problem with ScreenToWorldPoint (keep getting the same coordinates)

Question

I wrote a code to move my player to the touch position :

 public class Movment : MonoBehaviour
 {
     public Vector2 touch;
     public Transform Player;
     new Vector3 vec;
 
     // Update is called once per frame
     
     void Update()
     {
         for (int i = 0; i < Input.touchCount; i++)
         {
             touch = Camera.main.ScreenToWorldPoint(Input.touches[i].position);
             vec = new Vector3(touch.x, touch.y, 5);
             Debug.DrawLine(Vector3.zero, vec, Color.red);
             Debug.Log(vec);
             Player.position = vec;
         }   
     }
 }

it keeps giving me (-3.7, 3.5, 5.0) I spent 2 hours reading solutions and answers (like setting a z coordinate to the vector3) but nothing solved it

Answer 1

You are passing a Vector2 (touch.position) to ScreenToWorldPoint, which takes a Vector3 input. This will end up casting to a Vector3 with an assumed z-coordinate of 0, which means the function will always return the camera's position regardless of the screen point. If you want to find the world space position of a point on screen with a set z-position, you can use a plane-raycast;

 //This is the world space z-coord of the points
 float zPosition = 5f;
 
 if (Input.touchCount > 0)
 {
     //Z-Position is irrelevant with ScreenPointToRay
     Ray ray = Camera.main.ScreenPointToRay (Input.GetTouch (0).position);
     //Create a new plane on the z-axis
     Plane plane = new Plane (new Vector3 (0f, 0f, -1f), new Vector3 (0f, 0f, zPosition));
 
     //Raycast against the plane
     if (plane.Raycast (ray, out float hit))
     {
         //Find the world pos of our screen point on the plane
         Vector3 hitPos = ray.GetPoint (hit);
         Player.position = hitPos;
     }
 }

problem with ScreenToWorldPoint (keep getting the same coordinates)

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