle, Vector3.forward);
	}
}

Here is a second way that positions the object on the circle. The object is not rotated, so you would need to add a LookAt() if the object needs to be rotated:

using UnityEngine;
using System.Collections;

public class Around2 : MonoBehaviour {
	
	public Transform target; 
	public float fRadius = 3.0f;
	
	void Update () {
		Vector3 v3Pos = Camera.main.WorldToScreenPoint (target.position);
		v3Pos = Input.mousePosition - v3Pos;
		float angle = Mathf.Atan2 (v3Pos.y, v3Pos.x) * Mathf.Rad2Deg;
		v3Pos = Quaternion.AngleAxis (angle, Vector3.forward) * (Vector3.right * fRadius);
		transform.position = target.position + v3Pos;
	}
}