Question by Belevar · Dec 20, 2017 at 03:02 PM · rotation input unity 2d touch rotate object

Rotate object after swipe according to swipe direction

Hi, I want my 2D object to rotate (look at) mouse/finger on the screen and after releasing input to start rotating.

I have the code which is doing what I need but in some cases it has a little bug that object starts to rotate in wrong direction(like bouncing of invisible wall).

  void LookAtMouse()
     {
         var ray = new Ray2D(transform.position, Input.mousePosition - transform.position);
         var extendedMousePosition = ray.GetPoint(300);
 
         float AngleRad = Mathf.Atan2(extendedMousePosition.y - transform.position.y, extendedMousePosition.x - transform.position.x);
         float AngleDeg = (180 / Mathf.PI) * AngleRad;
 
         var mousePos = Input.mousePosition;
         var newRotation = Quaternion.Euler(0, 0, AngleDeg - ObjectStartAngle - 1);
 
 
         this.transform.rotation = Quaternion.Euler(0, 0, AngleDeg - ObjectStartAngle - 1);
         Debug.DrawLine(transform.position, mousePos, Color.red);
         Debug.DrawLine(transform.position, extendedMousePosition, Color.yellow);
     }

And here is my code to get swipe direction if user will release mouse button:

  void StartRotation()
     {
      
         var ray = new Ray2D(transform.position, Input.mousePosition - transform.position);
         var extendedMousePosition= ray.GetPoint(300);
 
         float AngleRad = Mathf.Atan2(extendedMousePosition.y - transform.position.y, extendedMousePosition.x - transform.position.x);
         // Get Angle in Degrees
         float AngleDeg = (180 / Mathf.PI) * AngleRad;
         // Rotate Object
         var newRoation = Quaternion.Euler(0, 0, AngleDeg - ObjectStartAngle - 1);
 
         swipeDirection = newRoation.eulerAngles - transform.rotation.eulerAngles;
 
         Debug.Log("Object:" + transform.rotation.eulerAngles);
         Debug.Log("Finger:" + newRoation.eulerAngles);
         Debug.Log("Swipe direction" + swipeDirection);
     }

And here is the problem. Sometimes especially during fast swipes or when user will stop movement at the end then swipeDirection is calculated incorrectly. I'm strugling with it for 3 days now and I find out that when the bug occur the object is ahead of mouse which seems to be strange..

Here are some gifs for better understanding. Correct behavior: alt text