DragRigidBody in 2D

Unity Engine
1

Does anyone know how to do this? I’ve searched google and found several scripts, none of which seem to work for me. Thanks in advance.

2

I can’t take any credit for the below, I got it a while back somewhere and it works very well after some minor modifications, just stick this on your camera or empty object and make sure anything you want draggable is in the relevant layer specified in line 25.

using UnityEngine;
using System.Collections;

public class dragIt : MonoBehaviour {
	
	public float distance = 0.2f;
	public float damper = 1.0f;
	public float frequency = 8.0f;
	public float drag = 30.0f; 
	public float angularDrag = 30.0f;
	
	public bool attachToCenterOfMass = false;
	private SpringJoint2D springJoint;
	private Camera mainCamera;
	
	void Start() {
		mainCamera = FindCamera ();
	}
	
	void Update () {		
		
		if (!Input.GetMouseButtonDown (0))
			return;
		
		int layerMask = 1 << 10;
		RaycastHit2D hit = Physics2D.Raycast (mainCamera.ScreenToWorldPoint (Input.mousePosition), Vector2.zero, Mathf.Infinity, layerMask);
		//Debug.Log ("Layermask: " + LayerMask.LayerToName (8));
		// I have proxy collider objects (empty gameobjects with a 2D Collider) as a child of a 3D rigidbody - simulating collisions between 2D and 3D objects
		// I therefore set any 'touchable' object to layer 8 and use the layerMask above for all touchable items
		if(!hit.rigidbody) return;
		if (hit.collider != null  hit.rigidbody.isKinematic == true) {
			return;
		} 
		if (hit.collider != null  hit.rigidbody.isKinematic == false) {
			
			if (!springJoint) {
				GameObject go = new GameObject ("Rigidbody2D Dragger");
				Rigidbody2D body = go.AddComponent ("Rigidbody2D") as Rigidbody2D;
				springJoint = go.AddComponent ("SpringJoint2D") as SpringJoint2D;
				body.isKinematic = true;
				body.mass=0.0001f;
			}
			springJoint.transform.position = hit.point;
			if (attachToCenterOfMass) {
				Debug.Log ("Currently 'centerOfMass' isn't reported for 2D physics like 3D Physics - it will be added in a future release.");
				
				// Currently 'centerOfMass' isn't reported for 2D physics like 3D Physics yet - it will be added in a future release.
				//Vector3 anchor = transform.TransformDirection(hit.rigidbody.centerOfMass) + hit.rigidbody.transform.position; in c# might be Vector2?
				//anchor = springJoint.transform.InverseTransformPoint(anchor);
				//springJoint.anchor = anchor;
			} else {
				//springJoint.anchor = Vector3.zero;
			}
			
			springJoint.distance = distance; // there is no distance in SpringJoint2D
			springJoint.dampingRatio = damper;// there is no damper in SpringJoint2D but there is a dampingRatio
			//springJoint.maxDistance = distance;  // there is no MaxDistance in the SpringJoint2D - but there is a 'distance' field 
			//  see http://docs.unity3d.com/Documentation/ScriptReference/SpringJoint2D.html
			//springJoint.maxDistance = distance;
			springJoint.connectedBody = hit.rigidbody;
			// maybe check if the 'fraction' is normalised. See http://docs.unity3d.com/Documentation/ScriptReference/RaycastHit2D-fraction.html
			StartCoroutine ("DragObject", hit.fraction);
		} // end of hit true condition
	} // end of update
	
	IEnumerator DragObject (float distance) {
		float oldDrag = springJoint.connectedBody.drag;
		float oldAngularDrag = springJoint.connectedBody.angularDrag;
		
		springJoint.connectedBody.drag = drag;
		springJoint.connectedBody.angularDrag = angularDrag;
		Camera mainCamera = FindCamera ();
		
		
		
		while (Input.GetMouseButton (0)) {
			
			Ray ray = mainCamera.ScreenPointToRay (Input.mousePosition);
			springJoint.transform.position = ray.GetPoint (distance);

			yield return null;
		}
		
		if (springJoint.connectedBody) {
			//Debug.Log(springJoint.connectedBody.rigidbody2D.velocity.ToString());
			Vector2 power = springJoint.connectedBody.rigidbody2D.velocity;
			power = power/ (springJoint.connectedBody.rigidbody2D.mass+1);
			//Debug.Log(power.ToString());
			
			springJoint.connectedBody.drag = 0.0f;//oldDrag;
			springJoint.connectedBody.angularDrag = 0.05f;//oldAngularDrag;
			springJoint.connectedBody = null;
		}
	}
	
	Camera FindCamera () {
		if (camera)
			return camera;
		else
			return Camera.main;
	}
}
3

Thanks !

4

I don’t get what I should be changing on line 25, help?

I’m also getting errors “Unexpected symbol ‘hit’”

5

I’m sure you figured this out by now, there are && symbols missing on line 30 and line 34…

Should be:

if (hit.collider != null && hit.rigidbody.isKinematic == true)

cheers!

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