Physics Behaving Differently on Different Devices

Hello!

I'm creating a mobile game where you can pick up and throw game objects. The velocity of the throw depends on how fast the user is moving their finger before letting go. I have a script that does this well, but unfortunately the velocity at which the object is thrown is changes based on the device the player is using. For example the velocity of the thrown object is faster on an iPad Air 2 than on an iPhone 6, and the velocity of the throw is slower on an iPad 2.

I've narrowed down the location of where the problem lies, but I can't seem to figure out how to fix it. Below is the relevant code

Code (CSharp):

1.     Dictionary<int, DragData> draggedObjects;
2.     struct DragData
3.     {
4.         public Transform draggedTransform;
5.         public Rigidbody2D draggedRigidbody;
6.         public HingeJoint2D draggedJoint;
7.      
8.     }
9.  
10.     void init()
11.     {
12.         draggedObjects = new Dictionary<int, DragData>();
13.     }
14.  
15.  
16.  
17.     void FixedUpdate()
18.     {
19.        ...
20.         DragData data = draggedObjects[entry];
21.  
22.         // When object is dragged
23.         if (touch.phase == TouchPhase.Moved ||
24.             touch.phase == TouchPhase.Stationary)
25.         {
26.             // Gets the position of the user touch
27.             Vector3 touchCoords = touch.position;
28.             // Gets the position of the dragged object
29.             Vector3 objectCoords = GetComponent<Camera> ().WorldToScreenPoint(data.draggedTransform.position );          
30.             float distance = Vector2.Distance(objectCoords, touchCoords);
31.             // Drag Damping is a public float
32.             Vector2 objectVelocity = (touchCoords - objectCoords).normalized * (distance / (dragDamping));
33.          
34.             data.draggedJoint.GetComponent<Rigidbody2D>().velocity = objectVelocity;
35.                  
36.         }
37.     }

The velocity set in the final line of code seems to be higher on more advanced devices, but I'm not sure which line of code is causing this or how to fix it. Any help would be greatly appreciated.

 

Thanks so much for the reply Karl, I thought that the screen resolution may have been the culprit. Sorry if this is a dumb question, but how would I go about normalizing the distance? And once again, thanks for the help!

 

Try dividing the distance by the screen dimensions.

 

Thanks for the help guys, I believe it's now working just how I wanted.