Isometric ball moving in unity 3d. Ball moving in opposite direction

Question

I am making a game in unity 3d. It is a 2.5d game which mean it is in isometric. The game is quite simple. Player drags mouse and a trajectory will be shown just like in angry bird and when player release the mouse the ball will move to the direction. However I am having issue here that once mouse is released the ball moves in exact opposite direction. I am not able to understand what the real issue is. My code is as follows:

For Ball:

public class BallScript : MonoBehaviour

{
    public Rigidbody2D rbg;
    public CircleCollider2D col;

    public Vector3 BallPos{
        get {return transform.position;}
    }


    void Awake(){
        rbg = GetComponent<Rigidbody2D>();
        col = GetComponent<CircleCollider2D>();
    }

    public void PushBall(Vector2 force){
        rbg.AddForce(force,ForceMode2D.Impulse);
    }

    //to enable rigidbody so we can use projectile again
    public void ActivateRb(){
        rbg.isKinematic = false;
    }

    public void DeActivateRb(){
        rbg.velocity = Vector3.zero;
        rbg.angularVelocity = 0f;
        rbg.isKinematic = true;
    }
}

The code for my game manager is as follows:

public class Trajectory : MonoBehaviour
{
    [SerializeField] int dotsNumbers;
    [SerializeField] GameObject dotsParent;
    
    [SerializeField] GameObject DotsPrefab;
    [SerializeField] float dotSpacing;
    Vector2 pos;
    float timeStamp;
    Transform[] dotsList;

    void Start(){
        //hide trajectory in the start
        Hide();

        PrepareDots();
    }

    void PrepareDots(){
        dotsList = new Transform[dotsNumbers];
        for(int i=0;i<dotsNumbers;i++){
            dotsList[i] = Instantiate(DotsPrefab,null).transform;
            dotsList[i].parent = dotsParent.transform;
        }
    }
    public void UpdateDots(Vector3 ballPos,Vector2 forceApplied){
        timeStamp = dotSpacing;
        for(int i=0;i<dotsNumbers;i++){
            pos.x = (ballPos.x + forceApplied.x * timeStamp);
            pos.y = (ballPos.y + forceApplied.y * timeStamp)-(Physics2D.gravity.magnitude * timeStamp * timeStamp)/2f;
            dotsList[i].position = pos;
            timeStamp += dotSpacing;
        }
    }


    public void Show(){
        dotsParent.SetActive(true);
    }
    public void Hide(){
        dotsParent.SetActive(false);
    }
}

Here is the code for gamemanager

// using singleton pattern 
Camera cam;
public BallScript ball;
public Trajectory trajectory;
public static GameManagerScript Instance;
void Awake(){
    if(Instance==null){
        Instance = this;
    }
}


[SerializeField] float pushForce = 4f;
bool isDragging = false;

Vector2 startPoint;
Vector2 endPoint;
Vector2 direction;
 Vector2 force;
float distance;


void Start(){
    cam = Camera.main;
    ball.DeActivateRb();
}

void Update(){
    if(Input.GetMouseButtonDown(0)){
        isDragging = true;
        OnDragStart();
    }
    if(Input.GetMouseButtonUp(0)){
        isDragging = false;
        OnDragEnd();
    }
    if(isDragging){
        OnDrag();
    }
}

void OnDragStart(){
    ball.DeActivateRb();
    startPoint = cam.ScreenToWorldPoint(Input.mousePosition);
    trajectory.Show();
}

void OnDrag(){
    endPoint = cam.ScreenToWorldPoint(Input.mousePosition);
    distance = Vector2.Distance(startPoint,endPoint);
    direction = (endPoint-startPoint).normalized;
    force = direction* distance * pushForce;

    trajectory.UpdateDots(ball.BallPos,force);
    
}

void OnDragEnd(){
    ball.ActivateRb();
    ball.PushBall(force);
    trajectory.Hide();
}

The ball moves in exact opposite direction where I wish to send it by dragging. Is it because of the isometric issue or I am missing something?P.S: have applied negative force as well as in case and have also made change in direction formula

rbg.AddForce(-force,ForceMode2D.Impulse);
direction = (startPoint-endPoint).normalized;

Answer 1

Some suggestions:

When you call ScreenToWorldPoint(), you generally should not pass in the mouse position directly. You need to set the z-position first. For example,

Vector3 mousePosition = Input.mousePosition;
mousePosition.z = cam.nearClipPlane;
endPoint = cam.ScreenToWorldPoint(mousePosition);

This part of your OnDrag() is pointlessly complicated:

distance = Vector2.Distance(startPoint,endPoint);
direction = (endPoint-startPoint).normalized;
force = direction* distance * pushForce;

Let's analyze what you're doing here:

1. Calculate the scalar distance.
2. Get the Vector3 from startPoint to endPoint
3. Normalize the Vector3 from step 2 to get a direction.
4. Multiply the distance from step 1 and direction from step 3 to get the Vector3 from startPoint to endPoint.

Hold on a minute - the value you end up with in step 4 is the same value you got in step 2. You don't need the other steps! This can be simplified to

force = (endPoint - startPoint) * pushForce;